use serde::Serialize;
use std::{
    collections::BTreeMap,
    ffi::{OsStr, OsString},
    path::{Path, PathBuf},
    process::Command,
};

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
#[serde(rename_all = "lowercase")]
pub enum FileStatusKind {
    Modified,
    Added,
    Deleted,
    Renamed,
    Untracked,
    Conflicted,
    Unknown,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct GitFileStatus {
    pub path: String,
    pub old_path: Option<String>,
    pub staged: Option<FileStatusKind>,
    pub unstaged: Option<FileStatusKind>,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct GitStatus {
    pub repo_path: String,
    pub current_branch: Option<String>,
    pub upstream: Option<String>,
    pub ahead: u32,
    pub behind: u32,
    pub files: Vec<GitFileStatus>,
    pub clean: bool,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct GitBranch {
    pub name: String,
    pub current: bool,
    pub remote: bool,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct GitCommit {
    pub hash: String,
    pub short_hash: String,
    pub summary: String,
    pub author_name: String,
    pub author_email: String,
    pub date: String,
    pub refs: Vec<String>,
    pub files: Vec<GitCommitFile>,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct GitCommitFile {
    pub path: String,
    pub old_path: Option<String>,
    pub status: FileStatusKind,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct GitRepositoryFile {
    pub path: String,
    pub tracked: bool,
    pub status: Option<FileStatusKind>,
}

#[derive(Debug, Default, Clone, PartialEq, Eq)]
struct BranchInfo {
    current_branch: Option<String>,
    upstream: Option<String>,
    ahead: u32,
    behind: u32,
}

#[derive(Debug, Clone, PartialEq, Eq)]
enum CheckoutPlan {
    Local(String),
    TrackRemote { local: String, remote: String },
    Raw(String),
}

#[tauri::command]
pub fn open_repository(path: String) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    status_for_repo(&repo)
}

#[tauri::command]
pub fn get_status(path: String) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    status_for_repo(&repo)
}

#[tauri::command]
pub fn list_branches(path: String) -> Result<Vec<GitBranch>, String> {
    let repo = resolve_repo(&path)?;
    let output = run_git(
        &repo,
        [
            "for-each-ref",
            "--format=%(refname)\t%(HEAD)",
            "refs/heads",
            "refs/remotes",
        ],
    )?;
    let text = String::from_utf8_lossy(&output);
    let mut branches = Vec::new();

    for line in text.lines() {
        let Some((ref_name, head_marker)) = line.split_once('\t') else {
            continue;
        };

        let (name, remote) = if let Some(name) = ref_name.strip_prefix("refs/heads/") {
            (name, false)
        } else if let Some(name) = ref_name.strip_prefix("refs/remotes/") {
            if name.ends_with("/HEAD") {
                continue;
            }
            (name, true)
        } else {
            continue;
        };

        branches.push(GitBranch {
            name: name.to_string(),
            current: head_marker.trim() == "*",
            remote,
        });
    }

    Ok(branches)
}

#[tauri::command]
pub fn checkout_branch(path: String, branch: String) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    let branch = branch.trim().to_string();
    if branch.is_empty() {
        return Err("Branch-Name darf nicht leer sein.".to_string());
    }

    match checkout_plan(&repo, &branch)? {
        CheckoutPlan::Local(local) => {
            run_git(&repo, ["checkout", local.as_str()])?;
        }
        CheckoutPlan::TrackRemote { local, remote } => {
            run_git(
                &repo,
                ["checkout", "--track", "-b", local.as_str(), remote.as_str()],
            )?;
        }
        CheckoutPlan::Raw(target) => {
            run_git(&repo, ["checkout", target.as_str()])?;
        }
    }

    status_for_repo(&repo)
}

#[tauri::command]
pub fn stage_files(path: String, files: Vec<String>) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    validate_files(&files)?;

    if !files.is_empty() {
        run_git_with_paths(&repo, &["add"], &files)?;
    }

    status_for_repo(&repo)
}

#[tauri::command]
pub fn unstage_files(path: String, files: Vec<String>) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    validate_files(&files)?;

    if !files.is_empty() {
        let current_status = status_for_repo(&repo)?;
        unstage_selected_files(&repo, &current_status.files, &files)?;
    }

    status_for_repo(&repo)
}

#[tauri::command]
pub fn restore_files(path: String, files: Vec<String>, staged: bool) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    validate_files(&files)?;

    if files.is_empty() {
        return status_for_repo(&repo);
    }

    let current_status = status_for_repo(&repo)?;
    if staged {
        restore_staged_files(&repo, &current_status.files, &files)?;
    } else {
        restore_worktree_files(&repo, &current_status.files, &files)?;
    }

    status_for_repo(&repo)
}

#[tauri::command]
pub fn commit(path: String, message: String) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    if message.trim().is_empty() {
        return Err("Commit-Message darf nicht leer sein.".to_string());
    }

    run_git(&repo, ["commit", "-m", message.as_str()])?;
    status_for_repo(&repo)
}

#[tauri::command]
pub fn pull(path: String) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    run_git(&repo, ["pull", "--ff-only"])?;
    status_for_repo(&repo)
}

#[tauri::command]
pub fn push(path: String) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    run_git(&repo, ["push"])?;
    status_for_repo(&repo)
}

#[tauri::command]
pub fn merge_branch(path: String, branch: String) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    let branch = branch.trim();
    if branch.is_empty() {
        return Err("Branch-Name darf nicht leer sein.".to_string());
    }

    run_git(&repo, ["merge", "--no-edit", branch])?;
    status_for_repo(&repo)
}

#[tauri::command]
pub fn list_commits(path: String, limit: Option<u32>) -> Result<Vec<GitCommit>, String> {
    let repo = resolve_repo(&path)?;
    if verify_commit(&repo, "HEAD").is_err() {
        return Ok(Vec::new());
    }

    let limit = limit.unwrap_or(100).clamp(1, 500).to_string();
    let output = run_git(
        &repo,
        [
            "log",
            "--decorate=short",
            "--pretty=format:%H%x1f%h%x1f%an%x1f%ae%x1f%aI%x1f%D%x1f%s%x1e",
            "-n",
            limit.as_str(),
        ],
    )?;

    parse_commit_log(&repo, &output)
}

#[tauri::command]
pub fn list_repository_files(path: String) -> Result<Vec<GitRepositoryFile>, String> {
    let repo = resolve_repo(&path)?;
    repository_files(&repo)
}

#[tauri::command]
pub fn list_file_history(
    path: String,
    file: String,
    limit: Option<u32>,
) -> Result<Vec<GitCommit>, String> {
    let repo = resolve_repo(&path)?;
    validate_files(std::slice::from_ref(&file))?;

    if verify_commit(&repo, "HEAD").is_err() {
        return Ok(Vec::new());
    }

    let limit = limit.unwrap_or(100).clamp(1, 500).to_string();
    let mut args = vec![
        OsString::from("log"),
        OsString::from("--decorate=short"),
        OsString::from("--pretty=format:%H%x1f%h%x1f%an%x1f%ae%x1f%aI%x1f%D%x1f%s%x1e"),
        OsString::from("-n"),
        OsString::from(limit),
    ];
    if !is_repository_folder_path(&repo, &file)? {
        args.push(OsString::from("--follow"));
    }
    args.extend([OsString::from("--"), OsString::from(file)]);
    let output = run_git(&repo, args)?;

    parse_commit_log(&repo, &output)
}

#[tauri::command]
pub fn restore_to_commit(path: String, commit: String) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    let commit_hash = verify_commit(&repo, &commit)?;

    run_git(&repo, ["reset", "--hard", commit_hash.as_str()])?;
    status_for_repo(&repo)
}

#[tauri::command]
pub fn restore_file_from_commit(
    path: String,
    commit: String,
    file: String,
) -> Result<GitStatus, String> {
    let repo = resolve_repo(&path)?;
    validate_files(std::slice::from_ref(&file))?;
    let commit_hash = verify_commit(&repo, &commit)?;

    run_git_with_paths(
        &repo,
        &["restore", "--source", commit_hash.as_str(), "--worktree"],
        &[file],
    )?;
    status_for_repo(&repo)
}

fn resolve_repo(path: &str) -> Result<PathBuf, String> {
    if path.trim().is_empty() {
        return Err("Repository-Pfad darf nicht leer sein.".to_string());
    }

    let input = PathBuf::from(path);
    let output = run_git_at(
        &input,
        ["rev-parse", "--show-toplevel"],
        "Kein Git-Repository oder nicht erreichbar",
    )?;
    let top_level = String::from_utf8_lossy(&output).trim().to_string();

    if top_level.is_empty() {
        return Err("Git konnte keinen Repository-Wurzelpfad ermitteln.".to_string());
    }

    Ok(PathBuf::from(top_level))
}

fn verify_commit(repo: &Path, commit: &str) -> Result<String, String> {
    let commit = commit.trim();
    if commit.is_empty() {
        return Err("Commit darf nicht leer sein.".to_string());
    }

    let rev = format!("{commit}^{{commit}}");
    let output = run_git(repo, ["rev-parse", "--verify", "--quiet", rev.as_str()])
        .map_err(|err| format!("Commit konnte nicht gefunden werden: {err}"))?;
    let hash = String::from_utf8_lossy(&output).trim().to_string();

    if hash.is_empty() {
        return Err("Commit konnte nicht gefunden werden.".to_string());
    }

    Ok(hash)
}

fn status_for_repo(repo: &Path) -> Result<GitStatus, String> {
    let output = run_git(
        repo,
        [
            "status",
            "--porcelain=v1",
            "-b",
            "-z",
            "--untracked-files=all",
        ],
    )?;
    let (branch, files) = parse_status_output(&output)?;

    Ok(GitStatus {
        repo_path: repo.to_string_lossy().to_string(),
        current_branch: branch.current_branch,
        upstream: branch.upstream,
        ahead: branch.ahead,
        behind: branch.behind,
        clean: files.is_empty(),
        files,
    })
}

fn repository_files(repo: &Path) -> Result<Vec<GitRepositoryFile>, String> {
    let status = status_for_repo(repo)?;
    let mut files = BTreeMap::<String, GitRepositoryFile>::new();

    let tracked_output = run_git(repo, ["ls-files", "-z", "--cached", "--deleted"])?;
    for path in parse_nul_paths(&tracked_output) {
        let status = status_for_file(&status.files, &path);
        files.insert(
            path.clone(),
            GitRepositoryFile {
                path,
                tracked: true,
                status,
            },
        );
    }

    let untracked_output = run_git(repo, ["ls-files", "-z", "--others", "--exclude-standard"])?;
    for path in parse_nul_paths(&untracked_output) {
        let status = status_for_file(&status.files, &path).or(Some(FileStatusKind::Untracked));
        files.insert(
            path.clone(),
            GitRepositoryFile {
                path,
                tracked: false,
                status,
            },
        );
    }

    Ok(files.into_values().collect())
}

fn is_repository_folder_path(repo: &Path, path: &str) -> Result<bool, String> {
    let normalized = normalize_git_path(path);
    if repo.join(path).is_dir() {
        return Ok(true);
    }

    let prefix = format!("{normalized}/");
    let tracked_output = run_git(repo, ["ls-files", "-z", "--cached", "--deleted"])?;
    Ok(parse_nul_paths(&tracked_output)
        .iter()
        .any(|tracked_path| normalize_git_path(tracked_path).starts_with(&prefix)))
}

fn normalize_git_path(path: &str) -> String {
    path.replace('\\', "/").trim_matches('/').to_string()
}

fn parse_nul_paths(output: &[u8]) -> Vec<String> {
    output
        .split(|byte| *byte == 0)
        .filter(|entry| !entry.is_empty())
        .map(|entry| String::from_utf8_lossy(entry).to_string())
        .collect()
}

fn status_for_file(statuses: &[GitFileStatus], path: &str) -> Option<FileStatusKind> {
    let status = find_status(statuses, path)?;

    if matches!(status.staged, Some(FileStatusKind::Conflicted))
        || matches!(status.unstaged, Some(FileStatusKind::Conflicted))
    {
        return Some(FileStatusKind::Conflicted);
    }

    status.unstaged.or(status.staged)
}

fn parse_commit_log(repo: &Path, output: &[u8]) -> Result<Vec<GitCommit>, String> {
    const FIELD_SEPARATOR: char = '\x1f';
    const RECORD_SEPARATOR: char = '\x1e';

    let text = String::from_utf8_lossy(output);
    let mut commits = Vec::new();

    for record in text.split(RECORD_SEPARATOR).map(str::trim) {
        if record.is_empty() {
            continue;
        }

        let fields: Vec<&str> = record.splitn(7, FIELD_SEPARATOR).collect();
        if fields.len() != 7 {
            return Err(format!("Unerwarteter Git-Log-Eintrag: {record}"));
        }

        let refs = fields[5]
            .split(',')
            .map(str::trim)
            .filter(|item| !item.is_empty())
            .map(ToString::to_string)
            .collect();

        let hash = fields[0].to_string();
        let files = commit_files(repo, &hash)?;

        commits.push(GitCommit {
            hash,
            short_hash: fields[1].to_string(),
            author_name: fields[2].to_string(),
            author_email: fields[3].to_string(),
            date: fields[4].to_string(),
            refs,
            summary: fields[6].to_string(),
            files,
        });
    }

    Ok(commits)
}

#[cfg(test)]
fn parse_commit_log_metadata(output: &[u8]) -> Result<Vec<GitCommit>, String> {
    const FIELD_SEPARATOR: char = '\x1f';
    const RECORD_SEPARATOR: char = '\x1e';

    let text = String::from_utf8_lossy(output);
    let mut commits = Vec::new();

    for record in text.split(RECORD_SEPARATOR).map(str::trim) {
        if record.is_empty() {
            continue;
        }

        let fields: Vec<&str> = record.splitn(7, FIELD_SEPARATOR).collect();
        if fields.len() != 7 {
            return Err(format!("Unerwarteter Git-Log-Eintrag: {record}"));
        }

        let refs = fields[5]
            .split(',')
            .map(str::trim)
            .filter(|item| !item.is_empty())
            .map(ToString::to_string)
            .collect();

        commits.push(GitCommit {
            hash: fields[0].to_string(),
            short_hash: fields[1].to_string(),
            author_name: fields[2].to_string(),
            author_email: fields[3].to_string(),
            date: fields[4].to_string(),
            refs,
            summary: fields[6].to_string(),
            files: Vec::new(),
        });
    }

    Ok(commits)
}

fn commit_files(repo: &Path, commit: &str) -> Result<Vec<GitCommitFile>, String> {
    let output = run_git(
        repo,
        [
            "diff-tree",
            "--root",
            "--no-commit-id",
            "--name-status",
            "-r",
            "-M",
            "-z",
            commit,
        ],
    )?;

    parse_commit_files(&output)
}

fn parse_commit_files(output: &[u8]) -> Result<Vec<GitCommitFile>, String> {
    let entries: Vec<&[u8]> = output
        .split(|byte| *byte == 0)
        .filter(|entry| !entry.is_empty())
        .collect();

    let mut files = Vec::new();
    let mut index = 0;

    while index < entries.len() {
        let status_text = String::from_utf8_lossy(entries[index]).to_string();
        index += 1;
        let status = map_name_status(&status_text);

        if index >= entries.len() {
            return Err(format!("Git-Diff-Eintrag ohne Pfad: {status_text}"));
        }

        if matches!(status, FileStatusKind::Renamed) {
            let old_path = String::from_utf8_lossy(entries[index]).to_string();
            index += 1;

            if index >= entries.len() {
                return Err(format!("Git-Rename ohne Zielpfad: {old_path}"));
            }

            let path = String::from_utf8_lossy(entries[index]).to_string();
            index += 1;
            files.push(GitCommitFile {
                path,
                old_path: Some(old_path),
                status,
            });
        } else {
            let path = String::from_utf8_lossy(entries[index]).to_string();
            index += 1;
            files.push(GitCommitFile {
                path,
                old_path: None,
                status,
            });
        }
    }

    Ok(files)
}

fn map_name_status(status: &str) -> FileStatusKind {
    match status.chars().next() {
        Some('M') => FileStatusKind::Modified,
        Some('A') => FileStatusKind::Added,
        Some('D') => FileStatusKind::Deleted,
        Some('R') => FileStatusKind::Renamed,
        Some('C') => FileStatusKind::Added,
        Some('U') => FileStatusKind::Conflicted,
        _ => FileStatusKind::Unknown,
    }
}

fn checkout_plan(repo: &Path, branch: &str) -> Result<CheckoutPlan, String> {
    if ref_exists(repo, &format!("refs/heads/{branch}"))? {
        return Ok(CheckoutPlan::Local(branch.to_string()));
    }

    if ref_exists(repo, &format!("refs/remotes/{branch}"))? {
        let Some(local) = local_branch_name_for_remote(branch) else {
            return Ok(CheckoutPlan::Raw(branch.to_string()));
        };

        if ref_exists(repo, &format!("refs/heads/{local}"))? {
            return Ok(CheckoutPlan::Local(local.to_string()));
        }

        return Ok(CheckoutPlan::TrackRemote {
            local: local.to_string(),
            remote: branch.to_string(),
        });
    }

    Ok(CheckoutPlan::Raw(branch.to_string()))
}

fn local_branch_name_for_remote(remote_branch: &str) -> Option<&str> {
    remote_branch
        .split_once('/')
        .map(|(_, local)| local)
        .filter(|local| !local.is_empty())
}

fn ref_exists(repo: &Path, ref_name: &str) -> Result<bool, String> {
    let output = Command::new("git")
        .arg("-C")
        .arg(repo)
        .args(["show-ref", "--verify", "--quiet", ref_name])
        .output()
        .map_err(|err| format!("Git konnte nicht gestartet werden. Ist Git installiert? {err}"))?;

    match output.status.code() {
        Some(0) => Ok(true),
        Some(1) => Ok(false),
        _ => {
            let stderr = String::from_utf8_lossy(&output.stderr);
            let details = if stderr.trim().is_empty() {
                "unbekannter Fehler".to_string()
            } else {
                stderr.trim().to_string()
            };
            Err(format!("Git-Ref konnte nicht geprueft werden: {details}"))
        }
    }
}

fn restore_worktree_files(
    repo: &Path,
    statuses: &[GitFileStatus],
    files: &[String],
) -> Result<(), String> {
    let mut restore_paths = Vec::new();
    let mut clean_paths = Vec::new();

    for file in files {
        let status = find_status(statuses, file);
        if matches!(
            status.and_then(|entry| entry.unstaged),
            Some(FileStatusKind::Untracked)
        ) {
            clean_paths.push(file.clone());
        } else {
            restore_paths.push(file.clone());
        }
    }

    if !restore_paths.is_empty() {
        run_git_with_paths(repo, &["restore", "--worktree"], &restore_paths)?;
    }

    if !clean_paths.is_empty() {
        run_git_with_paths(repo, &["clean", "-fd"], &clean_paths)?;
    }

    Ok(())
}

fn unstage_selected_files(
    repo: &Path,
    statuses: &[GitFileStatus],
    files: &[String],
) -> Result<(), String> {
    let mut restore_paths = Vec::new();
    let mut remove_from_index = Vec::new();

    for file in files {
        let status = find_status(statuses, file);
        if matches!(
            status.and_then(|entry| entry.staged),
            Some(FileStatusKind::Added)
        ) && status.and_then(|entry| entry.old_path.as_ref()).is_none()
        {
            remove_from_index.push(file.clone());
        } else {
            restore_paths.push(file.clone());
        }
    }

    if !restore_paths.is_empty() {
        run_git_with_paths(repo, &["restore", "--staged"], &restore_paths)?;
    }

    if !remove_from_index.is_empty() {
        run_git_with_paths(repo, &["rm", "--cached", "-f"], &remove_from_index)?;
    }

    Ok(())
}

fn restore_staged_files(
    repo: &Path,
    statuses: &[GitFileStatus],
    files: &[String],
) -> Result<(), String> {
    let mut restore_paths = Vec::new();
    let mut remove_from_index = Vec::new();
    let mut clean_paths = Vec::new();

    for file in files {
        let status = find_status(statuses, file);
        match status.and_then(|entry| entry.staged) {
            Some(FileStatusKind::Added) => {
                let target = status
                    .map(|entry| entry.path.clone())
                    .unwrap_or_else(|| file.clone());
                remove_from_index.push(target.clone());
                clean_paths.push(target);
            }
            Some(FileStatusKind::Renamed) => {
                if let Some(entry) = status {
                    if let Some(old_path) = entry.old_path.clone() {
                        restore_paths.push(old_path);
                        remove_from_index.push(entry.path.clone());
                        clean_paths.push(entry.path.clone());
                    } else {
                        restore_paths.push(entry.path.clone());
                    }
                } else {
                    restore_paths.push(file.clone());
                }
            }
            Some(_) => {
                if let Some(entry) = status {
                    restore_paths.push(entry.path.clone());
                } else {
                    restore_paths.push(file.clone());
                }
            }
            None => {
                if matches!(
                    status.and_then(|entry| entry.unstaged),
                    Some(FileStatusKind::Untracked)
                ) {
                    clean_paths.push(file.clone());
                } else {
                    restore_paths.push(file.clone());
                }
            }
        }
    }

    if !restore_paths.is_empty() {
        run_git_with_paths(
            repo,
            &["restore", "--source=HEAD", "--staged", "--worktree"],
            &restore_paths,
        )?;
    }

    if !remove_from_index.is_empty() {
        run_git_with_paths(repo, &["rm", "--cached", "-f"], &remove_from_index)?;
    }

    if !clean_paths.is_empty() {
        run_git_with_paths(repo, &["clean", "-fd"], &clean_paths)?;
    }

    Ok(())
}

fn find_status<'a>(statuses: &'a [GitFileStatus], file: &str) -> Option<&'a GitFileStatus> {
    statuses
        .iter()
        .find(|entry| entry.path == file || entry.old_path.as_deref() == Some(file))
}

fn validate_files(files: &[String]) -> Result<(), String> {
    if files.iter().any(|file| file.is_empty()) {
        return Err("Dateiliste enthaelt einen leeren Pfad.".to_string());
    }
    Ok(())
}

fn run_git_with_paths(
    repo: &Path,
    base_args: &[&str],
    files: &[String],
) -> Result<Vec<u8>, String> {
    let mut args = Vec::with_capacity(base_args.len() + files.len() + 1);
    args.extend(base_args.iter().map(OsString::from));
    args.push(OsString::from("--"));
    args.extend(files.iter().map(OsString::from));
    run_git(repo, args)
}

fn run_git<I, S>(repo: &Path, args: I) -> Result<Vec<u8>, String>
where
    I: IntoIterator<Item = S>,
    S: AsRef<OsStr>,
{
    run_git_at(repo, args, "Git-Befehl fehlgeschlagen")
}

fn run_git_at<I, S>(path: &Path, args: I, context: &str) -> Result<Vec<u8>, String>
where
    I: IntoIterator<Item = S>,
    S: AsRef<OsStr>,
{
    let output = Command::new("git")
        .arg("-C")
        .arg(path)
        .args(args)
        .output()
        .map_err(|err| format!("Git konnte nicht gestartet werden. Ist Git installiert? {err}"))?;

    if output.status.success() {
        return Ok(output.stdout);
    }

    let stderr = String::from_utf8_lossy(&output.stderr);
    let stdout = String::from_utf8_lossy(&output.stdout);
    let details = if !stderr.trim().is_empty() {
        stderr.trim()
    } else if !stdout.trim().is_empty() {
        stdout.trim()
    } else {
        "unbekannter Fehler"
    };

    Err(format!("{context}: {details}"))
}

fn parse_status_output(output: &[u8]) -> Result<(BranchInfo, Vec<GitFileStatus>), String> {
    let entries: Vec<&[u8]> = output
        .split(|byte| *byte == 0)
        .filter(|entry| !entry.is_empty())
        .collect();

    let mut index = 0;
    let mut branch = BranchInfo::default();

    if let Some(first) = entries.first() {
        if first.starts_with(b"## ") {
            branch = parse_branch_header(&String::from_utf8_lossy(first));
            index = 1;
        }
    }

    let mut files = Vec::new();
    while index < entries.len() {
        let entry = String::from_utf8_lossy(entries[index]);
        index += 1;

        if entry.len() < 4 {
            return Err(format!("Unerwartete Git-Statuszeile: {entry}"));
        }

        let bytes = entry.as_bytes();
        let staged_code = bytes[0] as char;
        let unstaged_code = bytes[1] as char;
        let path = entry[3..].to_string();

        let old_path = if is_rename_or_copy(staged_code) || is_rename_or_copy(unstaged_code) {
            if index >= entries.len() {
                return Err(format!("Git-Status fuer Rename ohne Ursprungspfad: {path}"));
            }
            let old_path = String::from_utf8_lossy(entries[index]).to_string();
            index += 1;
            Some(old_path)
        } else {
            None
        };

        let (staged, unstaged) = map_status_codes(staged_code, unstaged_code);
        files.push(GitFileStatus {
            path,
            old_path,
            staged,
            unstaged,
        });
    }

    Ok((branch, files))
}

fn parse_branch_header(header: &str) -> BranchInfo {
    let mut info = BranchInfo::default();
    let header = header.trim().strip_prefix("## ").unwrap_or(header).trim();

    let (branch_part, tracking_part) = if let Some(start) = header.rfind(" [") {
        if header.ends_with(']') {
            (&header[..start], Some(&header[start + 2..header.len() - 1]))
        } else {
            (header, None)
        }
    } else {
        (header, None)
    };

    if let Some(tracking) = tracking_part {
        for item in tracking.split(',').map(str::trim) {
            if let Some(value) = item.strip_prefix("ahead ") {
                info.ahead = value.parse().unwrap_or(0);
            } else if let Some(value) = item.strip_prefix("behind ") {
                info.behind = value.parse().unwrap_or(0);
            }
        }
    }

    if let Some(branch_name) = branch_part.strip_prefix("No commits yet on ") {
        info.current_branch = Some(branch_name.to_string());
        return info;
    }

    if branch_part == "HEAD (no branch)" {
        return info;
    }

    if let Some((current, upstream)) = branch_part.split_once("...") {
        if !current.is_empty() {
            info.current_branch = Some(current.to_string());
        }
        if !upstream.is_empty() {
            info.upstream = Some(upstream.to_string());
        }
    } else if !branch_part.is_empty() {
        info.current_branch = Some(branch_part.to_string());
    }

    info
}

fn map_status_codes(
    staged_code: char,
    unstaged_code: char,
) -> (Option<FileStatusKind>, Option<FileStatusKind>) {
    if is_conflict(staged_code, unstaged_code) {
        return (
            Some(FileStatusKind::Conflicted),
            Some(FileStatusKind::Conflicted),
        );
    }

    if staged_code == '?' && unstaged_code == '?' {
        return (None, Some(FileStatusKind::Untracked));
    }

    (
        map_index_status(staged_code),
        map_worktree_status(unstaged_code),
    )
}

fn map_index_status(code: char) -> Option<FileStatusKind> {
    match code {
        ' ' => None,
        'M' => Some(FileStatusKind::Modified),
        'A' => Some(FileStatusKind::Added),
        'D' => Some(FileStatusKind::Deleted),
        'R' => Some(FileStatusKind::Renamed),
        'C' => Some(FileStatusKind::Added),
        _ => Some(FileStatusKind::Unknown),
    }
}

fn map_worktree_status(code: char) -> Option<FileStatusKind> {
    match code {
        ' ' => None,
        'M' => Some(FileStatusKind::Modified),
        'A' => Some(FileStatusKind::Added),
        'D' => Some(FileStatusKind::Deleted),
        'R' => Some(FileStatusKind::Renamed),
        'C' => Some(FileStatusKind::Added),
        _ => Some(FileStatusKind::Unknown),
    }
}

fn is_rename_or_copy(code: char) -> bool {
    matches!(code, 'R' | 'C')
}

fn is_conflict(staged_code: char, unstaged_code: char) -> bool {
    matches!(
        (staged_code, unstaged_code),
        ('D', 'D') | ('A', 'U') | ('U', 'D') | ('U', 'A') | ('D', 'U') | ('A', 'A') | ('U', 'U')
    )
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::{
        ffi::OsStr,
        fs,
        path::{Path, PathBuf},
        time::{SystemTime, UNIX_EPOCH},
    };

    struct TempRepo {
        path: PathBuf,
    }

    impl Drop for TempRepo {
        fn drop(&mut self) {
            let _ = fs::remove_dir_all(&self.path);
        }
    }

    fn init_temp_repo(name: &str) -> TempRepo {
        let nanos = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .expect("system time should be after Unix epoch")
            .as_nanos();
        let path = std::env::temp_dir().join(format!(
            "tauri_git_lite_{name}_{}_{}",
            std::process::id(),
            nanos
        ));

        fs::create_dir_all(&path).expect("temp repo directory should be created");
        run_git_test(&path, ["init", "-q"]);
        run_git_test(&path, ["config", "user.email", "test@example.com"]);
        run_git_test(&path, ["config", "user.name", "Tester"]);

        TempRepo { path }
    }

    fn run_git_test<I, S>(repo: &Path, args: I)
    where
        I: IntoIterator<Item = S>,
        S: AsRef<OsStr>,
    {
        let output = Command::new("git")
            .arg("-C")
            .arg(repo)
            .args(args)
            .output()
            .expect("git should start");

        assert!(
            output.status.success(),
            "git command failed with status {}\nstdout: {}\nstderr: {}",
            output.status,
            String::from_utf8_lossy(&output.stdout),
            String::from_utf8_lossy(&output.stderr)
        );
    }

    fn git_output_test<I, S>(repo: &Path, args: I) -> String
    where
        I: IntoIterator<Item = S>,
        S: AsRef<OsStr>,
    {
        let output = Command::new("git")
            .arg("-C")
            .arg(repo)
            .args(args)
            .output()
            .expect("git should start");

        assert!(
            output.status.success(),
            "git command failed with status {}\nstdout: {}\nstderr: {}",
            output.status,
            String::from_utf8_lossy(&output.stdout),
            String::from_utf8_lossy(&output.stderr)
        );

        String::from_utf8_lossy(&output.stdout).trim().to_string()
    }

    fn commit_initial_file(repo: &Path) {
        fs::write(repo.join("old.txt"), "original\n").expect("initial file should be written");
        run_git_test(repo, ["add", "old.txt"]);
        run_git_test(repo, ["commit", "-q", "-m", "init"]);
    }

    #[test]
    fn parses_branch_tracking_and_file_states() {
        let raw = b"## main...origin/main [ahead 2, behind 1]\0 M changed.txt\0D  deleted.txt\0?? new.txt\0";
        let (branch, files) = parse_status_output(raw).unwrap();

        assert_eq!(branch.current_branch.as_deref(), Some("main"));
        assert_eq!(branch.upstream.as_deref(), Some("origin/main"));
        assert_eq!(branch.ahead, 2);
        assert_eq!(branch.behind, 1);
        assert_eq!(
            files,
            vec![
                GitFileStatus {
                    path: "changed.txt".to_string(),
                    old_path: None,
                    staged: None,
                    unstaged: Some(FileStatusKind::Modified),
                },
                GitFileStatus {
                    path: "deleted.txt".to_string(),
                    old_path: None,
                    staged: Some(FileStatusKind::Deleted),
                    unstaged: None,
                },
                GitFileStatus {
                    path: "new.txt".to_string(),
                    old_path: None,
                    staged: None,
                    unstaged: Some(FileStatusKind::Untracked),
                },
            ]
        );
    }

    #[test]
    fn parses_z_renames_with_current_path_first() {
        let raw = b"## feature\0R  new-name.txt\0old-name.txt\0";
        let (_, files) = parse_status_output(raw).unwrap();

        assert_eq!(
            files,
            vec![GitFileStatus {
                path: "new-name.txt".to_string(),
                old_path: Some("old-name.txt".to_string()),
                staged: Some(FileStatusKind::Renamed),
                unstaged: None,
            }]
        );
    }

    #[test]
    fn parses_conflicts_as_conflicted() {
        let raw = b"## main\0UU conflicted.txt\0";
        let (_, files) = parse_status_output(raw).unwrap();

        assert_eq!(files[0].staged, Some(FileStatusKind::Conflicted));
        assert_eq!(files[0].unstaged, Some(FileStatusKind::Conflicted));
    }

    #[test]
    fn parses_initial_branch_header() {
        let branch = parse_branch_header("## No commits yet on main");

        assert_eq!(branch.current_branch.as_deref(), Some("main"));
        assert_eq!(branch.upstream, None);
        assert_eq!(branch.ahead, 0);
        assert_eq!(branch.behind, 0);
    }

    #[test]
    fn parses_commit_history_records() {
        let raw = b"1111111111111111111111111111111111111111\x1f1111111\x1fAda Lovelace\x1fada@example.com\x1f2026-06-26T12:34:56+02:00\x1fHEAD -> main, tag: v1\x1fAdd history panel\x1e";
        let commits = parse_commit_log_metadata(raw).unwrap();

        assert_eq!(
            commits,
            vec![GitCommit {
                hash: "1111111111111111111111111111111111111111".to_string(),
                short_hash: "1111111".to_string(),
                author_name: "Ada Lovelace".to_string(),
                author_email: "ada@example.com".to_string(),
                date: "2026-06-26T12:34:56+02:00".to_string(),
                refs: vec!["HEAD -> main".to_string(), "tag: v1".to_string()],
                summary: "Add history panel".to_string(),
                files: Vec::new(),
            }]
        );
    }

    #[test]
    fn parses_commit_file_changes_and_renames() {
        let raw = b"M\0src/main.rs\0A\0README.md\0R100\0old.txt\0new.txt\0";
        let files = parse_commit_files(raw).unwrap();

        assert_eq!(
            files,
            vec![
                GitCommitFile {
                    path: "src/main.rs".to_string(),
                    old_path: None,
                    status: FileStatusKind::Modified,
                },
                GitCommitFile {
                    path: "README.md".to_string(),
                    old_path: None,
                    status: FileStatusKind::Added,
                },
                GitCommitFile {
                    path: "new.txt".to_string(),
                    old_path: Some("old.txt".to_string()),
                    status: FileStatusKind::Renamed,
                },
            ]
        );
    }

    #[test]
    fn restore_staged_added_file_removes_it_from_index_and_worktree() {
        let repo = init_temp_repo("restore_staged_added_file");
        commit_initial_file(&repo.path);
        fs::write(repo.path.join("new.txt"), "new\n").expect("added file should be written");
        run_git_test(&repo.path, ["add", "new.txt"]);

        let status = status_for_repo(&repo.path).unwrap();
        assert_eq!(status.files[0].path, "new.txt");
        assert_eq!(status.files[0].staged, Some(FileStatusKind::Added));

        restore_staged_files(&repo.path, &status.files, &["new.txt".to_string()]).unwrap();

        let next_status = status_for_repo(&repo.path).unwrap();
        assert!(next_status.clean, "{:?}", next_status.files);
        assert!(!repo.path.join("new.txt").exists());
    }

    #[test]
    fn restore_staged_rename_restores_old_path_and_removes_new_path() {
        let repo = init_temp_repo("restore_staged_rename");
        commit_initial_file(&repo.path);
        run_git_test(&repo.path, ["mv", "old.txt", "new.txt"]);

        let status = status_for_repo(&repo.path).unwrap();
        assert_eq!(status.files[0].path, "new.txt");
        assert_eq!(status.files[0].old_path.as_deref(), Some("old.txt"));
        assert_eq!(status.files[0].staged, Some(FileStatusKind::Renamed));

        restore_staged_files(&repo.path, &status.files, &["new.txt".to_string()]).unwrap();

        let next_status = status_for_repo(&repo.path).unwrap();
        assert!(next_status.clean, "{:?}", next_status.files);
        assert!(repo.path.join("old.txt").exists());
        assert!(!repo.path.join("new.txt").exists());
    }

    #[test]
    fn plans_remote_branch_checkout_as_tracking_branch() {
        let repo = init_temp_repo("remote_checkout_plan");
        commit_initial_file(&repo.path);
        run_git_test(
            &repo.path,
            ["update-ref", "refs/remotes/origin/feature/demo", "HEAD"],
        );

        let plan = checkout_plan(&repo.path, "origin/feature/demo").unwrap();

        assert_eq!(
            plan,
            CheckoutPlan::TrackRemote {
                local: "feature/demo".to_string(),
                remote: "origin/feature/demo".to_string(),
            }
        );
    }

    #[test]
    fn remote_checkout_prefers_existing_local_branch() {
        let repo = init_temp_repo("remote_checkout_existing_local");
        commit_initial_file(&repo.path);
        run_git_test(&repo.path, ["branch", "feature/demo"]);
        run_git_test(
            &repo.path,
            ["update-ref", "refs/remotes/origin/feature/demo", "HEAD"],
        );

        let plan = checkout_plan(&repo.path, "origin/feature/demo").unwrap();

        assert_eq!(plan, CheckoutPlan::Local("feature/demo".to_string()));
    }

    #[test]
    fn restore_to_commit_resets_branch_to_selected_commit() {
        let repo = init_temp_repo("restore_to_commit");
        commit_initial_file(&repo.path);
        let first_commit = git_output_test(&repo.path, ["rev-parse", "HEAD"]);

        fs::write(repo.path.join("old.txt"), "second\n").expect("second file should be written");
        run_git_test(&repo.path, ["add", "old.txt"]);
        run_git_test(&repo.path, ["commit", "-q", "-m", "second"]);

        let status = restore_to_commit(
            repo.path.to_string_lossy().to_string(),
            first_commit.clone(),
        )
        .unwrap();
        let current_commit = git_output_test(&repo.path, ["rev-parse", "HEAD"]);
        let contents = fs::read_to_string(repo.path.join("old.txt")).unwrap();

        assert_eq!(current_commit, first_commit);
        assert_eq!(contents.replace("\r\n", "\n"), "original\n");
        assert!(status.clean, "{:?}", status.files);
    }

    #[test]
    fn restore_file_from_commit_restores_only_selected_file_to_worktree() {
        let repo = init_temp_repo("restore_file_from_commit");
        commit_initial_file(&repo.path);
        let first_commit = git_output_test(&repo.path, ["rev-parse", "HEAD"]);

        fs::write(repo.path.join("old.txt"), "second\n").expect("tracked file should be changed");
        fs::write(repo.path.join("other.txt"), "other\n").expect("other file should be written");
        run_git_test(&repo.path, ["add", "old.txt", "other.txt"]);
        run_git_test(&repo.path, ["commit", "-q", "-m", "second"]);

        fs::write(repo.path.join("old.txt"), "working\n").expect("working file should change");
        fs::write(repo.path.join("other.txt"), "working other\n")
            .expect("other working file should change");

        let status = restore_file_from_commit(
            repo.path.to_string_lossy().to_string(),
            first_commit,
            "old.txt".to_string(),
        )
        .unwrap();
        let old_contents = fs::read_to_string(repo.path.join("old.txt")).unwrap();
        let other_contents = fs::read_to_string(repo.path.join("other.txt")).unwrap();

        assert_eq!(old_contents.replace("\r\n", "\n"), "original\n");
        assert_eq!(other_contents.replace("\r\n", "\n"), "working other\n");
        assert!(status.files.iter().any(|file| file.path == "old.txt"));
    }

    #[test]
    fn restore_file_from_commit_can_restore_a_folder_path() {
        let repo = init_temp_repo("restore_folder_from_commit");
        fs::create_dir_all(repo.path.join("src")).expect("src directory should be created");
        fs::create_dir_all(repo.path.join("docs")).expect("docs directory should be created");
        fs::write(repo.path.join("src/a.txt"), "a1\n").expect("src a should be written");
        fs::write(repo.path.join("src/b.txt"), "b1\n").expect("src b should be written");
        fs::write(repo.path.join("docs/readme.txt"), "docs1\n").expect("docs should be written");
        run_git_test(&repo.path, ["add", "."]);
        run_git_test(&repo.path, ["commit", "-q", "-m", "initial tree"]);
        let first_commit = git_output_test(&repo.path, ["rev-parse", "HEAD"]);

        fs::write(repo.path.join("src/a.txt"), "a2\n").expect("src a should change");
        fs::write(repo.path.join("src/b.txt"), "b2\n").expect("src b should change");
        fs::write(repo.path.join("docs/readme.txt"), "docs2\n").expect("docs should change");

        restore_file_from_commit(
            repo.path.to_string_lossy().to_string(),
            first_commit,
            "src".to_string(),
        )
        .unwrap();

        let src_a = fs::read_to_string(repo.path.join("src/a.txt")).unwrap();
        let src_b = fs::read_to_string(repo.path.join("src/b.txt")).unwrap();
        let docs = fs::read_to_string(repo.path.join("docs/readme.txt")).unwrap();

        assert_eq!(src_a.replace("\r\n", "\n"), "a1\n");
        assert_eq!(src_b.replace("\r\n", "\n"), "b1\n");
        assert_eq!(docs.replace("\r\n", "\n"), "docs2\n");
    }

    #[test]
    fn repository_files_include_tracked_deleted_and_untracked_entries() {
        let repo = init_temp_repo("repository_files");
        commit_initial_file(&repo.path);
        fs::remove_file(repo.path.join("old.txt")).expect("tracked file should be deleted");
        fs::write(repo.path.join("new.txt"), "new\n").expect("untracked file should be written");

        let files = repository_files(&repo.path).unwrap();

        assert!(files.iter().any(|file| {
            file.path == "old.txt" && file.tracked && file.status == Some(FileStatusKind::Deleted)
        }));
        assert!(files.iter().any(|file| {
            file.path == "new.txt"
                && !file.tracked
                && file.status == Some(FileStatusKind::Untracked)
        }));
    }

    #[test]
    fn list_file_history_returns_commits_for_selected_file() {
        let repo = init_temp_repo("file_history");
        commit_initial_file(&repo.path);
        fs::write(repo.path.join("old.txt"), "second\n").expect("tracked file should change");
        run_git_test(&repo.path, ["add", "old.txt"]);
        run_git_test(&repo.path, ["commit", "-q", "-m", "touch selected"]);
        fs::write(repo.path.join("other.txt"), "other\n").expect("other file should be written");
        run_git_test(&repo.path, ["add", "other.txt"]);
        run_git_test(&repo.path, ["commit", "-q", "-m", "touch other"]);

        let commits = list_file_history(
            repo.path.to_string_lossy().to_string(),
            "old.txt".to_string(),
            Some(10),
        )
        .unwrap();

        assert_eq!(commits.len(), 2);
        assert_eq!(commits[0].summary, "touch selected");
        assert_eq!(commits[1].summary, "init");
    }

    #[test]
    fn list_file_history_returns_commits_for_selected_folder() {
        let repo = init_temp_repo("folder_history");
        fs::create_dir_all(repo.path.join("src")).expect("src directory should be created");
        fs::create_dir_all(repo.path.join("docs")).expect("docs directory should be created");
        fs::write(repo.path.join("src/a.txt"), "a1\n").expect("src file should be written");
        run_git_test(&repo.path, ["add", "."]);
        run_git_test(&repo.path, ["commit", "-q", "-m", "src initial"]);
        fs::write(repo.path.join("docs/readme.txt"), "docs\n")
            .expect("docs file should be written");
        run_git_test(&repo.path, ["add", "."]);
        run_git_test(&repo.path, ["commit", "-q", "-m", "docs only"]);
        fs::write(repo.path.join("src/a.txt"), "a2\n").expect("src file should change");
        run_git_test(&repo.path, ["add", "."]);
        run_git_test(&repo.path, ["commit", "-q", "-m", "src update"]);

        let commits = list_file_history(
            repo.path.to_string_lossy().to_string(),
            "src".to_string(),
            Some(10),
        )
        .unwrap();

        assert_eq!(commits.len(), 2);
        assert_eq!(commits[0].summary, "src update");
        assert_eq!(commits[1].summary, "src initial");
    }
}