use super::*;
use crate::git::review_cleanup::{self, CleanupPlan};

struct ReviewHead {
    source: String,
    target: String,
    sha: String,
    merged: bool,
    urls: Vec<String>,
}

fn read_payload(
    client: &Client,
    base: &str,
    username: &str,
    token: &str,
    provider: &str,
    repository_id: &str,
    repository_name: &str,
    number: u64,
) -> Result<serde_json::Value, String> {
    let request = match provider {
        "github" => client
            .get(format!(
                "{}/repos/{repository_name}/pulls/{number}",
                github_api_base_url(base)?
            ))
            .bearer_auth(token)
            .header(ACCEPT, "application/vnd.github+json"),
        "gitea" => client
            .get(format!(
                "{base}/api/v1/repos/{repository_name}/pulls/{number}"
            ))
            .header("Authorization", format!("token {token}")),
        "gitlab" | "gitlab-self-hosted" => client
            .get(format!(
                "{base}/api/v4/projects/{repository_id}/merge_requests/{number}"
            ))
            .header("PRIVATE-TOKEN", token),
        "azure-devops" => client
            .get(azure_review_endpoint(
                base,
                repository_name,
                repository_id,
                number,
            )?)
            .basic_auth(
                if username.is_empty() {
                    "gitty"
                } else {
                    username
                },
                Some(token),
            ),
        _ => return Err("Unsupported integration provider.".into()),
    };
    let response = request
        .header(USER_AGENT, "Gitty")
        .send()
        .map_err(|err| format!("Could not verify PR cleanup: {err}"))?;
    if !response.status().is_success() {
        return Err(response_error(response, provider));
    }
    response
        .json()
        .map_err(|err| format!("Could not read PR cleanup details: {err}"))
}

fn review_head(provider: &str, payload: &serde_json::Value) -> Result<ReviewHead, String> {
    let (source, target, sha, merged, repository) = match provider {
        "github" | "gitea" => {
            let head_id = payload.pointer("/head/repo/id").filter(|id| !id.is_null());
            let base_id = payload.pointer("/base/repo/id").filter(|id| !id.is_null());
            if head_id.is_none() || head_id != base_id {
                return Err("Automatic local and remote cleanup is only supported for PRs within the same repository. Disable cleanup for this fork PR.".into());
            }
            (
                value_string(payload, &["head", "ref"]),
                value_string(payload, &["base", "ref"]),
                value_string(payload, &["head", "sha"]),
                payload.get("merged").and_then(serde_json::Value::as_bool) == Some(true),
                &payload["base"]["repo"],
            )
        }
        "gitlab" | "gitlab-self-hosted" => {
            let source_id = payload.get("source_project_id").filter(|id| !id.is_null());
            if source_id.is_none() || source_id != payload.get("target_project_id") {
                return Err("Automatic cleanup is only supported for merge requests within the same project. Disable cleanup for this fork MR.".into());
            }
            (
                value_string(payload, &["source_branch"]),
                value_string(payload, &["target_branch"]),
                value_string(payload, &["sha"]),
                value_string(payload, &["state"]) == "merged",
                &payload["gitty_repository"],
            )
        }
        "azure-devops" => {
            if payload
                .get("forkSource")
                .is_some_and(|fork| !fork.is_null())
            {
                return Err(
                    "Automatic cleanup is not supported for fork PRs. Disable cleanup for this PR."
                        .into(),
                );
            }
            (
                value_string(payload, &["sourceRefName"])
                    .trim_start_matches("refs/heads/")
                    .into(),
                value_string(payload, &["targetRefName"])
                    .trim_start_matches("refs/heads/")
                    .into(),
                value_string(payload, &["lastMergeSourceCommit", "commitId"]),
                value_string(payload, &["status"]) == "completed",
                &payload["repository"],
            )
        }
        _ => return Err("Unsupported integration provider.".into()),
    };
    let default_branch = value_string(
        repository,
        &[if provider == "azure-devops" {
            "defaultBranch"
        } else {
            "default_branch"
        }],
    );
    if !source.is_empty() && source == default_branch.trim_start_matches("refs/heads/") {
        return Err("The repository's default branch cannot be deleted by PR cleanup.".into());
    }
    let urls = [
        "clone_url",
        "ssh_url",
        "http_url_to_repo",
        "ssh_url_to_repo",
        "remoteUrl",
        "sshUrl",
    ]
    .iter()
    .filter_map(|key| {
        repository
            .get(key)
            .and_then(serde_json::Value::as_str)
            .filter(|url| !url.is_empty())
            .map(str::to_string)
    })
    .collect();
    Ok(ReviewHead {
        source,
        target,
        sha,
        merged,
        urls,
    })
}

pub(super) struct PreparedCleanup {
    plan: CleanupPlan,
    source: String,
    target: String,
    sha: String,
}

pub(super) fn prepare(
    client: &Client,
    base: &str,
    username: &str,
    token: &str,
    provider: &str,
    repository_id: &str,
    repository_name: &str,
    number: u64,
    path: &str,
) -> Result<PreparedCleanup, String> {
    let mut payload = read_payload(
        client,
        base,
        username,
        token,
        provider,
        repository_id,
        repository_name,
        number,
    )?;
    if provider.starts_with("gitlab") {
        let response = client
            .get(format!("{base}/api/v4/projects/{repository_id}"))
            .header(USER_AGENT, "Gitty")
            .header("PRIVATE-TOKEN", token)
            .send()
            .map_err(|err| err.to_string())?;
        if !response.status().is_success() {
            return Err(response_error(response, "GitLab"));
        }
        payload["gitty_repository"] = response.json().map_err(|err| err.to_string())?;
    }
    let head = review_head(provider, &payload)?;
    if head.merged {
        return Err("This PR is already merged. Refresh the review list.".into());
    }
    let plan = review_cleanup::prepare(
        path,
        &head.source,
        &head.target,
        &head.sha,
        &head.urls,
        username,
        token,
    )?;
    Ok(PreparedCleanup {
        plan,
        source: head.source,
        target: head.target,
        sha: head.sha,
    })
}

pub(super) fn finish(
    prepared: &PreparedCleanup,
    client: &Client,
    base: &str,
    username: &str,
    token: &str,
    provider: &str,
    repository_id: &str,
    repository_name: &str,
    number: u64,
) -> Result<(), String> {
    // Providers may accept a merge asynchronously. Never delete a branch on acceptance alone.
    for attempt in 0..10 {
        let payload = read_payload(
            client,
            base,
            username,
            token,
            provider,
            repository_id,
            repository_name,
            number,
        )?;
        let head = review_head(provider, &payload)?;
        if head.source != prepared.source
            || head.target != prepared.target
            || head.sha != prepared.sha
        {
            return Err(
                "The PR branches or source commit changed during merging. Branches were preserved."
                    .into(),
            );
        }
        if head.merged {
            return review_cleanup::finish(&prepared.plan, username, token);
        }
        if attempt < 9 {
            std::thread::sleep(Duration::from_millis(500));
        }
    }
    Err("The provider has not confirmed that the merge completed. No branches were deleted.".into())
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn cleanup_rejects_forks_and_default_branch_and_reads_merge_confirmation() {
        let mut payload = serde_json::json!({"head":{"ref":"feature","sha":"abc","repo":{"id":1}},"base":{"ref":"release","repo":{"id":1,"default_branch":"main","clone_url":"https://git.test/team/app.git"}},"merged":true});
        let head = review_head("gitea", &payload).unwrap();
        assert!(head.merged);
        assert_eq!(head.target, "release");
        assert_eq!(head.urls, ["https://git.test/team/app.git"]);
        payload["head"]["repo"]["id"] = serde_json::json!(2);
        assert!(review_head("gitea", &payload).is_err());
        payload["head"]["repo"]["id"] = serde_json::json!(1);
        payload["head"]["ref"] = serde_json::json!("main");
        assert!(review_head("github", &payload).is_err());
    }
}