use super::*;

#[derive(Debug, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct ReviewMergeOptions {
    methods: Vec<String>,
    default_method: String,
}

fn merge_options(provider: &str, repository: &serde_json::Value) -> Result<ReviewMergeOptions, String> {
    let candidates: &[(&str, &str)] = match provider {
        "gitea" => &[("merge", "allow_merge_commits"), ("rebase", "allow_rebase"), ("rebase-merge", "allow_rebase_explicit"), ("squash", "allow_squash_merge"), ("fast-forward-only", "allow_fast_forward_only_merge")],
        "github" => &[("merge", "allow_merge_commit"), ("squash", "allow_squash_merge"), ("rebase", "allow_rebase_merge")],
        "azure-devops" => &[("merge", ""), ("squash", ""), ("rebase", ""), ("rebase-merge", "")],
        "gitlab" | "gitlab-self-hosted" => &[],
        _ => return Err("Unsupported integration provider.".into()),
    };
    let mut methods: Vec<String> = candidates.iter()
        .filter(|(_, field)| field.is_empty() || repository.get(*field).and_then(serde_json::Value::as_bool) == Some(true))
        .map(|(method, _)| method.to_string()).collect();
    let preferred = if provider.starts_with("gitlab") {
        match repository.get("squash_option").and_then(serde_json::Value::as_str) {
            Some("always") => { methods.push("squash".into()); "squash" },
            Some("never") => { methods.push("merge".into()); "merge" },
            Some("default_on") => { methods.extend(["merge".into(), "squash".into()]); "squash" },
            Some("default_off") => { methods.extend(["merge".into(), "squash".into()]); "merge" },
            // Older servers may not expose squash settings; leave the server's default intact.
            _ => { methods.push("default".into()); "default" },
        }
    } else {
        repository.get("default_merge_style").and_then(serde_json::Value::as_str).unwrap_or("merge")
    };
    let default_method = methods.iter().find(|method| method.as_str() == preferred)
        .or_else(|| methods.first()).cloned().unwrap_or_default();
    Ok(ReviewMergeOptions { methods, default_method })
}

pub(super) fn merge_payload(provider: &str, method: Option<&str>) -> Result<serde_json::Value, String> {
    let method = method.unwrap_or("default");
    match (provider, method) {
        ("github", "default") | ("gitlab" | "gitlab-self-hosted" | "azure-devops", "default") => Ok(serde_json::json!({})),
        ("github", "merge" | "squash" | "rebase") => Ok(serde_json::json!({ "merge_method": method })),
        ("gitea", "default") => Ok(serde_json::json!({ "Do": "merge" })),
        ("gitea", "merge" | "squash" | "rebase" | "rebase-merge" | "fast-forward-only") => Ok(serde_json::json!({ "Do": method })),
        ("gitlab" | "gitlab-self-hosted", "merge" | "squash") => Ok(serde_json::json!({ "squash": method == "squash" })),
        ("azure-devops", "merge" | "squash" | "rebase" | "rebase-merge") => {
            let strategy = match method { "merge" => "noFastForward", "rebase-merge" => "rebaseMerge", other => other };
            Ok(serde_json::json!({ "completionOptions": { "mergeStrategy": strategy } }))
        },
        _ => Err("Unsupported merge method for this integration provider.".into()),
    }
}

#[tauri::command]
pub async fn get_integration_review_merge_options(provider: String, base_url: String, token: String, repository_id: String, repository_name: String) -> Result<ReviewMergeOptions, String> {
    tokio::time::timeout(REVIEW_REQUEST_TIMEOUT, tauri::async_runtime::spawn_blocking(move || {
        if token.trim().is_empty() { return Err("No token is stored for this integration.".into()); }
        let base = normalized_base_url(&base_url)?;
        if provider == "azure-devops" { return merge_options(&provider, &serde_json::json!({})); }
        let client = client()?;
        let request = match provider.as_str() {
            "github" | "gitea" => {
                if repository_name.split('/').count() != 2 { return Err("Invalid repository name.".into()); }
                if provider == "github" {
                    client.get(format!("{}/repos/{repository_name}", github_api_base_url(&base)?))
                        .bearer_auth(&token).header(ACCEPT, "application/vnd.github+json")
                } else {
                    client.get(format!("{base}/api/v1/repos/{repository_name}"))
                        .header("Authorization", format!("token {token}"))
                }
            },
            "gitlab" | "gitlab-self-hosted" => {
                if repository_id.is_empty() { return Err("Invalid project identifier.".into()); }
                client.get(format!("{base}/api/v4/projects/{repository_id}")).header("PRIVATE-TOKEN", &token)
            },
            _ => return Err("Unsupported integration provider.".into()),
        };
        let response = request.header(USER_AGENT, "Gitty").send().map_err(|err| format!("Could not load merge options: {err}"))?;
        if !response.status().is_success() { return Err(response_error(response, &provider)); }
        let repository = response.json::<serde_json::Value>().map_err(|err| format!("Could not read merge options: {err}"))?;
        merge_options(&provider, &repository)
    })).await.map_err(|_| "The integration API did not respond within 35 seconds.".to_string())?
        .map_err(|err| format!("Could not load merge options: {err}"))?
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn repository_settings_filter_methods_and_select_allowed_default() {
        let options = merge_options("gitea", &serde_json::json!({"allow_merge_commits":false,"allow_rebase":true,"allow_rebase_explicit":true,"allow_squash_merge":true,"default_merge_style":"squash"})).unwrap();
        assert_eq!(options.methods, ["rebase", "rebase-merge", "squash"]);
        assert_eq!(options.default_method, "squash");
        let options = merge_options("github", &serde_json::json!({"allow_squash_merge":true})).unwrap();
        assert_eq!(options.methods, ["squash"]);
        assert_eq!(options.default_method, "squash");
        assert!(merge_options("gitea", &serde_json::json!({})).unwrap().methods.is_empty());
    }
    #[test]
    fn gitlab_respects_required_and_forbidden_squashing() {
        for (setting, expected) in [("always", "squash"), ("never", "merge"), ("default_on", "squash"), ("default_off", "merge")] {
            let options = merge_options("gitlab", &serde_json::json!({"squash_option":setting})).unwrap();
            assert_eq!(options.default_method, expected);
            assert_eq!(options.methods.len(), if setting.starts_with("default") { 2 } else { 1 });
        }
    }
    #[test]
    fn payloads_use_provider_specific_methods_and_reject_invalid_choices() {
        for method in ["merge", "rebase", "rebase-merge", "squash", "fast-forward-only"] {
            assert_eq!(merge_payload("gitea", Some(method)).unwrap()["Do"], method);
        }
        assert_eq!(merge_payload("github", Some("rebase")).unwrap()["merge_method"], "rebase");
        assert_eq!(merge_payload("azure-devops", Some("rebase-merge")).unwrap()["completionOptions"]["mergeStrategy"], "rebaseMerge");
        assert_eq!(merge_payload("azure-devops", Some("merge")).unwrap()["completionOptions"]["mergeStrategy"], "noFastForward");
        assert_eq!(merge_payload("gitlab", Some("squash")).unwrap()["squash"], true);
        assert_eq!(merge_payload("gitlab", Some("merge")).unwrap()["squash"], false);
        assert!(merge_payload("github", Some("fast-forward-only")).is_err());
        assert!(merge_payload("gitlab", Some("rebase")).is_err());
        assert!(merge_payload("gitea", Some("manually-merged")).is_err());
    }
}