use crate::config::ProjectConfig;
use std::path::{Path, PathBuf};
use std::process::Command;

/// Write a `.mcp.json` file in the given directory pointing to the MCP server
/// at the given port.
pub fn write_mcp_json(dir: &Path, port: u16) -> Result<(), String> {
    let content = format!(
        "{{\n  \"mcpServers\": {{\n    \"story-kit\": {{\n      \"type\": \"http\",\n      \"url\": \"http://localhost:{port}/mcp\"\n    }}\n  }}\n}}\n"
    );
    std::fs::write(dir.join(".mcp.json"), content).map_err(|e| format!("Write .mcp.json: {e}"))
}

#[derive(Debug, Clone)]
#[allow(dead_code)]
pub struct WorktreeInfo {
    pub path: PathBuf,
    pub branch: String,
    pub base_branch: String,
}

/// Worktree path as a sibling of the project root: `{project_root}-story-{id}`.
/// E.g. `/path/to/story-kit-app` → `/path/to/story-kit-app-story-42_foo`.
fn worktree_path(project_root: &Path, story_id: &str) -> PathBuf {
    let parent = project_root.parent().unwrap_or(project_root);
    let dir_name = project_root
        .file_name()
        .map(|n| n.to_string_lossy().to_string())
        .unwrap_or_else(|| "project".to_string());
    parent.join(format!("{dir_name}-story-{story_id}"))
}

fn branch_name(story_id: &str) -> String {
    format!("feature/story-{story_id}")
}

/// Detect the current branch of the project root (the base branch worktrees fork from).
fn detect_base_branch(project_root: &Path) -> String {
    Command::new("git")
        .args(["rev-parse", "--abbrev-ref", "HEAD"])
        .current_dir(project_root)
        .output()
        .ok()
        .and_then(|o| {
            if o.status.success() {
                Some(String::from_utf8_lossy(&o.stdout).trim().to_string())
            } else {
                None
            }
        })
        .unwrap_or_else(|| "master".to_string())
}

/// Create a git worktree for the given story.
///
/// - Creates the worktree at `{project_root}-story-{story_id}` (sibling directory)
///   on branch `feature/story-{story_id}`.
/// - Writes `.mcp.json` in the worktree pointing to the MCP server at `port`.
/// - Runs setup commands from the config for each component.
/// - If the worktree/branch already exists, reuses rather than errors.
pub async fn create_worktree(
    project_root: &Path,
    story_id: &str,
    config: &ProjectConfig,
    port: u16,
) -> Result<WorktreeInfo, String> {
    let wt_path = worktree_path(project_root, story_id);
    let branch = branch_name(story_id);
    let base_branch = detect_base_branch(project_root);
    let root = project_root.to_path_buf();

    // Already exists — reuse
    if wt_path.exists() {
        write_mcp_json(&wt_path, port)?;
        run_setup_commands(&wt_path, config).await?;
        return Ok(WorktreeInfo {
            path: wt_path,
            branch,
            base_branch,
        });
    }

    let wt = wt_path.clone();
    let br = branch.clone();

    tokio::task::spawn_blocking(move || create_worktree_sync(&root, &wt, &br))
        .await
        .map_err(|e| format!("spawn_blocking: {e}"))??;

    write_mcp_json(&wt_path, port)?;
    run_setup_commands(&wt_path, config).await?;

    Ok(WorktreeInfo {
        path: wt_path,
        branch,
        base_branch,
    })
}

fn create_worktree_sync(
    project_root: &Path,
    wt_path: &Path,
    branch: &str,
) -> Result<(), String> {
    // Ensure the parent directory exists
    if let Some(parent) = wt_path.parent() {
        std::fs::create_dir_all(parent)
            .map_err(|e| format!("Create worktree dir: {e}"))?;
    }

    // Prune stale worktree references (e.g. directories deleted externally)
    let _ = Command::new("git")
        .args(["worktree", "prune"])
        .current_dir(project_root)
        .output();

    // Try to create branch. If it already exists that's fine.
    let _ = Command::new("git")
        .args(["branch", branch])
        .current_dir(project_root)
        .output();

    // Create worktree
    let output = Command::new("git")
        .args([
            "worktree",
            "add",
            &wt_path.to_string_lossy(),
            branch,
        ])
        .current_dir(project_root)
        .output()
        .map_err(|e| format!("git worktree add: {e}"))?;

    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        // If it says already checked out, that's fine
        if stderr.contains("already checked out") || stderr.contains("already exists") {
            return Ok(());
        }
        return Err(format!("git worktree add failed: {stderr}"));
    }

    Ok(())
}

/// Remove a git worktree and its branch.
#[allow(dead_code)]
pub async fn remove_worktree(
    project_root: &Path,
    info: &WorktreeInfo,
    config: &ProjectConfig,
) -> Result<(), String> {
    run_teardown_commands(&info.path, config).await?;

    let root = project_root.to_path_buf();
    let wt_path = info.path.clone();
    let branch = info.branch.clone();

    tokio::task::spawn_blocking(move || remove_worktree_sync(&root, &wt_path, &branch))
        .await
        .map_err(|e| format!("spawn_blocking: {e}"))?
}

#[allow(dead_code)]
fn remove_worktree_sync(
    project_root: &Path,
    wt_path: &Path,
    branch: &str,
) -> Result<(), String> {
    // Remove worktree
    let output = Command::new("git")
        .args([
            "worktree",
            "remove",
            "--force",
            &wt_path.to_string_lossy(),
        ])
        .current_dir(project_root)
        .output()
        .map_err(|e| format!("git worktree remove: {e}"))?;

    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        eprintln!("[worktree] remove warning: {stderr}");
    }

    // Delete branch (best effort)
    let _ = Command::new("git")
        .args(["branch", "-d", branch])
        .current_dir(project_root)
        .output();

    Ok(())
}

async fn run_setup_commands(wt_path: &Path, config: &ProjectConfig) -> Result<(), String> {
    for component in &config.component {
        let cmd_dir = wt_path.join(&component.path);
        for cmd in &component.setup {
            run_shell_command(cmd, &cmd_dir).await?;
        }
    }
    Ok(())
}

#[allow(dead_code)]
async fn run_teardown_commands(wt_path: &Path, config: &ProjectConfig) -> Result<(), String> {
    for component in &config.component {
        let cmd_dir = wt_path.join(&component.path);
        for cmd in &component.teardown {
            // Best effort — don't fail teardown
            if let Err(e) = run_shell_command(cmd, &cmd_dir).await {
                eprintln!("[worktree] teardown warning for {}: {e}", component.name);
            }
        }
    }
    Ok(())
}

async fn run_shell_command(cmd: &str, cwd: &Path) -> Result<(), String> {
    let cmd = cmd.to_string();
    let cwd = cwd.to_path_buf();

    tokio::task::spawn_blocking(move || {
        eprintln!("[worktree] Running: {cmd} in {}", cwd.display());
        let output = Command::new("sh")
            .args(["-c", &cmd])
            .current_dir(&cwd)
            .output()
            .map_err(|e| format!("Run '{cmd}': {e}"))?;

        if !output.status.success() {
            let stderr = String::from_utf8_lossy(&output.stderr);
            return Err(format!("Command '{cmd}' failed: {stderr}"));
        }
        Ok(())
    })
    .await
    .map_err(|e| format!("spawn_blocking: {e}"))?
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs;
    use tempfile::TempDir;

    /// Initialise a bare-minimum git repo so worktree operations work.
    fn init_git_repo(dir: &Path) {
        Command::new("git")
            .args(["init"])
            .current_dir(dir)
            .output()
            .expect("git init");
        Command::new("git")
            .args(["commit", "--allow-empty", "-m", "init"])
            .current_dir(dir)
            .output()
            .expect("git commit");
    }

    #[test]
    fn write_mcp_json_uses_given_port() {
        let tmp = TempDir::new().unwrap();
        write_mcp_json(tmp.path(), 4242).unwrap();
        let content = std::fs::read_to_string(tmp.path().join(".mcp.json")).unwrap();
        assert!(content.contains("http://localhost:4242/mcp"));
    }

    #[test]
    fn write_mcp_json_default_port() {
        let tmp = TempDir::new().unwrap();
        write_mcp_json(tmp.path(), 3001).unwrap();
        let content = std::fs::read_to_string(tmp.path().join(".mcp.json")).unwrap();
        assert!(content.contains("http://localhost:3001/mcp"));
    }

    #[test]
    fn create_worktree_after_stale_reference() {
        let tmp = TempDir::new().unwrap();
        let project_root = tmp.path().join("my-project");
        fs::create_dir_all(&project_root).unwrap();
        init_git_repo(&project_root);

        let wt_path = tmp.path().join("my-worktree");
        let branch = "feature/test-stale";

        // First creation should succeed
        create_worktree_sync(&project_root, &wt_path, branch).unwrap();
        assert!(wt_path.exists());

        // Simulate external deletion (e.g., rm -rf by another agent)
        fs::remove_dir_all(&wt_path).unwrap();
        assert!(!wt_path.exists());

        // Second creation should succeed despite stale git reference.
        // Without `git worktree prune`, this fails with "already checked out"
        // or "already exists".
        let result = create_worktree_sync(&project_root, &wt_path, branch);
        assert!(
            result.is_ok(),
            "Expected worktree creation to succeed after stale reference, got: {:?}",
            result.err()
        );
        assert!(wt_path.exists());
    }
}