use std::path::Path;
use std::process::Command;

use crate::io::story_metadata::clear_front_matter_field_in_content;
use crate::slog;

type ContentTransform = Option<Box<dyn Fn(&str) -> String>>;

pub(super) fn item_type_from_id(item_id: &str) -> &'static str {
    // New format: {digits}_{type}_{slug}
    let after_num = item_id.trim_start_matches(|c: char| c.is_ascii_digit());
    if after_num.starts_with("_bug_") {
        "bug"
    } else if after_num.starts_with("_spike_") {
        "spike"
    } else {
        "story"
    }
}

/// Move a work item to a new pipeline stage via the database.
///
/// Looks up the item in the CRDT to verify it exists in one of the expected
/// `sources` stages, then updates the stage.  Optionally clears front-matter
/// fields from the stored content.  Returns the source stage on success.
fn move_item<'a>(
    project_root: &Path,
    story_id: &str,
    sources: &'a [&'a str],
    target_dir: &str,
    extra_done_dirs: &[&str],
    missing_ok: bool,
    fields_to_clear: &[&str],
) -> Result<Option<&'a str>, String> {
    // Check if the item is already in the target stage or a done stage.
    // Use the typed projection for compile-safe stage comparison.
    if let Ok(Some(typed_item)) = crate::pipeline_state::read_typed(story_id) {
        let current_dir = typed_item.stage.dir_name();
        if current_dir == target_dir
            || extra_done_dirs.contains(&current_dir)
        {
            return Ok(None); // Idempotent: already there.
        }

        // Verify it's in one of the expected source stages.
        let src_dir = sources.iter().find(|&&s| current_dir == s).copied();
        if src_dir.is_none() && !missing_ok {
            let locs = sources
                .iter()
                .map(|s| format!("work/{s}/"))
                .collect::<Vec<_>>()
                .join(" or ");
            return Err(format!("Work item '{story_id}' not found in {locs}."));
        }
        let src_dir = src_dir.unwrap_or(sources[0]);

        // Optionally clear front-matter fields from the stored content.
        let transform: ContentTransform = if fields_to_clear.is_empty() {
            None
        } else {
            let fields: Vec<String> = fields_to_clear.iter().map(|s| s.to_string()).collect();
            Some(Box::new(move |content: &str| {
                let mut result = content.to_string();
                for field in &fields {
                    result = clear_front_matter_field_in_content(&result, field);
                }
                result
            }))
        };

        crate::db::move_item_stage(
            story_id,
            target_dir,
            transform.as_ref().map(|f| f.as_ref()),
        );

        slog!("[lifecycle] Moved '{story_id}' from work/{src_dir}/ to work/{target_dir}/");
        return Ok(Some(src_dir));
    }

    // Item not found in CRDT — check the content store as fallback.
    if crate::db::read_content(story_id).is_some() {
        // Content exists but not in CRDT yet — write it through.
        let content = crate::db::read_content(story_id).unwrap();
        crate::db::write_item_with_content(story_id, target_dir, &content);
        slog!("[lifecycle] Moved '{story_id}' to work/{target_dir}/ (content store fallback)");
        return Ok(Some(sources[0]));
    }

    // Try filesystem fallback for backwards compatibility during migration.
    {
        let sk = project_root.join(".huskies").join("work");
        if let Some((src_dir, src_path)) = sources.iter().find_map(|&s| {
            let p = sk.join(s).join(format!("{story_id}.md"));
            p.exists().then_some((s, p))
        }) && let Ok(mut content) = std::fs::read_to_string(&src_path) {
                // Optionally clear front-matter fields.
                for field in fields_to_clear {
                    content = clear_front_matter_field_in_content(&content, field);
                }
                // Import to DB.
                crate::db::write_item_with_content(story_id, target_dir, &content);
                // Also move on filesystem for backwards compat.
                let target_path = sk.join(target_dir).join(format!("{story_id}.md"));
                let _ = std::fs::create_dir_all(sk.join(target_dir));
                let _ = std::fs::write(&target_path, &content);
                // Only remove the source if it differs from the target (avoid
                // deleting the file when src and target are the same directory).
                if src_dir != target_dir {
                    let _ = std::fs::remove_file(&src_path);
                }
                slog!("[lifecycle] Moved '{story_id}' from work/{src_dir}/ to work/{target_dir}/");
                return Ok(Some(src_dir));
        }
    }

    if missing_ok {
        slog!("[lifecycle] Work item '{story_id}' not found; skipping move to work/{target_dir}/");
        return Ok(None);
    }

    let locs = sources
        .iter()
        .map(|s| format!("work/{s}/"))
        .collect::<Vec<_>>()
        .join(" or ");
    Err(format!("Work item '{story_id}' not found in {locs}."))
}

/// Move a work item (story, bug, or spike) from `work/1_backlog/` to `work/2_current/`.
///
/// Idempotent: if already in `2_current/`, returns Ok. If not found in `1_backlog/`, logs and returns Ok.
pub fn move_story_to_current(project_root: &Path, story_id: &str) -> Result<(), String> {
    move_item(project_root, story_id, &["1_backlog"], "2_current", &[], true, &[]).map(|_| ())
}

/// Check whether a feature branch `feature/story-{story_id}` exists and has
/// commits that are not yet on master.  Returns `true` when there is unmerged
/// work, `false` when there is no branch or all its commits are already
/// reachable from master.
pub fn feature_branch_has_unmerged_changes(project_root: &Path, story_id: &str) -> bool {
    let branch = format!("feature/story-{story_id}");

    // Check if the branch exists.
    let branch_check = Command::new("git")
        .args(["rev-parse", "--verify", &branch])
        .current_dir(project_root)
        .output();
    match branch_check {
        Ok(out) if out.status.success() => {}
        _ => return false, // No feature branch → nothing to merge.
    }

    // Check if the branch has commits not reachable from master.
    let log = Command::new("git")
        .args(["log", &format!("master..{branch}"), "--oneline"])
        .current_dir(project_root)
        .output();
    match log {
        Ok(out) => {
            let stdout = String::from_utf8_lossy(&out.stdout);
            !stdout.trim().is_empty()
        }
        Err(_) => false,
    }
}

/// Move a story from `work/2_current/` or `work/4_merge/` to `work/5_done/`.
///
/// Idempotent if already in `5_done/` or `6_archived/`. Errors if not found in `2_current/` or `4_merge/`.
pub fn move_story_to_done(project_root: &Path, story_id: &str) -> Result<(), String> {
    move_item(
        project_root,
        story_id,
        &["2_current", "4_merge"],
        "5_done",
        &["6_archived"],
        false,
        &["merge_failure", "retry_count", "blocked"],
    )
    .map(|_| ())
}

/// Move a story/bug from `work/2_current/` or `work/3_qa/` to `work/4_merge/`.
///
/// Idempotent if already in `4_merge/`. Errors if not found in `2_current/` or `3_qa/`.
pub fn move_story_to_merge(project_root: &Path, story_id: &str) -> Result<(), String> {
    move_item(
        project_root,
        story_id,
        &["2_current", "3_qa"],
        "4_merge",
        &[],
        false,
        &["retry_count", "blocked"],
    )
    .map(|_| ())
}

/// Move a story/bug from `work/2_current/` to `work/3_qa/`.
///
/// Idempotent if already in `3_qa/`. Errors if not found in `2_current/`.
pub fn move_story_to_qa(project_root: &Path, story_id: &str) -> Result<(), String> {
    move_item(
        project_root,
        story_id,
        &["2_current"],
        "3_qa",
        &[],
        false,
        &["retry_count", "blocked"],
    )
    .map(|_| ())
}

/// Move a story from `work/3_qa/` back to `work/2_current/`, clearing `review_hold` and writing notes.
pub fn reject_story_from_qa(project_root: &Path, story_id: &str, notes: &str) -> Result<(), String> {
    let moved = move_item(project_root, story_id, &["3_qa"], "2_current", &[], false, &["review_hold"])?;
    if moved.is_some() && !notes.is_empty() {
        // Append rejection notes to the stored content.
        if let Some(content) = crate::db::read_content(story_id) {
            let updated = crate::io::story_metadata::write_rejection_notes_to_content(&content, notes);
            crate::db::write_content(story_id, &updated);
            // Re-sync to DB.
            crate::db::write_item_with_content(story_id, "2_current", &updated);
        }
    }
    Ok(())
}

/// Move any work item to an arbitrary pipeline stage by searching all stages.
///
/// Accepts `target_stage` as one of: `backlog`, `current`, `qa`, `merge`, `done`.
/// Idempotent: if the item is already in the target stage, returns Ok.
/// Returns `(from_stage, to_stage)` on success.
pub fn move_story_to_stage(
    project_root: &Path,
    story_id: &str,
    target_stage: &str,
) -> Result<(String, String), String> {
    const STAGES: &[(&str, &str)] = &[
        ("backlog", "1_backlog"),
        ("current", "2_current"),
        ("qa", "3_qa"),
        ("merge", "4_merge"),
        ("done", "5_done"),
        ("archived", "6_archived"),
    ];

    let target_dir = STAGES
        .iter()
        .filter(|(name, _)| *name != "archived")
        .find(|(name, _)| *name == target_stage)
        .map(|(_, dir)| *dir)
        .ok_or_else(|| {
            format!(
                "Invalid target_stage '{target_stage}'. Must be one of: backlog, current, qa, merge, done"
            )
        })?;

    let all_dirs: Vec<&str> = STAGES.iter().map(|(_, dir)| *dir).collect();

    match move_item(project_root, story_id, &all_dirs, target_dir, &[], false, &[])
        .map_err(|_| format!("Work item '{story_id}' not found in any pipeline stage."))?
    {
        Some(src_dir) => {
            let from_stage = STAGES
                .iter()
                .find(|(_, dir)| *dir == src_dir)
                .map(|(name, _)| *name)
                .unwrap_or(src_dir);
            Ok((from_stage.to_string(), target_stage.to_string()))
        }
        None => Ok((target_stage.to_string(), target_stage.to_string())),
    }
}

/// Move a bug from `work/2_current/` or `work/1_backlog/` to `work/5_done/`.
///
/// Idempotent if already in `5_done/`. Errors if not found in `2_current/` or `1_backlog/`.
pub fn close_bug_to_archive(project_root: &Path, bug_id: &str) -> Result<(), String> {
    move_item(
        project_root,
        bug_id,
        &["2_current", "1_backlog"],
        "5_done",
        &[],
        false,
        &[],
    )
    .map(|_| ())
}

#[cfg(test)]
mod tests {
    use super::*;

    // ── move_story_to_current tests ────────────────────────────────────────────

    #[test]
    fn move_story_to_current_from_filesystem() {
        let tmp = tempfile::tempdir().unwrap();
        let backlog = tmp.path().join(".huskies/work/1_backlog");
        let current = tmp.path().join(".huskies/work/2_current");
        std::fs::create_dir_all(&backlog).unwrap();
        std::fs::create_dir_all(&current).unwrap();
        std::fs::write(
            backlog.join("10_story_foo.md"),
            "---\nname: Test\n---\n# Story\n",
        )
        .unwrap();

        move_story_to_current(tmp.path(), "10_story_foo").unwrap();

        // Verify the story was moved to current.
        assert!(
            current.join("10_story_foo.md").exists(),
            "story should be in 2_current/"
        );
        assert!(
            !backlog.join("10_story_foo.md").exists(),
            "story should not still be in 1_backlog/"
        );
    }

    #[test]
    fn move_story_to_current_noop_when_not_found() {
        let tmp = tempfile::tempdir().unwrap();
        assert!(move_story_to_current(tmp.path(), "99_missing").is_ok());
    }

    // ── item_type_from_id tests ────────────────────────────────────────────────

    #[test]
    fn item_type_from_id_detects_types() {
        assert_eq!(item_type_from_id("1_bug_test"), "bug");
        assert_eq!(item_type_from_id("1_spike_research"), "spike");
        assert_eq!(item_type_from_id("50_story_my_story"), "story");
        assert_eq!(item_type_from_id("1_story_simple"), "story");
    }

    // ── feature_branch_has_unmerged_changes tests ────────────────────────────

    fn init_git_repo(repo: &std::path::Path) {
        Command::new("git")
            .args(["init"])
            .current_dir(repo)
            .output()
            .unwrap();
        Command::new("git")
            .args(["config", "user.email", "test@test.com"])
            .current_dir(repo)
            .output()
            .unwrap();
        Command::new("git")
            .args(["config", "user.name", "Test"])
            .current_dir(repo)
            .output()
            .unwrap();
        Command::new("git")
            .args(["commit", "--allow-empty", "-m", "init"])
            .current_dir(repo)
            .output()
            .unwrap();
    }

    /// Bug 226: feature_branch_has_unmerged_changes returns true when the
    /// feature branch has commits not on master.
    #[test]
    fn feature_branch_has_unmerged_changes_detects_unmerged_code() {
        use std::fs;
        use tempfile::tempdir;

        let tmp = tempdir().unwrap();
        let repo = tmp.path();
        init_git_repo(repo);

        // Create a feature branch with a code commit.
        Command::new("git")
            .args(["checkout", "-b", "feature/story-50_story_test"])
            .current_dir(repo)
            .output()
            .unwrap();
        fs::write(repo.join("feature.rs"), "fn main() {}").unwrap();
        Command::new("git")
            .args(["add", "."])
            .current_dir(repo)
            .output()
            .unwrap();
        Command::new("git")
            .args(["commit", "-m", "add feature"])
            .current_dir(repo)
            .output()
            .unwrap();
        Command::new("git")
            .args(["checkout", "master"])
            .current_dir(repo)
            .output()
            .unwrap();

        assert!(
            feature_branch_has_unmerged_changes(repo, "50_story_test"),
            "should detect unmerged changes on feature branch"
        );
    }

    /// Bug 226: feature_branch_has_unmerged_changes returns false when no
    /// feature branch exists.
    #[test]
    fn feature_branch_has_unmerged_changes_false_when_no_branch() {
        use tempfile::tempdir;

        let tmp = tempdir().unwrap();
        let repo = tmp.path();
        init_git_repo(repo);

        assert!(
            !feature_branch_has_unmerged_changes(repo, "99_nonexistent"),
            "should return false when no feature branch"
        );
    }
}