//! Story lifecycle helpers — archival and stage transitions for pipeline items.
//!
//! All pipeline state lives in the CRDT.  These functions never consult the
//! filesystem for work-item data — CRDT lookup failures propagate as errors.
//!
//! Every lifecycle function routes through the typed state machine
//! ([`crate::pipeline_state::apply_transition`]) so that illegal transitions
//! are rejected and every stage change emits a [`TransitionFired`] event.
use std::num::NonZeroU32;
use std::path::Path;
use std::process::Command;

use crate::io::story_metadata::clear_front_matter_field_in_content;
use crate::pipeline_state::{
    ApplyError, ArchiveReason, BranchName, GitSha, PipelineEvent, Stage, apply_transition,
    stage_label,
};
use crate::slog;

/// Determine the item type ("story", "bug", "spike", or "refactor") from the item ID.
///
/// For slug-format IDs (e.g. `"4_bug_login_crash"`), the type is embedded in the ID.
/// For numeric-only IDs (e.g. `"4"`), the type is read from the `type:` field in
/// the content-store front matter.  Falls back to `"story"` if not found.
pub(crate) fn item_type_from_id(item_id: &str) -> &'static str {
    let after_num = item_id.trim_start_matches(|c: char| c.is_ascii_digit());
    if after_num.starts_with("_bug_") {
        return "bug";
    } else if after_num.starts_with("_spike_") {
        return "spike";
    } else if after_num.starts_with("_refactor_") {
        return "refactor";
    }
    // Numeric-only ID: check content store front matter for explicit type.
    if after_num.is_empty()
        && let Some(content) = crate::db::read_content(item_id)
        && let Ok(meta) = crate::io::story_metadata::parse_front_matter(&content)
        && let Some(t) = meta.item_type.as_deref()
    {
        return match t {
            "bug" => "bug",
            "spike" => "spike",
            "refactor" => "refactor",
            _ => "story",
        };
    }
    "story"
}

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

/// Build a content-transform closure that clears the given front-matter fields.
fn fields_to_clear_transform(fields: &[&str]) -> Option<ContentTransform> {
    if fields.is_empty() {
        return None;
    }
    let fields: Vec<String> = fields.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
    }))
}

/// Move a work item (story, bug, or spike) from `1_backlog` to `work/2_current/`.
///
/// Only promotes from `1_backlog` — stories already in later stages (3_qa, 4_merge,
/// etc.) are left untouched.  This prevents coders from accidentally demoting a story
/// that has already advanced past the coding stage.
/// Idempotent: if already in `2_current/`, returns Ok. If not found, logs and returns Ok.
pub fn move_story_to_current(story_id: &str) -> Result<(), String> {
    match apply_transition(story_id, PipelineEvent::DepsMet, None) {
        Ok(_) => Ok(()),
        Err(ApplyError::NotFound(_)) => {
            slog!("[lifecycle] Work item '{story_id}' not found; skipping move to work/2_current/");
            Ok(())
        }
        Err(ApplyError::InvalidTransition(_)) => {
            // Already promoted or in a later stage — idempotent no-op.
            Ok(())
        }
        Err(ApplyError::Projection(_)) => Ok(()),
    }
}

/// 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/`, `work/3_qa/`, or `work/4_merge/` to `work/5_done/`.
///
/// Idempotent if already in `5_done/` or `6_archived/`. Errors if not found in any earlier stage.
/// Spikes may transition directly from `3_qa/` to `5_done/`, skipping the merge stage.
pub fn move_story_to_done(story_id: &str) -> Result<(), String> {
    let item = read_typed_or_err(story_id)?;
    let dir = item.stage.dir_name();

    // Idempotent: already at or past done.
    if dir >= "5_done" {
        return Ok(());
    }

    let event = match &item.stage {
        Stage::Merge { .. } => PipelineEvent::MergeSucceeded {
            merge_commit: GitSha("accepted".to_string()),
        },
        Stage::Coding | Stage::Qa | Stage::Backlog => PipelineEvent::Close,
        _ => {
            return Err(format!(
                "Work item '{story_id}' is in {} — cannot move to done.",
                stage_label(&item.stage)
            ));
        }
    };

    let transform = fields_to_clear_transform(&["merge_failure", "blocked"]);
    apply_transition(story_id, event, transform.as_ref().map(|f| f.as_ref()))
        .map(|_| ())
        .map_err(|e| e.to_string())
}

/// 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(story_id: &str) -> Result<(), String> {
    let item = read_typed_or_err(story_id)?;
    let dir = item.stage.dir_name();

    // Idempotent: already at or past merge.
    if dir >= "4_merge" {
        return Ok(());
    }

    let branch = BranchName(format!("feature/story-{story_id}"));
    let commits = NonZeroU32::new(1).expect("1 is non-zero");

    let event = match &item.stage {
        Stage::Coding => PipelineEvent::QaSkipped {
            feature_branch: branch,
            commits_ahead: commits,
        },
        Stage::Qa => PipelineEvent::GatesPassed {
            feature_branch: branch,
            commits_ahead: commits,
        },
        _ => {
            return Err(format!(
                "Work item '{story_id}' not found in work/2_current/ or work/3_qa/."
            ));
        }
    };

    let transform = fields_to_clear_transform(&["blocked"]);
    apply_transition(story_id, event, transform.as_ref().map(|f| f.as_ref()))
        .map(|_| ())
        .map_err(|e| e.to_string())
}

/// 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(story_id: &str) -> Result<(), String> {
    let item = read_typed_or_err(story_id)?;
    let dir = item.stage.dir_name();

    // Idempotent: already at or past qa.
    if dir >= "3_qa" {
        return Ok(());
    }

    let transform = fields_to_clear_transform(&["blocked"]);
    apply_transition(
        story_id,
        PipelineEvent::GatesStarted,
        transform.as_ref().map(|f| f.as_ref()),
    )
    .map(|_| ())
    .map_err(|e| e.to_string())
}

/// Move a story from `work/3_qa/` back to `work/2_current/`, clearing `review_hold` and writing notes.
pub fn reject_story_from_qa(story_id: &str, notes: &str) -> Result<(), String> {
    let notes_owned = notes.to_string();
    let transform: Box<dyn Fn(&str) -> String> = Box::new(move |content: &str| {
        let mut result = clear_front_matter_field_in_content(content, "review_hold");
        if !notes_owned.is_empty() {
            result =
                crate::io::story_metadata::write_rejection_notes_to_content(&result, &notes_owned);
        }
        result
    });

    apply_transition(
        story_id,
        PipelineEvent::GatesFailed {
            reason: notes.to_string(),
        },
        Some(&*transform),
    )
    .map(|_| ())
    .map_err(|e| e.to_string())
}

/// Map a (current stage, target stage name) pair to the appropriate PipelineEvent.
fn map_stage_move_to_event(
    from: &Stage,
    target: &str,
    story_id: &str,
) -> Result<PipelineEvent, String> {
    let branch = || BranchName(format!("feature/story-{story_id}"));
    let nz1 = || NonZeroU32::new(1).expect("1 is non-zero");

    match (from, target) {
        (Stage::Upcoming, "backlog") => Ok(PipelineEvent::Triage),
        (Stage::Backlog, "current") => Ok(PipelineEvent::DepsMet),
        (Stage::Coding, "qa") => Ok(PipelineEvent::GatesStarted),
        (Stage::Coding, "merge") => Ok(PipelineEvent::QaSkipped {
            feature_branch: branch(),
            commits_ahead: nz1(),
        }),
        (Stage::Qa, "merge") => Ok(PipelineEvent::GatesPassed {
            feature_branch: branch(),
            commits_ahead: nz1(),
        }),
        (Stage::Coding, "backlog") | (Stage::Qa, "backlog") | (Stage::Merge { .. }, "backlog") => {
            Ok(PipelineEvent::Demote)
        }
        (Stage::Qa, "current") => Ok(PipelineEvent::GatesFailed {
            reason: "manual move".to_string(),
        }),
        (Stage::Merge { .. }, "done") => Ok(PipelineEvent::MergeSucceeded {
            merge_commit: GitSha("manual".to_string()),
        }),
        (Stage::Coding | Stage::Qa | Stage::Backlog, "done") => Ok(PipelineEvent::Close),
        (
            Stage::Archived {
                reason: ArchiveReason::Blocked { .. },
                ..
            },
            "backlog",
        )
        | (
            Stage::Archived {
                reason: ArchiveReason::MergeFailed { .. },
                ..
            },
            "backlog",
        ) => Ok(PipelineEvent::Unblock),
        _ => Err(format!(
            "Invalid target_stage '{target}'. Cannot transition from {} to {target}.",
            stage_label(from),
        )),
    }
}

/// 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(story_id: &str, target_stage: &str) -> Result<(String, String), String> {
    // Validate target.
    let target_dir = match target_stage {
        "backlog" => "1_backlog",
        "current" => "2_current",
        "qa" => "3_qa",
        "merge" => "4_merge",
        "done" => "5_done",
        _ => {
            return Err(format!(
                "Invalid target_stage '{target_stage}'. Must be one of: backlog, current, qa, merge, done"
            ));
        }
    };

    let item = read_typed_or_err(story_id)?;
    let from_name = stage_to_name(&item.stage);

    // Idempotent: already in the target stage.
    if item.stage.dir_name() == target_dir {
        return Ok((target_stage.to_string(), target_stage.to_string()));
    }

    let event = map_stage_move_to_event(&item.stage, target_stage, story_id)?;

    apply_transition(story_id, event, None).map_err(|e| e.to_string())?;

    Ok((from_name.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(bug_id: &str) -> Result<(), String> {
    let item = read_typed_or_err(bug_id)?;

    if item.stage.dir_name() >= "5_done" {
        return Ok(());
    }

    apply_transition(bug_id, PipelineEvent::Close, None)
        .map(|_| ())
        .map_err(|e| e.to_string())
}

/// Read a typed pipeline item or return a user-facing error.
fn read_typed_or_err(story_id: &str) -> Result<crate::pipeline_state::PipelineItem, String> {
    crate::pipeline_state::read_typed(story_id)
        .map_err(|e| format!("Work item '{story_id}': {e}"))?
        .ok_or_else(|| format!("Work item '{story_id}' not found in any pipeline stage."))
}

/// Map a Stage variant to the short name used by `move_story_to_stage` return values.
fn stage_to_name(s: &Stage) -> &'static str {
    match s {
        Stage::Upcoming => "upcoming",
        Stage::Backlog => "backlog",
        Stage::Coding => "current",
        Stage::Qa => "qa",
        Stage::Merge { .. } => "merge",
        Stage::Done { .. } => "done",
        Stage::Archived { .. } => "archived",
        Stage::Frozen { .. } => "frozen",
    }
}

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

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

    #[test]
    fn move_story_to_current_from_crdt() {
        // Seed via CRDT — the sole source of truth for pipeline state.
        crate::db::ensure_content_store();
        crate::db::write_item_with_content(
            "99950_story_lifecycle",
            "1_backlog",
            "---\nname: Lifecycle Test\n---\n# Story\n",
        );

        move_story_to_current("99950_story_lifecycle").unwrap();

        // Verify the CRDT now has the item in 2_current.
        let item = crate::pipeline_state::read_typed("99950_story_lifecycle")
            .expect("CRDT read should succeed")
            .expect("item should exist in CRDT after move");
        assert_eq!(
            item.stage.dir_name(),
            "2_current",
            "item should be in 2_current after move"
        );
    }

    #[test]
    fn move_story_to_current_noop_when_not_found() {
        assert!(move_story_to_current("99_missing").is_ok());
    }

    /// Lifecycle operation runs to completion using only CRDT state;
    /// no `.huskies/work/<stage>/` tree is consulted because no `project_root`
    /// is passed — the functions operate purely on the CRDT.
    #[test]
    fn move_story_uses_only_crdt_no_fs_shadow() {
        crate::db::ensure_content_store();
        crate::db::write_item_with_content(
            "99951_story_crdt_only",
            "2_current",
            "---\nname: CRDT Only Test\n---\n# Story\n",
        );

        // No filesystem path is involved — lifecycle functions no longer
        // accept a project_root, proving they never touch the filesystem.
        move_story_to_done("99951_story_crdt_only").unwrap();

        let item = crate::pipeline_state::read_typed("99951_story_crdt_only")
            .expect("CRDT read should succeed")
            .expect("item should exist in CRDT");
        assert_eq!(
            item.stage.dir_name(),
            "5_done",
            "item should be in 5_done after move"
        );
    }

    // ── 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");
        assert_eq!(item_type_from_id("1_refactor_cleanup"), "refactor");
    }

    #[test]
    fn item_type_from_id_falls_back_to_content_store_for_numeric_ids() {
        crate::db::ensure_content_store();

        // Write a bug item with numeric-only ID into the content store.
        let bug_content = "---\ntype: bug\nname: \"Test Bug\"\n---\n\n# Bug 9999: Test Bug\n";
        crate::db::write_content("9999", bug_content);

        let spike_content =
            "---\ntype: spike\nname: \"Test Spike\"\n---\n\n# Spike 9998: Test Spike\n";
        crate::db::write_content("9998", spike_content);

        let refactor_content =
            "---\ntype: refactor\nname: \"Test Refactor\"\n---\n\n# Refactor 9997: Test Refactor\n";
        crate::db::write_content("9997", refactor_content);

        let story_content =
            "---\ntype: story\nname: \"Test Story\"\n---\n\n# Story 9996: Test Story\n";
        crate::db::write_content("9996", story_content);

        assert_eq!(item_type_from_id("9999"), "bug");
        assert_eq!(item_type_from_id("9998"), "spike");
        assert_eq!(item_type_from_id("9997"), "refactor");
        assert_eq!(item_type_from_id("9996"), "story");
        // No content store entry → defaults to "story".
        assert_eq!(item_type_from_id("99999"), "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"
        );
    }
}