//! Epic work-item MCP tools — create, list, and show epics.
//!
//! Epics are shared-context containers that group related stories, bugs, spikes,
//! and refactors. They are not pipeline-driven but provide authoritative context
//! injected into agent prompts for all member work items.

// Epic mechanism (item_type, epic link) has no CRDT register yet — story 933.
// parse_front_matter calls here are wrapped in `yaml_residue` so they're
// grep-findable until 933 lands.
use crate::db::yaml_legacy::{parse_front_matter, yaml_residue};
use crate::http::context::AppContext;
use crate::http::workflow::create_epic_file;
use serde_json::{Value, json};

/// Create a new epic and store it in the CRDT items list.
pub(crate) fn tool_create_epic(args: &Value, ctx: &AppContext) -> Result<String, String> {
    let name = args
        .get("name")
        .and_then(|v| v.as_str())
        .ok_or("Missing required argument: name")?;
    let goal = args
        .get("goal")
        .and_then(|v| v.as_str())
        .ok_or("Missing required argument: goal")?;
    let motivation = args.get("motivation").and_then(|v| v.as_str());
    let key_files = args.get("key_files").and_then(|v| v.as_str());
    let success_criteria: Option<Vec<String>> = args
        .get("success_criteria")
        .and_then(|v| v.as_array())
        .map(|arr| {
            arr.iter()
                .filter_map(|v| v.as_str().map(str::to_string))
                .collect()
        });

    let root = ctx.state.get_project_root()?;

    let epic_id = create_epic_file(
        &root,
        name,
        goal,
        motivation,
        key_files,
        success_criteria.as_deref(),
    )?;

    Ok(format!("Created epic: {epic_id}"))
}

/// List all epics with member work item counts and `n/m done` rollup.
pub(crate) fn tool_list_epics(_ctx: &AppContext) -> Result<String, String> {
    use crate::pipeline_state::Stage;

    let all_items = crate::pipeline_state::read_all_typed();

    // Collect epics: items with type == "epic".
    let mut epics: Vec<(String, String)> = Vec::new(); // (id, name)
    // Collect member items: map from epic_id → list of (story_id, is_done).
    let mut members: std::collections::HashMap<String, Vec<(String, bool)>> =
        std::collections::HashMap::new();

    for item in &all_items {
        let sid = &item.story_id.0;
        let content = match crate::db::read_content(sid) {
            Some(c) => c,
            None => continue,
        };
        let meta = match yaml_residue(parse_front_matter(&content)) {
            Ok(m) => m,
            Err(_) => continue,
        };

        if meta.item_type.as_deref() == Some("epic") {
            epics.push((sid.clone(), item.name.clone()));
        }

        if let Some(epic_id) = meta.epic {
            let is_done = matches!(item.stage, Stage::Done { .. });
            members
                .entry(epic_id)
                .or_default()
                .push((sid.clone(), is_done));
        }
    }

    epics.sort_by(|a, b| a.0.cmp(&b.0));

    let result: Vec<Value> = epics
        .iter()
        .map(|(id, name)| {
            let member_list = members.get(id).cloned().unwrap_or_default();
            let total = member_list.len();
            let done = member_list.iter().filter(|(_, d)| *d).count();
            json!({
                "epic_id": id,
                "name": name,
                "members_total": total,
                "members_done": done,
                "rollup": format!("{done}/{total} done"),
            })
        })
        .collect();

    serde_json::to_string_pretty(&result).map_err(|e| format!("Serialization error: {e}"))
}

/// Show details for a single epic: content and member work items with their stages.
pub(crate) fn tool_show_epic(args: &Value, _ctx: &AppContext) -> Result<String, String> {
    use crate::pipeline_state::Stage;

    let epic_id = args
        .get("epic_id")
        .and_then(|v| v.as_str())
        .ok_or("Missing required argument: epic_id")?;

    let content = crate::db::read_content(epic_id)
        .ok_or_else(|| format!("Epic '{epic_id}' not found in content store"))?;

    let meta = yaml_residue(parse_front_matter(&content))
        .map_err(|e| format!("Failed to parse epic front matter: {e}"))?;

    if meta.item_type.as_deref() != Some("epic") {
        return Err(format!(
            "'{epic_id}' is not an epic (type: {:?})",
            meta.item_type
        ));
    }

    // Find member items.
    let all_items = crate::pipeline_state::read_all_typed();
    let mut member_items: Vec<Value> = Vec::new();
    for item in &all_items {
        let sid = &item.story_id.0;
        let member_content = match crate::db::read_content(sid) {
            Some(c) => c,
            None => continue,
        };
        let member_meta = match yaml_residue(parse_front_matter(&member_content)) {
            Ok(m) => m,
            Err(_) => continue,
        };
        if member_meta.epic.as_deref() == Some(epic_id) {
            let stage_name = match &item.stage {
                Stage::Upcoming | Stage::Backlog => "backlog",
                Stage::Coding => "current",
                Stage::Qa => "qa",
                Stage::Merge { .. } => "merge",
                Stage::Done { .. } => "done",
                Stage::Archived { .. } => "archived",
                Stage::MergeFailure { .. } => "merge_failure",
                Stage::Frozen { .. } => "frozen",
                Stage::Blocked { .. } => "blocked",
            };
            member_items.push(json!({
                "story_id": sid,
                "name": item.name,
                "stage": stage_name,
            }));
        }
    }

    let total = member_items.len();
    let done = member_items.iter().filter(|i| i["stage"] == "done").count();

    serde_json::to_string_pretty(&json!({
        "epic_id": epic_id,
        "name": meta.name,
        "content": content,
        "members": member_items,
        "rollup": format!("{done}/{total} done"),
    }))
    .map_err(|e| format!("Serialization error: {e}"))
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::http::test_helpers::test_ctx;
    use serde_json::json;

    #[test]
    fn tool_create_epic_creates_epic_and_returns_id() {
        let tmp = tempfile::tempdir().unwrap();
        crate::db::ensure_content_store();
        let ctx = test_ctx(tmp.path());

        let result = tool_create_epic(
            &json!({
                "name": "My Test Epic",
                "goal": "Achieve something great",
                "motivation": "Because it matters",
                "success_criteria": ["All stories done", "Tests pass"]
            }),
            &ctx,
        );
        assert!(result.is_ok(), "expected ok: {result:?}");
        let msg = result.unwrap();
        assert!(msg.contains("Created epic:"), "unexpected msg: {msg}");
    }

    #[test]
    fn tool_create_epic_missing_name_returns_error() {
        let tmp = tempfile::tempdir().unwrap();
        let ctx = test_ctx(tmp.path());

        let result = tool_create_epic(&json!({"goal": "Achieve something"}), &ctx);
        assert!(result.is_err());
        assert!(result.unwrap_err().contains("name"));
    }

    #[test]
    fn tool_create_epic_missing_goal_returns_error() {
        let tmp = tempfile::tempdir().unwrap();
        let ctx = test_ctx(tmp.path());

        let result = tool_create_epic(&json!({"name": "My Epic"}), &ctx);
        assert!(result.is_err());
        assert!(result.unwrap_err().contains("goal"));
    }

    #[test]
    fn tool_list_epics_includes_created_epic() {
        let tmp = tempfile::tempdir().unwrap();
        crate::db::ensure_content_store();
        let ctx = test_ctx(tmp.path());

        // Create an epic.
        tool_create_epic(
            &json!({"name": "List Epics Test Epic", "goal": "Testing list"}),
            &ctx,
        )
        .unwrap();

        let result = tool_list_epics(&ctx);
        assert!(result.is_ok(), "expected ok: {result:?}");
        let parsed: Vec<Value> = serde_json::from_str(&result.unwrap()).unwrap();
        assert!(
            parsed.iter().any(|e| e["name"] == "List Epics Test Epic"),
            "expected epic in list: {parsed:?}"
        );
    }

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

        // Write a fake epic.
        crate::db::write_item_with_content(
            "9990_epic_rollup",
            "1_backlog",
            "---\ntype: epic\nname: \"Rollup Epic\"\n---\n\n## Goal\n\nTest\n",
            crate::db::ItemMeta::from_yaml(
                "---\ntype: epic\nname: \"Rollup Epic\"\n---\n\n## Goal\n\nTest\n",
            ),
        );
        // Write two member items: one done, one current.
        crate::db::write_item_with_content(
            "9991_story_member_done",
            "5_done",
            "---\ntype: story\nname: \"Done Member\"\nepic: \"9990_epic_rollup\"\n---\n",
            crate::db::ItemMeta::from_yaml(
                "---\ntype: story\nname: \"Done Member\"\nepic: \"9990_epic_rollup\"\n---\n",
            ),
        );
        crate::db::write_item_with_content(
            "9992_story_member_current",
            "2_current",
            "---\ntype: story\nname: \"Current Member\"\nepic: \"9990_epic_rollup\"\n---\n",
            crate::db::ItemMeta::from_yaml(
                "---\ntype: story\nname: \"Current Member\"\nepic: \"9990_epic_rollup\"\n---\n",
            ),
        );

        let tmp = tempfile::tempdir().unwrap();
        let ctx = crate::http::test_helpers::test_ctx(tmp.path());
        let result = tool_list_epics(&ctx).unwrap();
        let parsed: Vec<Value> = serde_json::from_str(&result).unwrap();
        let epic = parsed
            .iter()
            .find(|e| e["epic_id"] == "9990_epic_rollup")
            .expect("expected rollup epic in list");
        assert_eq!(epic["members_total"], 2, "two members expected");
        assert_eq!(epic["members_done"], 1, "one done member expected");
        assert_eq!(epic["rollup"], "1/2 done");
    }
}