use crate::{
    db::Pool,
    error::{AppError, AppResult},
    models::achievement::{AchievementDefinition, PlayerAchievement},
    services::{club as club_svc, notification},
};
use anyhow::Context;
use sqlx::{Sqlite, Transaction};
use std::collections::{HashMap, HashSet};
use std::path::Path;
use uuid::Uuid;

pub fn load_achievement_definitions(data_dir: &str) -> anyhow::Result<Vec<AchievementDefinition>> {
    let dir = Path::new(data_dir).join("achievements");
    let mut defs = Vec::new();
    if !dir.exists() {
        return Ok(defs);
    }
    for entry in std::fs::read_dir(&dir)? {
        let entry = entry?;
        let path = entry.path();
        if path.extension().map(|e| e == "json").unwrap_or(false) {
            let content =
                std::fs::read_to_string(&path).with_context(|| format!("reading {:?}", path))?;
            let batch: Vec<AchievementDefinition> =
                serde_json::from_str(&content).with_context(|| format!("parsing {:?}", path))?;
            defs.extend(batch);
        }
    }
    Ok(defs)
}

/// Query the current value for the given trigger metric.
async fn metric_value(
    pool: &Pool,
    profile_id: &str,
    club_id: &str,
    trigger: &str,
) -> AppResult<i64> {
    let v: i64 =
        match trigger {
            "matches_played" => {
                sqlx::query_scalar("SELECT matches_played FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(pool)
                    .await?
                    .unwrap_or(0)
            }

            "matches_won" => {
                sqlx::query_scalar("SELECT matches_won FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(pool)
                    .await?
                    .unwrap_or(0)
            }

            "goals_scored" => {
                sqlx::query_scalar("SELECT goals_scored FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(pool)
                    .await?
                    .unwrap_or(0)
            }

            "packs_opened" => {
                sqlx::query_scalar("SELECT packs_opened FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(pool)
                    .await?
                    .unwrap_or(0)
            }

            "sbcs_completed" => {
                sqlx::query_scalar("SELECT sbcs_completed FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(pool)
                    .await?
                    .unwrap_or(0)
            }

            "cards_owned" => {
                sqlx::query_scalar("SELECT COUNT(*) FROM owned_cards WHERE club_id = ?")
                    .bind(club_id)
                    .fetch_one(pool)
                    .await?
            }

            "level" => sqlx::query_scalar("SELECT level FROM profiles WHERE id = ?")
                .bind(profile_id)
                .fetch_optional(pool)
                .await?
                .unwrap_or(1),

            "objectives_completed" => sqlx::query_scalar(
                "SELECT COUNT(*) FROM objective_progress WHERE profile_id = ? AND completed = 1",
            )
            .bind(profile_id)
            .fetch_one(pool)
            .await?,

            "drafts_completed" => sqlx::query_scalar(
                "SELECT COUNT(*) FROM draft_sessions WHERE profile_id = ? AND status = 'completed'",
            )
            .bind(profile_id)
            .fetch_one(pool)
            .await?,

            _ => 0,
        };
    Ok(v)
}

/// Check all achievement definitions and unlock any not yet earned.
/// Returns definitions of newly unlocked achievements.
pub async fn check_and_unlock(
    pool: &Pool,
    defs: &[AchievementDefinition],
    profile_id: &str,
    club_id: &str,
) -> AppResult<Vec<AchievementDefinition>> {
    if defs.is_empty() {
        return Ok(vec![]);
    }

    // Load already-unlocked IDs in one query
    let unlocked_ids: Vec<String> =
        sqlx::query_scalar("SELECT achievement_id FROM player_achievements")
            .fetch_all(pool)
            .await?;

    let unlocked_set: std::collections::HashSet<&str> =
        unlocked_ids.iter().map(|s| s.as_str()).collect();

    let candidates: Vec<&AchievementDefinition> = defs
        .iter()
        .filter(|d| !unlocked_set.contains(d.id.as_str()))
        .collect();

    if candidates.is_empty() {
        return Ok(vec![]);
    }

    // Group candidates by trigger to minimise DB round-trips
    let mut trigger_cache: std::collections::HashMap<String, i64> = Default::default();
    let mut newly_unlocked: Vec<AchievementDefinition> = Vec::new();
    let now = chrono::Utc::now().to_rfc3339();

    for def in candidates {
        let value = match trigger_cache.get(&def.trigger) {
            Some(&v) => v,
            None => {
                let v = metric_value(pool, profile_id, club_id, &def.trigger).await?;
                trigger_cache.insert(def.trigger.clone(), v);
                v
            }
        };

        if value >= def.threshold {
            let pa_id = Uuid::new_v4().to_string();
            sqlx::query(
                "INSERT OR IGNORE INTO player_achievements (id, achievement_id, unlocked_at) VALUES (?, ?, ?)",
            )
            .bind(&pa_id)
            .bind(&def.id)
            .bind(&now)
            .execute(pool)
            .await?;

            if def.reward_coins > 0 {
                club_svc::add_coins(pool, club_id, def.reward_coins).await?;
            }

            let body = format!("{} Reward: {} coins.", def.description, def.reward_coins);
            let _ = notification::create(
                pool,
                "achievement",
                &format!("Achievement: {}", def.title),
                &body,
            )
            .await;

            newly_unlocked.push(def.clone());
        }
    }

    Ok(newly_unlocked)
}

/// Transaction-scoped [`metric_value`] — identical reads, run inside the
/// caller's transaction so achievement checks see the same uncommitted state the
/// rest of the match-completion transaction just wrote.
async fn metric_value_tx(
    tx: &mut Transaction<'_, Sqlite>,
    profile_id: &str,
    club_id: &str,
    trigger: &str,
) -> AppResult<i64> {
    let v: i64 =
        match trigger {
            "matches_played" => {
                sqlx::query_scalar("SELECT matches_played FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(&mut **tx)
                    .await?
                    .unwrap_or(0)
            }
            "matches_won" => {
                sqlx::query_scalar("SELECT matches_won FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(&mut **tx)
                    .await?
                    .unwrap_or(0)
            }
            "goals_scored" => {
                sqlx::query_scalar("SELECT goals_scored FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(&mut **tx)
                    .await?
                    .unwrap_or(0)
            }
            "packs_opened" => {
                sqlx::query_scalar("SELECT packs_opened FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(&mut **tx)
                    .await?
                    .unwrap_or(0)
            }
            "sbcs_completed" => {
                sqlx::query_scalar("SELECT sbcs_completed FROM statistics WHERE profile_id = ?")
                    .bind(profile_id)
                    .fetch_optional(&mut **tx)
                    .await?
                    .unwrap_or(0)
            }
            "cards_owned" => {
                sqlx::query_scalar("SELECT COUNT(*) FROM owned_cards WHERE club_id = ?")
                    .bind(club_id)
                    .fetch_one(&mut **tx)
                    .await?
            }
            "level" => sqlx::query_scalar("SELECT level FROM profiles WHERE id = ?")
                .bind(profile_id)
                .fetch_optional(&mut **tx)
                .await?
                .unwrap_or(1),
            "objectives_completed" => sqlx::query_scalar(
                "SELECT COUNT(*) FROM objective_progress WHERE profile_id = ? AND completed = 1",
            )
            .bind(profile_id)
            .fetch_one(&mut **tx)
            .await?,
            "drafts_completed" => sqlx::query_scalar(
                "SELECT COUNT(*) FROM draft_sessions WHERE profile_id = ? AND status = 'completed'",
            )
            .bind(profile_id)
            .fetch_one(&mut **tx)
            .await?,
            _ => 0,
        };
    Ok(v)
}

/// Transaction-scoped [`check_and_unlock`] for the atomic match-completion path.
/// Unlocks are inserted, coins credited, and notifications written inside the
/// caller's transaction (mirroring the inline economy writes elsewhere), so a
/// later failure rolls back the whole match — no half-granted achievement.
pub async fn check_and_unlock_tx(
    tx: &mut Transaction<'_, Sqlite>,
    defs: &[AchievementDefinition],
    profile_id: &str,
    club_id: &str,
    now: &str,
) -> AppResult<Vec<AchievementDefinition>> {
    if defs.is_empty() {
        return Ok(vec![]);
    }

    let unlocked_ids: Vec<String> =
        sqlx::query_scalar("SELECT achievement_id FROM player_achievements")
            .fetch_all(&mut **tx)
            .await?;
    let unlocked_set: HashSet<&str> = unlocked_ids.iter().map(|s| s.as_str()).collect();

    let candidates: Vec<&AchievementDefinition> = defs
        .iter()
        .filter(|d| !unlocked_set.contains(d.id.as_str()))
        .collect();
    if candidates.is_empty() {
        return Ok(vec![]);
    }

    let mut trigger_cache: HashMap<String, i64> = Default::default();
    let mut newly_unlocked: Vec<AchievementDefinition> = Vec::new();

    for def in candidates {
        let value = match trigger_cache.get(&def.trigger) {
            Some(&v) => v,
            None => {
                let v = metric_value_tx(tx, profile_id, club_id, &def.trigger).await?;
                trigger_cache.insert(def.trigger.clone(), v);
                v
            }
        };

        if value >= def.threshold {
            if def.reward_coins < 0 {
                return Err(AppError::Internal(anyhow::anyhow!(
                    "achievement {} has a negative reward",
                    def.id
                )));
            }
            let inserted = sqlx::query(
                "INSERT OR IGNORE INTO player_achievements (id, achievement_id, unlocked_at) VALUES (?, ?, ?)",
            )
            .bind(Uuid::new_v4().to_string())
            .bind(&def.id)
            .bind(now)
            .execute(&mut **tx)
            .await?;
            if inserted.rows_affected() == 0 {
                continue;
            }

            if def.reward_coins > 0 {
                let credited =
                    sqlx::query("UPDATE clubs SET coins = coins + ?, updated_at = ? WHERE id = ?")
                        .bind(def.reward_coins)
                        .bind(now)
                        .bind(club_id)
                        .execute(&mut **tx)
                        .await?;
                if credited.rows_affected() != 1 {
                    return Err(AppError::NotFound("club not found".into()));
                }
            }

            let body = format!("{} Reward: {} coins.", def.description, def.reward_coins);
            sqlx::query(
                "INSERT INTO notifications (id, kind, title, body, is_read, created_at) VALUES (?, 'achievement', ?, ?, 0, ?)",
            )
            .bind(Uuid::new_v4().to_string())
            .bind(format!("Achievement: {}", def.title))
            .bind(body)
            .bind(now)
            .execute(&mut **tx)
            .await?;

            newly_unlocked.push(def.clone());
        }
    }

    Ok(newly_unlocked)
}

/// Return all achievement definitions annotated with unlock status.
pub async fn list_with_status(
    pool: &Pool,
    defs: &[AchievementDefinition],
) -> AppResult<Vec<serde_json::Value>> {
    let earned: Vec<PlayerAchievement> = sqlx::query_as::<_, PlayerAchievement>(
        "SELECT id, achievement_id, unlocked_at FROM player_achievements",
    )
    .fetch_all(pool)
    .await?;

    let earned_map: std::collections::HashMap<&str, &str> = earned
        .iter()
        .map(|pa| (pa.achievement_id.as_str(), pa.unlocked_at.as_str()))
        .collect();

    Ok(defs
        .iter()
        .map(|d| {
            let unlocked_at = earned_map.get(d.id.as_str()).copied();
            serde_json::json!({
                "id": d.id,
                "title": d.title,
                "description": d.description,
                "icon": d.icon,
                "trigger": d.trigger,
                "threshold": d.threshold,
                "reward_coins": d.reward_coins,
                "rarity": d.rarity,
                "unlocked": unlocked_at.is_some(),
                "unlocked_at": unlocked_at,
            })
        })
        .collect())
}