//! Provider Key Pool 服务
//!
//! 管理 provider 的多个 API Key，实现智能轮转绕过限额。

use sqlx::PgPool;
use std::sync::OnceLock;
use std::time::{Duration, Instant};
use dashmap::DashMap;
use crate::error::{SaasError, SaasResult};
use crate::models::ProviderKeyRow;
use crate::crypto;

// ============ Key Pool Cache ============

/// TTL for cached key selections (seconds)
const KEY_CACHE_TTL: Duration = Duration::from_secs(5);

/// Cached key selection entry
struct CachedSelection {
    selection: KeySelection,
    cached_at: Instant,
}

/// Global cache for key selections, keyed by provider_id
static KEY_SELECTION_CACHE: OnceLock<DashMap<String, CachedSelection>> = OnceLock::new();

fn get_cache() -> &'static DashMap<String, CachedSelection> {
    KEY_SELECTION_CACHE.get_or_init(DashMap::new)
}

/// Invalidate cached selection for a provider (called on 429 marking)
fn invalidate_cache(provider_id: &str) {
    let cache = get_cache();
    cache.remove(provider_id);
}

/// 解密 key_value (如果已加密)，否则原样返回
fn decrypt_key_value(encrypted: &str, enc_key: &[u8; 32]) -> SaasResult<String> {
    if crypto::is_encrypted(encrypted) {
        crypto::decrypt_value(encrypted, enc_key)
            .map_err(|e| SaasError::Internal(e.to_string()))
    } else {
        // 兼容旧的明文格式
        Ok(encrypted.to_string())
    }
}

/// Key Pool 中的可用 Key
#[derive(Debug, Clone)]
pub struct PoolKey {
    pub id: String,
    pub key_value: String,
    pub priority: i32,
    pub max_rpm: Option<i64>,
    pub max_tpm: Option<i64>,
}

/// Key 选择结果
#[derive(Clone)]
pub struct KeySelection {
    pub key: PoolKey,
    pub key_id: String,
}

/// 从 provider 的 Key Pool 中选择最佳可用 Key
///
/// 优化: 单次 JOIN 查询获取 Key + 滑动窗口(60s) RPM/TPM 使用量
pub async fn select_best_key(db: &PgPool, provider_id: &str, enc_key: &[u8; 32]) -> SaasResult<KeySelection> {
    // Check in-memory cache first (TTL 5s)
    {
        let cache = get_cache();
        if let Some(entry) = cache.get(provider_id) {
            if entry.cached_at.elapsed() < KEY_CACHE_TTL {
                return Ok(entry.selection.clone());
            }
        }
    }

    let now = chrono::Utc::now();

    // 滑动窗口: 聚合最近 60 秒内所有窗口行的 RPM/TPM，避免分钟边界突发
    let rows: Vec<(String, String, i32, Option<i64>, Option<i64>, Option<i64>, Option<i64>)> =
        sqlx::query_as(
            "SELECT pk.id, pk.key_value, pk.priority, pk.max_rpm, pk.max_tpm,
                    COALESCE(SUM(uw.request_count), 0)::bigint,
                    COALESCE(SUM(uw.token_count), 0)::bigint
             FROM provider_keys pk
             LEFT JOIN key_usage_window uw ON pk.id = uw.key_id
               AND uw.window_minute >= to_char(NOW() - INTERVAL '1 minute', 'YYYY-MM-DDTHH24:MI')
             WHERE pk.provider_id = $1 AND pk.is_active = TRUE
               AND (pk.cooldown_until IS NULL OR pk.cooldown_until::timestamptz <= $2)
             GROUP BY pk.id, pk.key_value, pk.priority, pk.max_rpm, pk.max_tpm
             ORDER BY pk.priority ASC, pk.last_used_at ASC NULLS FIRST"
        ).bind(provider_id).bind(&now).fetch_all(db).await?;

    for (id, key_value, priority, max_rpm, max_tpm, req_count, token_count) in &rows {
        // RPM 检查
        if let Some(rpm_limit) = max_rpm {
            if *rpm_limit > 0 {
                let count = req_count.unwrap_or(0);
                if count >= *rpm_limit {
                    tracing::debug!("Key {} hit RPM limit ({}/{})", id, count, rpm_limit);
                    continue;
                }
            }
        }

        // TPM 检查
        if let Some(tpm_limit) = max_tpm {
            if *tpm_limit > 0 {
                let tokens = token_count.unwrap_or(0);
                if tokens >= *tpm_limit {
                    tracing::debug!("Key {} hit TPM limit ({}/{})", id, tokens, tpm_limit);
                    continue;
                }
            }
        }

        // 此 Key 可用 — 解密 key_value
        let decrypted_kv = match decrypt_key_value(key_value, enc_key) {
            Ok(v) => v,
            Err(e) => {
                tracing::warn!("Key {} decryption failed, skipping: {}", id, e);
                continue;
            }
        };
        let selection = KeySelection {
            key: PoolKey {
                id: id.clone(),
                key_value: decrypted_kv,
                priority: *priority,
                max_rpm: *max_rpm,
                max_tpm: *max_tpm,
            },
            key_id: id.clone(),
        };
        // Cache the selection
        get_cache().insert(provider_id.to_string(), CachedSelection {
            selection: selection.clone(),
            cached_at: Instant::now(),
        });
        return Ok(selection);
    }

    // 所有活跃 Key 都超限 — 先检查是否存在活跃 Key
    let has_any_active: Option<(bool,)> = sqlx::query_as(
        "SELECT COUNT(*) > 0 FROM provider_keys WHERE provider_id = $1 AND is_active = TRUE"
    ).bind(provider_id).fetch_optional(db).await?;

    if has_any_active.is_some_and(|(b,)| b) {
        // 有活跃 key 但全部 cooldown 或超限 — 检查最快恢复时间
        let cooldown_row: Option<(String,)> = sqlx::query_as(
            "SELECT cooldown_until::TEXT FROM provider_keys
             WHERE provider_id = $1 AND is_active = TRUE AND cooldown_until IS NOT NULL AND cooldown_until::timestamptz > $2
             ORDER BY cooldown_until ASC
             LIMIT 1"
        ).bind(provider_id).bind(&now).fetch_optional(db).await?;

        if let Some((earliest,)) = cooldown_row {
            let wait_secs = parse_cooldown_remaining(&earliest, &now.to_rfc3339());
            return Err(SaasError::RateLimited(
                format!("所有 Key 均在冷却中，预计 {} 秒后可用", wait_secs)
            ));
        }

        // Key 存在但 RPM/TPM 全部用尽（无 cooldown）
        return Err(SaasError::RateLimited(
            format!("Provider {} 所有 Key 均已达限额", provider_id)
        ));
    }

    // 没有活跃 Key — 自动恢复 cooldown 已过期但 is_active=false 的 Key
    let reactivated: Option<(i64,)> = sqlx::query_as(
        "UPDATE provider_keys SET is_active = TRUE, cooldown_until = NULL, updated_at = NOW()
         WHERE provider_id = $1 AND is_active = FALSE
           AND (cooldown_until IS NOT NULL AND cooldown_until::timestamptz <= $2)
         RETURNING (SELECT COUNT(*) FROM provider_keys WHERE provider_id = $1 AND is_active = TRUE)"
    ).bind(provider_id).bind(&now).fetch_optional(db).await?;

    if let Some((active_count,)) = &reactivated {
        if *active_count > 0 {
            tracing::info!(
                "Provider {} 自动恢复了 {} 个 cooldown 过期的 Key，重试选择",
                provider_id, active_count
            );
            invalidate_cache(provider_id);
            // 重试查询（不用递归，直接再走一次查询逻辑）
            let retry_rows: Vec<(String, String, i32, Option<i64>, Option<i64>, Option<i64>, Option<i64>)> =
                sqlx::query_as(
                    "SELECT pk.id, pk.key_value, pk.priority, pk.max_rpm, pk.max_tpm,
                            COALESCE(SUM(uw.request_count), 0)::bigint,
                            COALESCE(SUM(uw.token_count), 0)::bigint
                     FROM provider_keys pk
                     LEFT JOIN key_usage_window uw ON pk.id = uw.key_id
                       AND uw.window_minute >= to_char(NOW() - INTERVAL '1 minute', 'YYYY-MM-DDTHH24:MI')
                     WHERE pk.provider_id = $1 AND pk.is_active = TRUE
                       AND (pk.cooldown_until IS NULL OR pk.cooldown_until::timestamptz <= $2)
                     GROUP BY pk.id, pk.key_value, pk.priority, pk.max_rpm, pk.max_tpm
                     ORDER BY pk.priority ASC, pk.last_used_at ASC NULLS FIRST"
                ).bind(provider_id).bind(&now).fetch_all(db).await?;

            for (id, key_value, _priority, max_rpm, max_tpm, req_count, token_count) in &retry_rows {
                if let Some(rpm_limit) = max_rpm {
                    if *rpm_limit > 0 && req_count.unwrap_or(0) >= *rpm_limit { continue; }
                }
                if let Some(tpm_limit) = max_tpm {
                    if *tpm_limit > 0 && token_count.unwrap_or(0) >= *tpm_limit { continue; }
                }
                let decrypted_kv = match decrypt_key_value(key_value, enc_key) {
                    Ok(v) => v,
                    Err(_) => continue,
                };
                let selection = KeySelection {
                    key: PoolKey { id: id.clone(), key_value: decrypted_kv, priority: *_priority, max_rpm: *max_rpm, max_tpm: *max_tpm },
                    key_id: id.clone(),
                };
                get_cache().insert(provider_id.to_string(), CachedSelection {
                    selection: selection.clone(),
                    cached_at: Instant::now(),
                });
                return Ok(selection);
            }
        }
    }

    Err(SaasError::NotFound(format!(
        "Provider {} 没有可用的 API Key（所有 Key 已停用，请在管理后台激活）",
        provider_id
    )))
}

/// 记录 Key 使用量（滑动窗口）
/// 合并为 2 次查询：1 次 upsert 滑动窗口 + 1 次更新 provider_keys 累计统计（含 last_used_at）
pub async fn record_key_usage(
    db: &PgPool,
    key_id: &str,
    tokens: Option<i64>,
) -> SaasResult<()> {
    let current_minute = chrono::Utc::now().format("%Y-%m-%dT%H:%M").to_string();

    // 1. Upsert sliding window
    sqlx::query(
        "INSERT INTO key_usage_window (key_id, window_minute, request_count, token_count)
         VALUES ($1, $2, 1, $3)
         ON CONFLICT (key_id, window_minute) DO UPDATE
         SET request_count = key_usage_window.request_count + 1,
             token_count = key_usage_window.token_count + $3"
    )
    .bind(key_id).bind(&current_minute).bind(tokens.unwrap_or(0))
    .execute(db).await?;

    // 2. Update cumulative stats + last_used_at in one query
    sqlx::query(
        "UPDATE provider_keys
         SET total_requests = total_requests + 1,
             total_tokens = total_tokens + COALESCE($1, 0),
             last_used_at = NOW(),
             updated_at = NOW()
         WHERE id = $2"
    )
    .bind(tokens).bind(key_id)
    .execute(db).await?;

    // 3. 清理过期的滑动窗口行（保留最近 2 分钟即可）
    let _ = sqlx::query(
        "DELETE FROM key_usage_window WHERE window_minute < to_char(NOW() - INTERVAL '2 minutes', 'YYYY-MM-DDTHH24:MI')"
    )
    .execute(db).await; // 忽略错误，非关键操作

    Ok(())
}

/// 标记 Key 收到 429，设置冷却期
pub async fn mark_key_429(
    db: &PgPool,
    key_id: &str,
    retry_after_seconds: Option<u64>,
) -> SaasResult<()> {
    let cooldown = if let Some(secs) = retry_after_seconds {
        (chrono::Utc::now() + chrono::Duration::seconds(secs as i64))
    } else {
        // 默认 60 秒冷却（适合小配额 Coding Plan 账号）
        chrono::Utc::now() + chrono::Duration::seconds(60)
    };

    let now = chrono::Utc::now();

    sqlx::query(
        "UPDATE provider_keys SET last_429_at = $1, cooldown_until = $2, updated_at = $3
         WHERE id = $4"
    )
    .bind(&now).bind(&cooldown).bind(&now).bind(key_id)
    .execute(db).await?;

    tracing::warn!(
        "Key {} 收到 429，冷却至 {}",
        key_id,
        cooldown
    );

    // Invalidate cache for this key's provider (query provider_id then clear)
    let pid_result: Result<Option<(String,)>, _> = sqlx::query_as(
        "SELECT provider_id FROM provider_keys WHERE id = $1"
    ).bind(key_id).fetch_optional(db).await;
    if let Ok(Some((pid,))) = pid_result {
        invalidate_cache(&pid);
    }

    Ok(())
}

/// 获取 provider 的所有 Key（管理用）
pub async fn list_provider_keys(
    db: &PgPool,
    provider_id: &str,
) -> SaasResult<Vec<serde_json::Value>> {
    let rows: Vec<ProviderKeyRow> =
        sqlx::query_as(
            "SELECT id, provider_id, key_label, priority, max_rpm, max_tpm, is_active,
                   last_429_at::TEXT, cooldown_until::TEXT, total_requests, total_tokens, created_at::TEXT, updated_at::TEXT
             FROM provider_keys WHERE provider_id = $1 ORDER BY priority ASC"
        ).bind(provider_id).fetch_all(db).await?;

    Ok(rows.into_iter().map(|r| {
        serde_json::json!({
            "id": r.id,
            "provider_id": r.provider_id,
            "key_label": r.key_label,
            "priority": r.priority,
            "max_rpm": r.max_rpm,
            "max_tpm": r.max_tpm,
            "is_active": r.is_active,
            "last_429_at": r.last_429_at,
            "cooldown_until": r.cooldown_until,
            "total_requests": r.total_requests,
            "total_tokens": r.total_tokens,
            "created_at": r.created_at,
            "updated_at": r.updated_at,
        })
    }).collect())
}

/// 添加 Key 到 Pool
pub async fn add_provider_key(
    db: &PgPool,
    provider_id: &str,
    key_label: &str,
    key_value: &str,
    priority: i32,
    max_rpm: Option<i64>,
    max_tpm: Option<i64>,
) -> SaasResult<String> {
    let id = uuid::Uuid::new_v4().to_string();
    let now = chrono::Utc::now();

    sqlx::query(
        "INSERT INTO provider_keys (id, provider_id, key_label, key_value, priority, max_rpm, max_tpm, is_active, total_requests, total_tokens, created_at, updated_at)
         VALUES ($1, $2, $3, $4, $5, $6, $7, TRUE, 0, 0, $8, $8)"
    )
    .bind(&id).bind(provider_id).bind(key_label).bind(key_value)
    .bind(priority).bind(max_rpm).bind(max_tpm).bind(&now)
    .execute(db).await?;

    tracing::info!("Added key '{}' to provider {}", key_label, provider_id);
    Ok(id)
}

/// 切换 Key 活跃状态
pub async fn toggle_key_active(
    db: &PgPool,
    key_id: &str,
    active: bool,
) -> SaasResult<()> {
    let now = chrono::Utc::now();
    sqlx::query(
        "UPDATE provider_keys SET is_active = $1, updated_at = $2 WHERE id = $3"
    ).bind(active).bind(&now).bind(key_id).execute(db).await?;
    Ok(())
}

/// 删除 Key
pub async fn delete_provider_key(
    db: &PgPool,
    key_id: &str,
) -> SaasResult<()> {
    sqlx::query("DELETE FROM provider_keys WHERE id = $1")
        .bind(key_id).execute(db).await?;
    Ok(())
}

/// Key 使用窗口统计
#[derive(Debug, Clone)]
pub struct KeyUsageStats {
    pub key_id: String,
    pub window_minute: String,
    pub request_count: i32,
    pub token_count: i64,
}

/// 查询指定 Key 的最近使用窗口统计
pub async fn get_key_usage_stats(
    db: &PgPool,
    key_id: &str,
    limit: i64,
) -> SaasResult<Vec<KeyUsageStats>> {
    let limit = limit.min(60).max(1);
    let rows: Vec<(String, String, i32, i64)> = sqlx::query_as(
        "SELECT key_id, window_minute, request_count, token_count \
         FROM key_usage_window \
         WHERE key_id = $1 \
         ORDER BY window_minute DESC \
         LIMIT $2"
    )
    .bind(key_id)
    .bind(limit)
    .fetch_all(db)
    .await?;

    Ok(rows.into_iter().map(|(key_id, window_minute, request_count, token_count)| {
        KeyUsageStats { key_id, window_minute, request_count, token_count }
    }).collect())
}

/// 解析冷却剩余时间（秒）
fn parse_cooldown_remaining(cooldown_until: &str, now: &str) -> i64 {
    let cooldown = chrono::DateTime::parse_from_rfc3339(cooldown_until);
    let current = chrono::DateTime::parse_from_rfc3339(now);

    match (cooldown, current) {
        (Ok(c), Ok(n)) => {
            let diff = c.signed_duration_since(n);
            diff.num_seconds().max(0)
        }
        _ => 60, // 默认 60 秒
    }
}

/// Startup self-healing: re-encrypt all provider keys with current encryption key.
///
/// For each encrypted key, attempts decryption with the current key.
/// If decryption succeeds, re-encrypts and updates in-place (idempotent).
/// If decryption fails, logs a warning and marks the key inactive.
pub async fn heal_provider_keys(db: &PgPool, enc_key: &[u8; 32]) -> usize {
    let rows: Vec<(String, String)> = sqlx::query_as(
        "SELECT id, key_value FROM provider_keys WHERE key_value LIKE 'enc:%'"
    ).fetch_all(db).await.unwrap_or_default();

    let mut healed = 0usize;
    let mut failed = 0usize;

    for (id, key_value) in &rows {
        match crypto::decrypt_value(key_value, enc_key) {
            Ok(plaintext) => {
                // Re-encrypt with current key (idempotent if same key)
                match crypto::encrypt_value(&plaintext, enc_key) {
                    Ok(new_encrypted) => {
                        if let Err(e) = sqlx::query(
                            "UPDATE provider_keys SET key_value = $1 WHERE id = $2"
                        ).bind(&new_encrypted).bind(id).execute(db).await {
                            tracing::warn!("[heal] Failed to update key {}: {}", id, e);
                        } else {
                            healed += 1;
                        }
                    }
                    Err(e) => {
                        tracing::warn!("[heal] Failed to re-encrypt key {}: {}", id, e);
                        failed += 1;
                    }
                }
            }
            Err(e) => {
                tracing::warn!("[heal] Cannot decrypt key {}, marking inactive: {}", id, e);
                let _ = sqlx::query(
                    "UPDATE provider_keys SET is_active = FALSE WHERE id = $1"
                ).bind(id).execute(db).await;
                failed += 1;
            }
        }
    }

    if healed > 0 || failed > 0 {
        tracing::info!("[heal] Provider keys: {} re-encrypted, {} failed", healed, failed);
    }
    healed
}