package usage

import (
	"context"
	"database/sql"
	"fmt"
	"time"

	dbx "github.com/wangjia/pangolin/server/internal/db"
)

// Unlimited is the sentinel returned by CheckFreeConnect for plans with no
// daily-minute cap (pro / team).  Callers (e.g. the connect endpoint) treat it
// as "no minute limit; use the default paid credential TTL".
const Unlimited = -1

// dateLayout is the canonical UTC day format used as the usage_daily.date key
// and in the API response.
const dateLayout = "2006-01-02"

// Plan is the minimal subset of the plans row needed for quota decisions.
type Plan struct {
	Code         string        // free | pro | team
	DailyMinutes sql.NullInt64 // free=10; NULL = unlimited
	AdGate       bool          // free=true: daily rewarded-ad unlock required
}

// DailyUsage mirrors a usage_daily row.  It carries only aggregate byte and
// minute counts plus the ad-unlock timestamp — never destinations or DNS, per
// the no-log policy.
type DailyUsage struct {
	Date           time.Time
	BytesUp        uint64
	BytesDown      uint64
	MinutesUsed    int
	AdBonusMinutes int // 当日看广告累加解锁的额外分钟(免费版加时)
	AdUnlockedAt   sql.NullTime
}

// Store wraps a *sql.DB and exposes the usage_daily / plans / users queries the
// usage package needs.
type Store struct {
	db      *sql.DB
	dialect dbx.Dialect
}

// NewStore creates a Store backed by the given connection pool (MySQL or SQLite).
func NewStore(db *sql.DB) *Store { return &Store{db: db, dialect: dbx.DialectForDB(db)} }

// AggregateUsage accumulates one usage delta into usage_daily for (userID, day)
// using INSERT … ON DUPLICATE KEY UPDATE so concurrent reports from multiple
// nodes add up correctly.  day is truncated to its UTC calendar date.
func (s *Store) AggregateUsage(ctx context.Context, userID int64, day time.Time, bytesUp, bytesDown uint64, minutes int) error {
	d := day.UTC().Format(dateLayout)
	_, err := s.db.ExecContext(ctx,
		`INSERT INTO usage_daily (user_id, date, bytes_up, bytes_down, minutes_used)
		 VALUES (?, ?, ?, ?, ?)
		 `+s.dialect.Upsert([]string{"user_id", "date"},
			"bytes_up = bytes_up + EXCLUDED.bytes_up",
			"bytes_down = bytes_down + EXCLUDED.bytes_down",
			"minutes_used = minutes_used + EXCLUDED.minutes_used"),
		userID, d, bytesUp, bytesDown, minutes)
	if err != nil {
		return fmt.Errorf("store.AggregateUsage: %w", err)
	}
	return nil
}

// LookupUserIDByDPUUID resolves a data-plane credential UUID to the owning
// user_id.  Returns (0, nil) when no user matches (e.g. a rotated/stale dp_uuid)
// so the caller can decide to silently drop the report.
func (s *Store) LookupUserIDByDPUUID(ctx context.Context, dpUUID string) (int64, error) {
	var id int64
	err := s.db.QueryRowContext(ctx,
		`SELECT id FROM users WHERE dp_uuid = ? LIMIT 1`, dpUUID).Scan(&id)
	if err == sql.ErrNoRows {
		return 0, nil
	}
	if err != nil {
		return 0, fmt.Errorf("store.LookupUserIDByDPUUID: %w", err)
	}
	return id, nil
}

// GetUsageRange returns the usage_daily rows for userID with date in
// [from, to] (inclusive, UTC dates), ordered ascending.  Missing days are NOT
// filled here; zero-filling is the handler's responsibility.
func (s *Store) GetUsageRange(ctx context.Context, userID int64, from, to time.Time) ([]DailyUsage, error) {
	rows, err := s.db.QueryContext(ctx,
		`SELECT date, bytes_up, bytes_down, minutes_used, ad_bonus_minutes, ad_unlocked_at
		 FROM usage_daily
		 WHERE user_id = ? AND date BETWEEN ? AND ?
		 ORDER BY date ASC`,
		userID, from.UTC().Format(dateLayout), to.UTC().Format(dateLayout))
	if err != nil {
		return nil, fmt.Errorf("store.GetUsageRange: %w", err)
	}
	defer rows.Close()

	var out []DailyUsage
	for rows.Next() {
		var u DailyUsage
		if err := rows.Scan(&u.Date, &u.BytesUp, &u.BytesDown, &u.MinutesUsed, &u.AdBonusMinutes, &u.AdUnlockedAt); err != nil {
			return nil, fmt.Errorf("store.GetUsageRange scan: %w", err)
		}
		out = append(out, u)
	}
	return out, rows.Err()
}

// HourBucket is one UTC epoch-hour's account usage (read from usage_hourly).
type HourBucket struct {
	Hour        int64 // unix epoch hour (UTC) = floor(unix_seconds / 3600)
	BytesUp     uint64
	BytesDown   uint64
	MinutesUsed int
}

// HourlyRange returns usage_hourly rows for userID with hour in [fromHour, toHour]
// (inclusive, epoch hours), oldest first. Empty hours are simply absent.
func (s *Store) HourlyRange(ctx context.Context, userID, fromHour, toHour int64) ([]HourBucket, error) {
	rows, err := s.db.QueryContext(ctx,
		`SELECT hour, bytes_up, bytes_down, minutes_used
		 FROM usage_hourly
		 WHERE user_id = ? AND hour BETWEEN ? AND ?
		 ORDER BY hour ASC`,
		userID, fromHour, toHour)
	if err != nil {
		return nil, fmt.Errorf("store.HourlyRange: %w", err)
	}
	defer rows.Close()
	var out []HourBucket
	for rows.Next() {
		var b HourBucket
		if err := rows.Scan(&b.Hour, &b.BytesUp, &b.BytesDown, &b.MinutesUsed); err != nil {
			return nil, fmt.Errorf("store.HourlyRange scan: %w", err)
		}
		out = append(out, b)
	}
	return out, rows.Err()
}

// DeviceHourlyRange returns one device's UTC hourly buckets (usage_device_hourly)
// for hour in [fromHour, toHour], oldest first. The JOIN both resolves the
// client-facing device UUID to its internal id and enforces ownership (user_id),
// so a user can never read another user's device curve.
func (s *Store) DeviceHourlyRange(ctx context.Context, userID int64, deviceUUID string, fromHour, toHour int64) ([]HourBucket, error) {
	rows, err := s.db.QueryContext(ctx,
		`SELECT uh.hour, uh.bytes_up, uh.bytes_down, uh.minutes_used
		 FROM usage_device_hourly uh
		 JOIN devices d ON d.id = uh.device_id
		 WHERE d.user_id = ? AND d.uuid = ? AND uh.hour BETWEEN ? AND ?
		 ORDER BY uh.hour ASC`,
		userID, deviceUUID, fromHour, toHour)
	if err != nil {
		return nil, fmt.Errorf("store.DeviceHourlyRange: %w", err)
	}
	defer rows.Close()
	var out []HourBucket
	for rows.Next() {
		var b HourBucket
		if err := rows.Scan(&b.Hour, &b.BytesUp, &b.BytesDown, &b.MinutesUsed); err != nil {
			return nil, fmt.Errorf("store.DeviceHourlyRange scan: %w", err)
		}
		out = append(out, b)
	}
	return out, rows.Err()
}

// DeviceUsageRow is one device's aggregated usage over a date window, joined to
// the devices table for display metadata.  It is the per-device ("下分设备")
// counterpart of DailyUsage's account rollup.
type DeviceUsageRow struct {
	UUID        string
	Name        string
	Platform    string
	BytesUp     uint64
	BytesDown   uint64
	MinutesUsed int
}

// DeviceUsageRange returns each device's summed usage over [from, to] (inclusive
// UTC dates) for userID, one row per device, ordered by total bytes descending.
// Devices with no usage in the window are omitted.  All non-aggregate columns
// are in GROUP BY for MySQL ONLY_FULL_GROUP_BY portability (sqlite tolerant).
func (s *Store) DeviceUsageRange(ctx context.Context, userID int64, from, to time.Time) ([]DeviceUsageRow, error) {
	rows, err := s.db.QueryContext(ctx,
		`SELECT d.uuid, d.name, d.platform,
		        SUM(ud.bytes_up), SUM(ud.bytes_down), SUM(ud.minutes_used)
		 FROM usage_device_daily ud
		 JOIN devices d ON d.id = ud.device_id
		 WHERE ud.user_id = ? AND ud.date BETWEEN ? AND ?
		 GROUP BY ud.device_id, d.uuid, d.name, d.platform
		 ORDER BY (SUM(ud.bytes_up) + SUM(ud.bytes_down)) DESC`,
		userID, from.UTC().Format(dateLayout), to.UTC().Format(dateLayout))
	if err != nil {
		return nil, fmt.Errorf("store.DeviceUsageRange: %w", err)
	}
	defer rows.Close()

	var out []DeviceUsageRow
	for rows.Next() {
		var r DeviceUsageRow
		if err := rows.Scan(&r.UUID, &r.Name, &r.Platform, &r.BytesUp, &r.BytesDown, &r.MinutesUsed); err != nil {
			return nil, fmt.Errorf("store.DeviceUsageRange scan: %w", err)
		}
		out = append(out, r)
	}
	return out, rows.Err()
}

// GetDay returns the usage_daily row for (userID, day), or nil if none exists.
func (s *Store) GetDay(ctx context.Context, userID int64, day time.Time) (*DailyUsage, error) {
	var u DailyUsage
	err := s.db.QueryRowContext(ctx,
		`SELECT date, bytes_up, bytes_down, minutes_used, ad_bonus_minutes, ad_unlocked_at
		 FROM usage_daily
		 WHERE user_id = ? AND date = ?`,
		userID, day.UTC().Format(dateLayout)).
		Scan(&u.Date, &u.BytesUp, &u.BytesDown, &u.MinutesUsed, &u.AdBonusMinutes, &u.AdUnlockedAt)
	if err == sql.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("store.GetDay: %w", err)
	}
	return &u, nil
}

// AddAdBonusMinutes adds `add` minutes to usage_daily.ad_bonus_minutes for
// (userID, day), capped so the day's total bonus never exceeds `ceiling`.  It
// returns the new bonus total and the minutes actually granted this call
// (granted = newBonus − previous, i.e. 0 when the ceiling was already reached).
// Runs inside a transaction with SELECT … FOR UPDATE so concurrent ad-unlocks
// accumulate correctly (免费版累加式看广告加时).
//
// This is the additive successor to MarkAdUnlocked's per-day boolean unlock:
// each rewarded ad grants +add minutes (repeatable) up to the daily ceiling.
func (s *Store) AddAdBonusMinutes(ctx context.Context, userID int64, day time.Time, add, ceiling int) (newBonus, granted int, err error) {
	d := day.UTC().Format(dateLayout)

	tx, err := s.db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelReadCommitted})
	if err != nil {
		return 0, 0, fmt.Errorf("store.AddAdBonusMinutes begin: %w", err)
	}
	committed := false
	defer func() {
		if !committed {
			_ = tx.Rollback()
		}
	}()

	var cur int
	row := tx.QueryRowContext(ctx,
		`SELECT ad_bonus_minutes FROM usage_daily WHERE user_id = ? AND date = ? `+s.dialect.LockForUpdate(),
		userID, d)
	switch scanErr := row.Scan(&cur); scanErr {
	case nil:
		newBonus = cur + add
		if ceiling > 0 && newBonus > ceiling {
			newBonus = ceiling
		}
		if newBonus != cur {
			if _, uErr := tx.ExecContext(ctx,
				`UPDATE usage_daily SET ad_bonus_minutes = ? WHERE user_id = ? AND date = ?`,
				newBonus, userID, d); uErr != nil {
				return 0, 0, fmt.Errorf("store.AddAdBonusMinutes update: %w", uErr)
			}
		}
	case sql.ErrNoRows:
		cur = 0
		newBonus = add
		if ceiling > 0 && newBonus > ceiling {
			newBonus = ceiling
		}
		if _, iErr := tx.ExecContext(ctx,
			`INSERT INTO usage_daily (user_id, date, ad_bonus_minutes) VALUES (?, ?, ?)`,
			userID, d, newBonus); iErr != nil {
			return 0, 0, fmt.Errorf("store.AddAdBonusMinutes insert: %w", iErr)
		}
	default:
		return 0, 0, fmt.Errorf("store.AddAdBonusMinutes select: %w", scanErr)
	}

	if cErr := tx.Commit(); cErr != nil {
		return 0, 0, fmt.Errorf("store.AddAdBonusMinutes commit: %w", cErr)
	}
	committed = true
	return newBonus, newBonus - cur, nil
}

// MarkAdUnlocked sets usage_daily.ad_unlocked_at for (userID, day) to now if it
// is not already set.  It returns alreadyUnlocked=true when the day was already
// unlocked (making a second call idempotent).  Runs inside a transaction with
// SELECT … FOR UPDATE to be safe under concurrent unlock attempts.
//
// Deprecated: the免费版 ad model moved from a per-day boolean unlock to additive
// minutes (see AddAdBonusMinutes). Retained only for backward compatibility.
func (s *Store) MarkAdUnlocked(ctx context.Context, userID int64, day time.Time) (alreadyUnlocked bool, err error) {
	d := day.UTC().Format(dateLayout)
	now := time.Now().UTC()

	tx, err := s.db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelReadCommitted})
	if err != nil {
		return false, fmt.Errorf("store.MarkAdUnlocked begin: %w", err)
	}
	committed := false
	defer func() {
		if !committed {
			_ = tx.Rollback()
		}
	}()

	var unlockedAt sql.NullTime
	row := tx.QueryRowContext(ctx,
		`SELECT ad_unlocked_at FROM usage_daily WHERE user_id = ? AND date = ? `+s.dialect.LockForUpdate(),
		userID, d)
	switch err := row.Scan(&unlockedAt); err {
	case nil:
		if unlockedAt.Valid {
			// Already unlocked today → idempotent success.
			if cErr := tx.Commit(); cErr != nil {
				return false, fmt.Errorf("store.MarkAdUnlocked commit: %w", cErr)
			}
			committed = true
			return true, nil
		}
		if _, uErr := tx.ExecContext(ctx,
			`UPDATE usage_daily SET ad_unlocked_at = ?
			 WHERE user_id = ? AND date = ? AND ad_unlocked_at IS NULL`,
			now, userID, d); uErr != nil {
			return false, fmt.Errorf("store.MarkAdUnlocked update: %w", uErr)
		}
	case sql.ErrNoRows:
		if _, iErr := tx.ExecContext(ctx,
			`INSERT INTO usage_daily (user_id, date, ad_unlocked_at)
			 VALUES (?, ?, ?)`,
			userID, d, now); iErr != nil {
			return false, fmt.Errorf("store.MarkAdUnlocked insert: %w", iErr)
		}
	default:
		return false, fmt.Errorf("store.MarkAdUnlocked select: %w", err)
	}

	if cErr := tx.Commit(); cErr != nil {
		return false, fmt.Errorf("store.MarkAdUnlocked commit: %w", cErr)
	}
	committed = true
	return false, nil
}

// EffectivePlan returns the plan that currently governs userID: the highest
// tier among the user's non-expired subscriptions, falling back to the free
// plan when the user has no active subscription (trial-expired free state).
func (s *Store) EffectivePlan(ctx context.Context, userID int64) (*Plan, error) {
	var p Plan
	err := s.db.QueryRowContext(ctx,
		`SELECT p.code, p.daily_minutes, p.ad_gate
		 FROM subscriptions s
		 JOIN plans p ON p.id = s.plan_id
		 WHERE s.user_id = ? AND s.expires_at > ?
		 ORDER BY CASE p.code WHEN 'team' THEN 0 WHEN 'pro' THEN 1 WHEN 'free' THEN 2 ELSE 3 END,
		          s.expires_at DESC
		 LIMIT 1`,
		userID, time.Now().UTC()).Scan(&p.Code, &p.DailyMinutes, &p.AdGate)
	if err == nil {
		return &p, nil
	}
	if err != sql.ErrNoRows {
		return nil, fmt.Errorf("store.EffectivePlan: %w", err)
	}

	// No active subscription → free plan.
	if err := s.db.QueryRowContext(ctx,
		`SELECT code, daily_minutes, ad_gate FROM plans WHERE code = 'free'`).
		Scan(&p.Code, &p.DailyMinutes, &p.AdGate); err != nil {
		return nil, fmt.Errorf("store.EffectivePlan free fallback: %w", err)
	}
	return &p, nil
}