package codes

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

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

// PlanCode represents a plan tier.
type PlanCode string

const (
	PlanFree PlanCode = "free"
	PlanPro  PlanCode = "pro"
	PlanTeam PlanCode = "team"
)

// planTier returns a numeric tier for comparison (higher = better).
func planTier(p PlanCode) int {
	switch p {
	case PlanTeam:
		return 3
	case PlanPro:
		return 2
	default:
		return 1
	}
}

// BatchChannel is the source channel for a code batch.
type BatchChannel string

const (
	ChannelStore  BatchChannel = "store"
	ChannelTG     BatchChannel = "tg"
	ChannelLine   BatchChannel = "line"
	ChannelManual BatchChannel = "manual"
)

// SubscriptionRow mirrors the `subscriptions` DB row.
type SubscriptionRow struct {
	ID        int64
	UserID    int64
	PlanID    int64
	PlanCode  PlanCode
	ExpiresAt time.Time
	Source    string
}

// Store wraps a *sql.DB and exposes all database operations needed by the
// codes package.  Every method that modifies data is safe to call inside or
// outside an explicit transaction; methods that accept a *sql.Tx run within
// that transaction.
type Store struct {
	db      *sql.DB
	dialect dbx.Dialect
	lib     *libcodes.Store
}

// NewStore creates a Store backed by the given connection pool (MySQL or SQLite).
func NewStore(db *sql.DB) *Store {
	d := dbx.DialectForDB(db)
	libD := libcodes.DialectMySQL
	if d.Name() == "sqlite" {
		libD = libcodes.DialectSQLite
	}
	return &Store{db: db, dialect: d, lib: libcodes.NewStore(db, libD)}
}

// Lib exposes the shared library store (used by Service / webhook shim).
func (s *Store) Lib() *libcodes.Store { return s.lib }

// --------------------------------------------------------------------------
// Subscription helpers (used inside redeem transaction)
// --------------------------------------------------------------------------

// GetPlanID returns the primary key of plans.code.
func (s *Store) GetPlanID(ctx context.Context, code PlanCode) (int64, error) {
	var id int64
	err := s.db.QueryRowContext(ctx, `SELECT id FROM plans WHERE code=?`, string(code)).Scan(&id)
	if err != nil {
		return 0, fmt.Errorf("store.GetPlanID(%s): %w", code, err)
	}
	return id, nil
}

// GetPlanIDTx is GetPlanID inside a transaction (grant callback runs inside
// the redeem tx and must not touch the pool).
func (s *Store) GetPlanIDTx(ctx context.Context, tx *sql.Tx, code PlanCode) (int64, error) {
	var id int64
	if err := tx.QueryRowContext(ctx, `SELECT id FROM plans WHERE code=?`, string(code)).Scan(&id); err != nil {
		return 0, fmt.Errorf("store.GetPlanIDTx(%s): %w", code, err)
	}
	return id, nil
}

// GetActiveSubscriptions returns all non-expired subscriptions for userID,
// ordered by expires_at DESC.  Called inside the redeem transaction.
func (s *Store) GetActiveSubscriptions(ctx context.Context, tx *sql.Tx, userID int64) ([]SubscriptionRow, error) {
	rows, err := tx.QueryContext(ctx,
		`SELECT s.id, s.user_id, s.plan_id, p.code, s.expires_at, s.source
		 FROM subscriptions s
		 JOIN plans p ON p.id = s.plan_id
		 WHERE s.user_id=? AND s.expires_at > ?
		 ORDER BY s.expires_at DESC`,
		userID, time.Now().UTC())
	if err != nil {
		return nil, fmt.Errorf("store.GetActiveSubscriptions: %w", err)
	}
	defer rows.Close()

	var subs []SubscriptionRow
	for rows.Next() {
		var sr SubscriptionRow
		if err := rows.Scan(&sr.ID, &sr.UserID, &sr.PlanID, &sr.PlanCode, &sr.ExpiresAt, &sr.Source); err != nil {
			return nil, fmt.Errorf("store.GetActiveSubscriptions scan: %w", err)
		}
		subs = append(subs, sr)
	}
	return subs, rows.Err()
}

// ExtendSubscription sets expires_at to max(current_expires_at, now) + duration.
// Called inside the redeem transaction. The base date is computed in Go (the
// subscription row is read inside the locked redeem tx, then updated) — portable
// across engines and avoids DB-side DATE_ADD/GREATEST.
func (s *Store) ExtendSubscription(ctx context.Context, tx *sql.Tx, subID int64, durationDays int) error {
	var current time.Time
	if err := tx.QueryRowContext(ctx,
		`SELECT expires_at FROM subscriptions WHERE id=?`, subID).Scan(&current); err != nil {
		return fmt.Errorf("store.ExtendSubscription read: %w", err)
	}
	base := time.Now().UTC()
	if current.After(base) {
		base = current.UTC()
	}
	newExpiry := base.AddDate(0, 0, durationDays)

	_, err := tx.ExecContext(ctx,
		`UPDATE subscriptions SET expires_at = ? WHERE id=?`,
		newExpiry, subID)
	if err != nil {
		return fmt.Errorf("store.ExtendSubscription: %w", err)
	}
	return nil
}

// CreateSubscription inserts a new subscriptions row.  expires_at is set to
// max(now, latest_expires_at_for_same_plan) + duration_days.
// latestSamePlan may be zero-value if the user has no existing sub for that plan.
func (s *Store) CreateSubscription(
	ctx context.Context,
	tx *sql.Tx,
	userID, planID int64,
	durationDays int,
	latestSamePlan time.Time,
	source string,
) (int64, error) {
	now := time.Now().UTC()
	base := now
	if latestSamePlan.After(now) {
		base = latestSamePlan
	}
	expiresAt := base.AddDate(0, 0, durationDays)

	res, err := tx.ExecContext(ctx,
		`INSERT INTO subscriptions (user_id, plan_id, expires_at, source, created_at)
		 VALUES (?, ?, ?, ?, ?)`,
		userID, planID, expiresAt, source, now)
	if err != nil {
		return 0, fmt.Errorf("store.CreateSubscription: %w", err)
	}
	id, _ := res.LastInsertId()
	return id, nil
}

// --------------------------------------------------------------------------
// Audit log
// --------------------------------------------------------------------------

// WriteAuditLog inserts an audit_log row.  actor and target are string
// identifiers; meta is a JSON object (may be nil/empty).
func (s *Store) WriteAuditLog(ctx context.Context, tx *sql.Tx, actor, action, target, metaJSON string) error {
	var err error
	if metaJSON == "" {
		metaJSON = "null"
	}
	now := time.Now().UTC()
	if tx != nil {
		_, err = tx.ExecContext(ctx,
			`INSERT INTO audit_log (actor, action, target, meta, at) VALUES (?, ?, ?, ?, ?)`,
			actor, action, target, metaJSON, now)
	} else {
		_, err = s.db.ExecContext(ctx,
			`INSERT INTO audit_log (actor, action, target, meta, at) VALUES (?, ?, ?, ?, ?)`,
			actor, action, target, metaJSON, now)
	}
	if err != nil {
		return fmt.Errorf("store.WriteAuditLog: %w", err)
	}
	return nil
}

// --------------------------------------------------------------------------
// Webhook ingestion (single externally-generated code per call)
// --------------------------------------------------------------------------

// MintOne writes one externally-generated code (card-store webhook ingestion)
// as one batch + one code row in a single transaction. A duplicate code_hash
// returns ErrDuplicate with NOTHING committed — no orphan batch (the old
// two-statement implementation leaked one batch row per duplicate delivery).
func (s *Store) MintOne(ctx context.Context, codeHash string, ent libcodes.Entitlement, channel BatchChannel, createdBy, note string) error {
	tx, err := s.lib.BeginTx(ctx)
	if err != nil {
		return fmt.Errorf("store.MintOne: begin: %w", err)
	}
	defer tx.Rollback()

	batchID, err := s.lib.CreateBatchTx(ctx, tx, string(channel), ent, createdBy, note)
	if err != nil {
		return fmt.Errorf("store.MintOne: batch: %w", err)
	}
	if err := s.lib.CreateCodeTx(ctx, tx, codeHash, batchID, ent); err != nil {
		return err // ErrDuplicate passes through; defer 回滚保证无孤儿
	}
	if err := tx.Commit(); err != nil {
		return fmt.Errorf("store.MintOne: commit: %w", err)
	}
	return nil
}

// BeginTx starts a new transaction at Read Committed isolation level.
// The SELECT … FOR UPDATE in FindCodeByHashForUpdate provides the necessary
// row-level exclusivity; Serializable is intentionally avoided to reduce
// deadlock risk under concurrent redemptions.
func (s *Store) BeginTx(ctx context.Context) (*sql.Tx, error) {
	return s.db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelReadCommitted})
}