package tasks

import (
	"context"
	"database/sql"
	"errors"
	"strings"
	"time"

	"cmbuyer/admin/internal/domain"
)

// ErrInvalidFilter 表示任务筛选值无效，路由应按字段重新渲染而不是泄露内部错误。
var ErrInvalidFilter = errors.New("invalid task filter")

// SetStartPolicy is called during startup; policy is explicit because authorization limits must not be implicit defaults.
func (store *SQLiteStore) SetStartPolicy(policy StartPolicy) { store.policy = policy }

func (store *SQLiteStore) ListTasks(ctx context.Context, filter TaskFilter) ([]TaskRow, error) {
	if !ValidateTaskFilter(filter).Valid() {
		return nil, ErrInvalidFilter
	}
	from, to, err := ShanghaiRange(filter.CreatedFrom, filter.CreatedTo)
	if err != nil {
		return nil, ErrInvalidFilter
	}
	clauses, args := []string{"1=1"}, []any{}
	if filter.Status != "" {
		clauses = append(clauses, "status = ?")
		args = append(args, filter.Status)
	}
	if filter.Keyword != "" {
		escaped := strings.NewReplacer("\\", "\\\\", "%", "\\%", "_", "\\_").Replace(filter.Keyword)
		clauses = append(clauses, "(title LIKE ? ESCAPE '\\' OR goods_id LIKE ? ESCAPE '\\')")
		args = append(args, "%"+escaped+"%", "%"+escaped+"%")
	}
	if !from.IsZero() {
		clauses = append(clauses, "julianday(created_at) >= julianday(?)")
		args = append(args, from.Format(time.RFC3339Nano))
	}
	if !to.IsZero() {
		clauses = append(clauses, "julianday(created_at) < julianday(?)")
		args = append(args, to.Format(time.RFC3339Nano))
	}
	rows, err := store.database.QueryContext(ctx, "SELECT id,title,goods_id,sku_color,sku_size,quantity,max_total_price,status,version,created_at FROM tasks WHERE "+strings.Join(clauses, " AND ")+" ORDER BY julianday(created_at) DESC,rowid DESC", args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	result := []TaskRow{}
	for rows.Next() {
		var item TaskRow
		var created string
		if err := rows.Scan(&item.ID, &item.Title, &item.GoodsID, &item.SKUColor, &item.SKUSize, &item.Quantity, &item.MaxTotalPrice, &item.Status, &item.Version, &created); err != nil {
			return nil, err
		}
		item.CreatedAt, err = time.Parse(time.RFC3339Nano, created)
		if err != nil {
			return nil, err
		}
		result = append(result, item)
	}
	return result, rows.Err()
}

// ValidateTaskFilter 返回可关联到字段的错误，使服务端页面拒绝篡改参数时仍能保留输入值。
func ValidateTaskFilter(filter TaskFilter) Errors {
	validation := Errors{}
	if !validTaskStatus(filter.Status) {
		validation["status"] = "请选择有效的任务状态。"
	}
	location, err := time.LoadLocation("Asia/Shanghai")
	if err != nil {
		validation["created_from"] = "日期筛选暂不可用，请稍后重试。"
		validation["created_to"] = "日期筛选暂不可用，请稍后重试。"
		return validation
	}
	parseDate := func(field, value string) (time.Time, bool) {
		if value == "" {
			return time.Time{}, true
		}
		parsed, parseErr := time.ParseInLocation("2006-01-02", value, location)
		if parseErr != nil {
			validation[field] = "请输入有效日期。"
			return time.Time{}, false
		}
		return parsed, true
	}
	from, fromOK := parseDate("created_from", filter.CreatedFrom)
	to, toOK := parseDate("created_to", filter.CreatedTo)
	if fromOK && toOK && !from.IsZero() && !to.IsZero() && from.After(to) {
		validation["created_to"] = "结束日期不能早于开始日期。"
	}
	return validation
}

func (store *SQLiteStore) StartPurchases(ctx context.Context, command StartCommand, createdBy string) (StartResult, error) {
	items, err := startItems(command)
	if err != nil || createdBy == "" {
		return StartResult{}, ErrInvalidStart
	}
	if store.policy.AuthorizationTTL <= 0 || store.policy.MaxQuantity <= 0 {
		return StartResult{}, ErrInvalidStart
	}
	_, ceiling, ok := normalizeCents(store.policy.MaxTotalPrice)
	if !ok {
		return StartResult{}, ErrInvalidStart
	}
	writeCtx, cancel := context.WithTimeout(ctx, sqliteWriteTimeout)
	defer cancel()
	select {
	case store.writeGate <- struct{}{}:
		defer func() { <-store.writeGate }()
	case <-writeCtx.Done():
		return StartResult{}, writeCtx.Err()
	}
	tx, err := store.database.BeginTx(writeCtx, nil)
	if err != nil {
		return StartResult{}, err
	}
	defer tx.Rollback()
	// Replay precedes any DRAFT check. One service process serializes this check with creation; SQLite uniqueness remains the cross-transaction backstop.
	result, found, err := replayStart(writeCtx, tx, command.StartKey, items)
	if err != nil {
		return StartResult{}, err
	}
	if found {
		if err := tx.Commit(); err != nil {
			return StartResult{}, err
		}
		return result, nil
	}
	now := store.now().UTC()
	expires := now.Add(store.policy.AuthorizationTTL)
	result = StartResult{StartKey: command.StartKey, AuthorizedCount: len(items), Tasks: make([]AuthorizedTask, 0, len(items)), PaymentAutomated: false}
	for _, item := range items {
		var title, goods, color, size, price, status string
		var quantity, version int
		if err := tx.QueryRowContext(writeCtx, "SELECT title,goods_id,sku_color,sku_size,quantity,max_total_price,status,version FROM tasks WHERE id=?", item.TaskID).Scan(&title, &goods, &color, &size, &quantity, &price, &status, &version); err != nil {
			if err == sql.ErrNoRows {
				return StartResult{}, ErrStartConflict
			}
			return StartResult{}, err
		}
		if status != "DRAFT" || version != item.ExpectedTaskVersion ||
			!ValidTaskWireFields(title, goods, color, size, price) ||
			quantity < 1 || quantity > store.policy.MaxQuantity {
			return StartResult{}, ErrStartConflict
		}
		canonical, cents, ok := normalizeCents(price)
		if !ok || canonical != price || cents.Cmp(ceiling) > 0 {
			return StartResult{}, ErrStartConflict
		}
		if _, err := domain.TransitionTask(domain.TaskStatusDraft, domain.TaskStatusPending); err != nil {
			return StartResult{}, err
		}
		id, err := NewCreateKey()
		if err != nil {
			return StartResult{}, err
		}
		next := version + 1
		if _, err = tx.ExecContext(writeCtx, "INSERT INTO order_authorizations (id,task_id,task_version,start_key,goods_id,sku_color,sku_size,quantity,total_price_cap,status,created_by,created_at,expires_at) VALUES (?,?,?,?,?,?,?,?,?,'ACTIVE',?,?,?)", id, item.TaskID, next, command.StartKey, goods, color, size, quantity, price, createdBy, now.Format(time.RFC3339Nano), expires.Format(time.RFC3339Nano)); err != nil {
			return StartResult{}, err
		}
		updated, err := tx.ExecContext(writeCtx, "UPDATE tasks SET status='PENDING',version=version+1,updated_at=? WHERE id=? AND status='DRAFT' AND version=?", now.Format(time.RFC3339Nano), item.TaskID, version)
		if err != nil {
			return StartResult{}, err
		}
		affected, err := updated.RowsAffected()
		if err != nil {
			return StartResult{}, err
		}
		if affected != 1 {
			return StartResult{}, ErrStartConflict
		}
		result.Tasks = append(result.Tasks, AuthorizedTask{TaskID: item.TaskID, TaskVersion: next, AuthorizationID: id, ExpiresAt: expires})
	}
	if err := tx.Commit(); err != nil {
		return StartResult{}, err
	}
	return result, nil
}

func replayStart(ctx context.Context, tx *sql.Tx, startKey string, items []StartItem) (StartResult, bool, error) {
	rows, err := tx.QueryContext(ctx, `SELECT authorizations.id,authorizations.task_id,
		authorizations.task_version,authorizations.expires_at,authorizations.goods_id,
		authorizations.sku_color,authorizations.sku_size,authorizations.quantity,
		authorizations.total_price_cap,tasks.title,tasks.goods_id,tasks.sku_color,
		tasks.sku_size,tasks.quantity,tasks.max_total_price
		FROM order_authorizations AS authorizations
		JOIN tasks ON tasks.id = authorizations.task_id
		WHERE authorizations.start_key=? ORDER BY authorizations.task_id`, startKey)
	if err != nil {
		return StartResult{}, false, err
	}
	defer rows.Close()
	result := StartResult{StartKey: startKey, PaymentAutomated: false}
	for rows.Next() {
		var item AuthorizedTask
		var expires string
		var authorizationGoodsID, authorizationColor, authorizationSize, authorizationPrice string
		var taskTitle, taskGoodsID, taskColor, taskSize, taskPrice string
		var authorizationQuantity, taskQuantity int
		if err := rows.Scan(&item.AuthorizationID, &item.TaskID, &item.TaskVersion, &expires,
			&authorizationGoodsID, &authorizationColor, &authorizationSize, &authorizationQuantity,
			&authorizationPrice, &taskTitle, &taskGoodsID, &taskColor, &taskSize, &taskQuantity,
			&taskPrice); err != nil {
			return StartResult{}, false, err
		}
		if !ValidAuthorizationFields(authorizationGoodsID, authorizationColor, authorizationSize, authorizationPrice) ||
			authorizationQuantity <= 0 ||
			!ValidTaskWireFields(taskTitle, taskGoodsID, taskColor, taskSize, taskPrice) || taskQuantity <= 0 ||
			authorizationGoodsID != taskGoodsID || authorizationColor != taskColor ||
			authorizationSize != taskSize || authorizationQuantity != taskQuantity || authorizationPrice != taskPrice {
			return StartResult{}, false, ErrStartConflict
		}
		item.ExpiresAt, err = time.Parse(time.RFC3339Nano, expires)
		if err != nil {
			return StartResult{}, false, err
		}
		result.Tasks = append(result.Tasks, item)
	}
	if err := rows.Err(); err != nil {
		return StartResult{}, false, err
	}
	if len(result.Tasks) == 0 {
		return StartResult{}, false, nil
	}
	if len(result.Tasks) != len(items) {
		return StartResult{}, false, ErrStartConflict
	}
	for i := range items {
		if result.Tasks[i].TaskID != items[i].TaskID || result.Tasks[i].TaskVersion-1 != items[i].ExpectedTaskVersion {
			return StartResult{}, false, ErrStartConflict
		}
	}
	result.AuthorizedCount = len(result.Tasks)
	return result, true, nil
}