package repository

import (
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"strings"

	"cmautobuy/admin/model"
)

// ClientPurchaseMode 返回客户端最后一次登记时声明的采购能力。
// 旧数据、空值或无法解析的 JSON 一律按 dry_run 处理，这是安全默认值。
func ClientPurchaseMode(q Execer, clientID string) (string, error) {
	var raw sql.NullString
	if err := q.QueryRow(`SELECT capabilities FROM clients WHERE client_id = ?`, clientID).Scan(&raw); errors.Is(err, sql.ErrNoRows) {
		return "", ErrClientNotFound
	} else if err != nil {
		return "", fmt.Errorf("读取客户端 %s 的采购能力失败: %w", clientID, err)
	}
	return ParseClientPurchaseMode(raw.String), nil
}

// ParseClientPurchaseMode 把登记能力转成安全的固定值，供列表和创建校验共用。
func ParseClientPurchaseMode(raw string) string {
	var capabilities struct {
		PurchaseMode string `json:"purchase_mode"`
	}
	if json.Unmarshal([]byte(raw), &capabilities) == nil && capabilities.PurchaseMode == string(model.TaskExecutionLive) {
		return capabilities.PurchaseMode
	}
	return string(model.TaskExecutionDryRun)
}

var (
	ErrClientNotFound     = errors.New("客户端不存在")
	ErrPurchaserNotActive = errors.New("采购员不存在或已禁用")
	ErrClientNotAssigned  = errors.New("客户端当前未绑定采购员")
)

// ClientWithAssignee 是客户端列表查询结果。归属为空表示尚未绑定。
type ClientWithAssignee struct {
	model.Client
	AssignedUserID   string
	AssignedUsername string
}

// UpsertClient 登记或更新一台客户端。
//
// # 名称的更新规则（两个接口不一样，这是有意的）
//
//	explicit=true  用户在设置页点了"保存"，是**明确的人为操作**。
//	               带了非空名称就更新；名称为空则保留原有名称。
//	explicit=false claim 顺带做的隐式登记，是**后台自动调用**。
//	               永远不更新名称。
//
// 为什么区分：后台每次领取任务都上报一次名称，如果照单全收，
// 操作员在 Admin 界面精心改的名字会被客户端的默认值反复冲掉。
// 但用户明确点保存时，又应该能把新名字同步过去。
//
// 新建时名称为空则用 clientID 兜底，保证列表里不出现空白行。
func UpsertClient(q Execer, c model.Client, explicit bool) error {
	if c.ClientID == "" {
		return fmt.Errorf("client_id 不能为空")
	}

	name := strings.TrimSpace(c.Name)
	insertName := name
	if insertName == "" {
		insertName = c.ClientID // 新建时的兜底
	}
	// 只有"显式登记 + 名称非空"才允许覆盖已有名称
	updateName := explicit && name != ""

	now := model.NowISO()
	_, err := q.Exec(`
		INSERT INTO clients (client_id, name, device_address, platform,
		                     pdd_package, capabilities,
		                     last_seen_at, created_at, updated_at)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
		ON DUPLICATE KEY UPDATE
		    name           = CASE WHEN ? THEN ? ELSE clients.name END,
		    device_address = VALUES(device_address),
		    platform       = VALUES(platform),
		    pdd_package    = VALUES(pdd_package),
		    capabilities   = VALUES(capabilities),
		    last_seen_at   = VALUES(last_seen_at),
		    updated_at     = VALUES(updated_at)`,
		c.ClientID, insertName, c.DeviceAddress, c.Platform,
		c.PddPackage, c.Capabilities, now, now, now,
		updateName, name)
	if err != nil {
		return fmt.Errorf("登记客户端 %s 失败: %w", c.ClientID, err)
	}
	return nil
}

// TouchClient 只刷新 last_seen_at。
//
// claim / result / failure 三个接口都要调。只在 claim 里调的话，
// 客户端执行长任务期间不调 claim，会被误判成离线。
func TouchClient(q Execer, clientID string) error {
	now := model.NowISO()
	_, err := q.Exec(
		`UPDATE clients SET last_seen_at = ?, updated_at = ? WHERE client_id = ?`,
		now, now, clientID)
	if err != nil {
		return fmt.Errorf("刷新客户端 %s 活动时间失败: %w", clientID, err)
	}
	return nil
}

// ListClients 按名称模糊查询客户端，keyword 为空时返回全部。
func ListClients(db *sql.DB, keyword string) ([]model.Client, error) {
	query := `SELECT client_id, name, device_address, platform, pdd_package,
	                 capabilities, last_seen_at, created_at, updated_at
	          FROM clients`
	args := []any{}

	if kw := strings.TrimSpace(keyword); kw != "" {
		// 参数化查询，通配符拼在值里而不是 SQL 里
		query += ` WHERE name LIKE ? OR client_id LIKE ?`
		like := "%" + kw + "%"
		args = append(args, like, like)
	}
	query += ` ORDER BY last_seen_at DESC, client_id`

	rows, err := db.Query(query, args...)
	if err != nil {
		return nil, fmt.Errorf("查询客户端列表失败: %w", err)
	}
	defer rows.Close()

	var out []model.Client
	for rows.Next() {
		var c model.Client
		var name, addr, platform, pkg, caps sql.NullString
		if err := rows.Scan(&c.ClientID, &name, &addr, &platform, &pkg,
			&caps, &c.LastSeenAt, &c.CreatedAt, &c.UpdatedAt); err != nil {
			return nil, fmt.Errorf("读取客户端行失败: %w", err)
		}
		c.Name = name.String
		c.DeviceAddress = addr.String
		c.Platform = platform.String
		c.PddPackage = pkg.String
		c.Capabilities = caps.String
		out = append(out, c)
	}
	return out, rows.Err()
}

// clientListFilter 统一生成客户端分页、总数和在线统计的可见范围。
func clientListFilter(keyword, visibleUserID string) (string, []any) {
	where := make([]string, 0, 2)
	args := make([]any, 0, 3)
	if visibleUserID != "" {
		where = append(where, `a.user_id = ?`)
		args = append(args, visibleUserID)
	}
	if kw := strings.TrimSpace(keyword); kw != "" {
		where = append(where, `(c.name LIKE ? OR c.client_id LIKE ?)`)
		like := "%" + kw + "%"
		args = append(args, like, like)
	}
	if len(where) == 0 {
		return "", args
	}
	return ` WHERE ` + strings.Join(where, ` AND `), args
}

const clientListFrom = ` FROM clients c
		  LEFT JOIN client_user_assignments a
		    ON a.client_id = c.client_id AND a.ended_at IS NULL
		  LEFT JOIN users u ON u.user_id = a.user_id`

func listClientsForUserPage(db *sql.DB, keyword, visibleUserID string, limit, offset int) ([]ClientWithAssignee, error) {
	where, args := clientListFilter(keyword, visibleUserID)
	query := `SELECT c.client_id, c.name, c.device_address, c.platform, c.pdd_package,
	                 c.capabilities, c.last_seen_at, c.created_at, c.updated_at,
	                 a.user_id, u.username` + clientListFrom + where +
		` ORDER BY c.last_seen_at DESC, c.client_id`
	if limit >= 0 {
		query += ` LIMIT ? OFFSET ?`
		args = append(args, limit, offset)
	}

	rows, err := db.Query(query, args...)
	if err != nil {
		return nil, fmt.Errorf("查询客户端归属列表失败: %w", err)
	}
	defer rows.Close()
	out := make([]ClientWithAssignee, 0)
	for rows.Next() {
		var row ClientWithAssignee
		var name, addr, platform, pkg, caps, userID, username sql.NullString
		if err := rows.Scan(&row.ClientID, &name, &addr, &platform, &pkg, &caps,
			&row.LastSeenAt, &row.CreatedAt, &row.UpdatedAt, &userID, &username); err != nil {
			return nil, fmt.Errorf("读取客户端归属行失败: %w", err)
		}
		row.Name, row.DeviceAddress, row.Platform = name.String, addr.String, platform.String
		row.PddPackage, row.Capabilities = pkg.String, caps.String
		row.AssignedUserID, row.AssignedUsername = userID.String, username.String
		out = append(out, row)
	}
	return out, rows.Err()
}

// ListClientsForUser 返回带当前负责人的全部客户端，供需要完整候选集的业务使用。
func ListClientsForUser(db *sql.DB, keyword, visibleUserID string) ([]ClientWithAssignee, error) {
	return listClientsForUserPage(db, keyword, visibleUserID, -1, 0)
}

// ClientVisibleToUser 校验客户端是否存在且位于当前账号可见范围。
// visibleUserID 为空表示管理员，可选择任意已登记客户端。
func ClientVisibleToUser(q Execer, clientID, visibleUserID string) (bool, error) {
	query := `SELECT COUNT(*) FROM clients c`
	args := []any{}
	if visibleUserID != "" {
		query += ` JOIN client_user_assignments a
		             ON a.client_id = c.client_id AND a.ended_at IS NULL
		            AND a.user_id = ?`
		args = append(args, visibleUserID)
	}
	query += ` WHERE c.client_id = ?`
	args = append(args, clientID)
	var count int
	if err := q.QueryRow(query, args...).Scan(&count); err != nil {
		return false, fmt.Errorf("校验客户端可见范围失败: %w", err)
	}
	return count == 1, nil
}

// ListClientsForUserPage 返回一页客户端和同一可见范围内的总数。
func ListClientsForUserPage(db *sql.DB, keyword, visibleUserID string, limit, offset int) ([]ClientWithAssignee, int, error) {
	where, args := clientListFilter(keyword, visibleUserID)
	var total int
	if err := db.QueryRow(`SELECT COUNT(*)`+clientListFrom+where, args...).Scan(&total); err != nil {
		return nil, 0, fmt.Errorf("统计客户端列表失败: %w", err)
	}
	rows, err := listClientsForUserPage(db, keyword, visibleUserID, limit, offset)
	return rows, total, err
}

// CountOnlineClientsForUser 统计同一筛选和权限范围内的在线客户端。
// last_seen_at 统一以 UTC RFC3339 保存，固定宽度字符串的字典序就是时间顺序。
func CountOnlineClientsForUser(db *sql.DB, keyword, visibleUserID, cutoffISO string) (int, error) {
	where, args := clientListFilter(keyword, visibleUserID)
	args = append(args, cutoffISO)
	var online int
	query := `SELECT COUNT(*)` + clientListFrom + where
	if where == "" {
		query += ` WHERE c.last_seen_at > ?`
	} else {
		query += ` AND c.last_seen_at > ?`
	}
	if err := db.QueryRow(query, args...).Scan(&online); err != nil {
		return 0, fmt.Errorf("统计在线客户端失败: %w", err)
	}
	return online, nil
}

// ListActivePurchasers 返回可成为新负责人的启用采购员。
func ListActivePurchasers(db *sql.DB) ([]model.User, error) {
	rows, err := db.Query(`
		SELECT user_id, username, role, status, password_changed_at, created_at, updated_at
		  FROM users WHERE role = ? AND status = ? ORDER BY username`,
		model.RolePurchaser, model.UserActive)
	if err != nil {
		return nil, fmt.Errorf("查询可绑定采购员失败: %w", err)
	}
	defer rows.Close()
	users := make([]model.User, 0)
	for rows.Next() {
		var user model.User
		if err := rows.Scan(&user.UserID, &user.Username, &user.Role, &user.Status,
			&user.PasswordChangedAt, &user.CreatedAt, &user.UpdatedAt); err != nil {
			return nil, fmt.Errorf("读取可绑定采购员失败: %w", err)
		}
		users = append(users, user)
	}
	return users, rows.Err()
}

// AssignClient 原子完成首次绑定或转交。返回 changed、transferred。
func AssignClient(db *sql.DB, assignment model.ClientUserAssignment) (bool, bool, error) {
	tx, err := db.Begin()
	if err != nil {
		return false, false, fmt.Errorf("开始绑定客户端事务失败: %w", err)
	}
	defer tx.Rollback()
	var lockedClientID string
	if err := tx.QueryRow(`SELECT client_id FROM clients WHERE client_id = ? FOR UPDATE`, assignment.ClientID).Scan(&lockedClientID); errors.Is(err, sql.ErrNoRows) {
		return false, false, ErrClientNotFound
	} else if err != nil {
		return false, false, fmt.Errorf("检查客户端失败: %w", err)
	}
	var exists int
	if err := tx.QueryRow(`SELECT COUNT(*) FROM users WHERE user_id = ? AND role = ? AND status = ?`,
		assignment.UserID, model.RolePurchaser, model.UserActive).Scan(&exists); err != nil {
		return false, false, fmt.Errorf("检查采购员失败: %w", err)
	}
	if exists == 0 {
		return false, false, ErrPurchaserNotActive
	}

	var currentID, currentUserID string
	err = tx.QueryRow(`SELECT assignment_id, user_id FROM client_user_assignments
		WHERE client_id = ? AND ended_at IS NULL`, assignment.ClientID).Scan(&currentID, &currentUserID)
	if err != nil && !errors.Is(err, sql.ErrNoRows) {
		return false, false, fmt.Errorf("读取当前客户端归属失败: %w", err)
	}
	if err == nil && currentUserID == assignment.UserID {
		return false, false, nil
	}
	transferred := err == nil
	if transferred {
		if _, err := tx.Exec(`UPDATE client_user_assignments
			SET ended_at = ?, ended_by_user_id = ?, end_reason = 'transfer'
			WHERE assignment_id = ? AND ended_at IS NULL`,
			assignment.StartedAt, assignment.AssignedByUserID, currentID); err != nil {
			return false, false, fmt.Errorf("结束原客户端归属失败: %w", err)
		}
	}
	if _, err := tx.Exec(`INSERT INTO client_user_assignments
		(assignment_id, client_id, user_id, started_at, assigned_by_user_id)
		VALUES (?, ?, ?, ?, ?)`, assignment.AssignmentID, assignment.ClientID,
		assignment.UserID, assignment.StartedAt, assignment.AssignedByUserID); err != nil {
		return false, false, fmt.Errorf("保存客户端归属失败: %w", err)
	}
	if err := tx.Commit(); err != nil {
		return false, false, fmt.Errorf("提交客户端绑定事务失败: %w", err)
	}
	return true, transferred, nil
}

// UnassignClient 原子结束当前归属，历史记录保留。
func UnassignClient(db *sql.DB, clientID, actorUserID, endedAt string) error {
	tx, err := db.Begin()
	if err != nil {
		return fmt.Errorf("开始解绑客户端事务失败: %w", err)
	}
	defer tx.Rollback()
	res, err := tx.Exec(`UPDATE client_user_assignments
		SET ended_at = ?, ended_by_user_id = ?, end_reason = 'unbind'
		WHERE client_id = ? AND ended_at IS NULL`, endedAt, actorUserID, clientID)
	if err != nil {
		return fmt.Errorf("结束客户端归属失败: %w", err)
	}
	n, err := res.RowsAffected()
	if err != nil {
		return fmt.Errorf("读取解绑结果失败: %w", err)
	}
	if n == 0 {
		return ErrClientNotAssigned
	}
	if err := tx.Commit(); err != nil {
		return fmt.Errorf("提交客户端解绑事务失败: %w", err)
	}
	return nil
}

// DeleteClients 批量删除客户端。返回实际删除的条数。
func DeleteClients(db *sql.DB, clientIDs []string) (int64, error) {
	if len(clientIDs) == 0 {
		return 0, nil
	}

	// 占位符按数量生成，值仍然是参数化传入，不存在注入
	placeholders := strings.TrimSuffix(strings.Repeat("?,", len(clientIDs)), ",")
	args := make([]any, len(clientIDs))
	for i, id := range clientIDs {
		args[i] = id
	}

	res, err := db.Exec(
		`DELETE FROM clients WHERE client_id IN (`+placeholders+`)`, args...)
	if err != nil {
		return 0, fmt.Errorf("删除客户端失败: %w", err)
	}
	return res.RowsAffected()
}