package common

import (
	"fmt"
	"strings"

	"server/config"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// InitTenantPlugin 初始化租户插件
func InitTenantPlugin(db *gorm.DB) {
	if db == nil {
		return
	}
	plugin := NewTenantPlugin(config.AppConfig.Tenant)
	if err := db.Use(plugin); err != nil {
		LogError("租户插件初始化失败: %v", err)
		return
	}
	Info("租户插件初始化完成 (enable=%v)", plugin.enabled)
}

// TenantPlugin GORM 多租户插件
type TenantPlugin struct {
	enabled  bool
	column   string
	tableSet map[string]struct{}
	applyAll bool
}

// NewTenantPlugin 创建插件实例
func NewTenantPlugin(cfg config.TenantConfig) *TenantPlugin {
	column := strings.TrimSpace(cfg.Column)
	if column == "" {
		column = "tenant_id"
	}
	tableSet := make(map[string]struct{})
	applyAll := false
	for _, table := range cfg.Tables {
		name := normalizeTableName(table)
		if name == "" {
			continue
		}
		if name == "*" {
			applyAll = true
			continue
		}
		tableSet[name] = struct{}{}
	}
	return &TenantPlugin{
		enabled:  cfg.Enable,
		column:   column,
		tableSet: tableSet,
		applyAll: applyAll,
	}
}

// Name 插件名
func (p *TenantPlugin) Name() string {
	return "tenant_plugin"
}

// Initialize 注册回调
func (p *TenantPlugin) Initialize(db *gorm.DB) error {
	db.Callback().Query().Before("gorm:query").Register("tenant:query", p.before)
	db.Callback().Row().Before("gorm:row").Register("tenant:row", p.before)
	db.Callback().Raw().Before("gorm:raw").Register("tenant:raw", p.before)
	db.Callback().Update().Before("gorm:update").Register("tenant:update", p.before)
	db.Callback().Delete().Before("gorm:delete").Register("tenant:delete", p.before)
	return nil
}

func (p *TenantPlugin) before(db *gorm.DB) {
	if !p.enabled || db == nil || db.Statement == nil {
		return
	}
	if skip, ok := db.Get(DBSettingTenantSkip); ok {
		if v, ok := skip.(bool); ok && v {
			return
		}
	}

	tenantID, ok := p.tenantID(db)
	if !ok {
		return
	}

	table := p.tableName(db)
	if table == "" || !p.matchTable(table) {
		return
	}

	db.Statement.AddClause(clause.Where{
		Exprs: []clause.Expression{
			clause.Eq{
				Column: clause.Column{Name: p.column},
				Value:  tenantID,
			},
		},
	})
}

func (p *TenantPlugin) tenantID(db *gorm.DB) (string, bool) {
	if db == nil {
		return "", false
	}
	if value, ok := db.Get(DBSettingTenantID); ok {
		id := strings.TrimSpace(fmt.Sprint(value))
		if id != "" {
			return id, true
		}
	}
	if db.Statement != nil && db.Statement.Context != nil {
		id := TenantIDFromContext(db.Statement.Context)
		if id != "" {
			return id, true
		}
	}
	return "", false
}

func (p *TenantPlugin) tableName(db *gorm.DB) string {
	if db == nil || db.Statement == nil {
		return ""
	}
	if db.Statement.Schema != nil && db.Statement.Schema.Table != "" {
		return normalizeTableName(db.Statement.Schema.Table)
	}
	if db.Statement.Table != "" {
		return normalizeTableName(db.Statement.Table)
	}
	if db.Statement.SQL.String() != "" {
		return normalizeTableName(tableFromSQL(db.Statement.SQL.String()))
	}
	return ""
}

func (p *TenantPlugin) matchTable(table string) bool {
	if p.applyAll {
		return true
	}
	_, ok := p.tableSet[normalizeTableName(table)]
	return ok
}

func normalizeTableName(name string) string {
	name = strings.TrimSpace(name)
	if name == "" {
		return ""
	}
	fields := strings.Fields(name)
	if len(fields) > 0 {
		name = fields[0]
	}
	name = strings.Trim(name, "`\"")
	if idx := strings.LastIndex(name, "."); idx >= 0 {
		name = name[idx+1:]
	}
	return strings.ToLower(strings.TrimSpace(name))
}

func tableFromSQL(sql string) string {
	lower := strings.ToLower(sql)
	idx := strings.Index(lower, " from ")
	if idx == -1 {
		return ""
	}
	rest := strings.TrimSpace(sql[idx+6:])
	if rest == "" {
		return ""
	}
	fields := strings.Fields(rest)
	if len(fields) == 0 {
		return ""
	}
	table := strings.Trim(fields[0], "`\"")
	if strings.HasPrefix(table, "(") {
		return ""
	}
	return table
}