// Package common 提供平台资源可复用的配置化模糊搜索能力。
// 版本：v1.0.0
package common

import (
	"reflect"
	"strings"
	"sync"

	"github.com/gin-gonic/gin"
)

const configuredKeywordSearchContextKey = "configured_keyword_search"

// KeywordSearchKind 描述搜索字段的匹配方式。
type KeywordSearchKind string

const (
	// KeywordSearchText 按数据库原始文本执行不区分大小写的包含匹配。
	KeywordSearchText KeywordSearchKind = "text"
	// KeywordSearchEnum 仅按页面展示的中文枚举名称匹配，不暴露内部英文编码。
	KeywordSearchEnum KeywordSearchKind = "enum"
)

// KeywordSearchValue 描述枚举搜索中的可信编码与页面中文名称。
type KeywordSearchValue struct {
	Value string `json:"value"`
	Label string `json:"label"`
}

// KeywordSearchField 描述一个资源允许搜索的可见字段。
type KeywordSearchField struct {
	Key    string               `json:"key"`
	Kind   KeywordSearchKind    `json:"kind"`
	Values []KeywordSearchValue `json:"values,omitempty"`
}

var configuredKeywordPolicies = struct {
	sync.RWMutex
	fields map[reflect.Type][]KeywordSearchField
}{fields: make(map[reflect.Type][]KeywordSearchField)}

// EnableConfiguredKeywordSearch 标记当前路由使用资源级搜索配置。
// 返回值：Gin 中间件，仅影响挂载该中间件的平台总后台路由。
func EnableConfiguredKeywordSearch() gin.HandlerFunc {
	return func(ctx *gin.Context) {
		ctx.Set(configuredKeywordSearchContextKey, true)
		ctx.Next()
	}
}

// RegisterKeywordSearchPolicy 注册模型的搜索字段，并在启动阶段拒绝不安全配置。
// 参数：model 必须为模型结构体指针；fields 只能引用安全白名单中的直接字符串列。
func RegisterKeywordSearchPolicy(model any, fields []KeywordSearchField) {
	modelType := indirectModelType(model)
	validated := make([]KeywordSearchField, 0, len(fields))
	for _, field := range fields {
		validateKeywordSearchField(model, modelType, field)
		validated = append(validated, cloneKeywordSearchField(field))
	}
	configuredKeywordPolicies.Lock()
	defer configuredKeywordPolicies.Unlock()
	if _, exists := configuredKeywordPolicies.fields[modelType]; exists {
		panic("重复注册资源搜索策略：" + modelType.String())
	}
	configuredKeywordPolicies.fields[modelType] = validated
}

// ConfiguredKeywordSearchFields 返回模型的只读搜索契约副本。
func ConfiguredKeywordSearchFields(model any) []KeywordSearchField {
	modelType := indirectModelType(model)
	configuredKeywordPolicies.RLock()
	defer configuredKeywordPolicies.RUnlock()
	fields := configuredKeywordPolicies.fields[modelType]
	result := make([]KeywordSearchField, 0, len(fields))
	for _, field := range fields {
		result = append(result, cloneKeywordSearchField(field))
	}
	return result
}

func useConfiguredKeywordSearch(ctx *gin.Context) bool {
	enabled, exists := ctx.Get(configuredKeywordSearchContextKey)
	return exists && enabled == true
}

// configuredKeywordConditions 将用户关键字编译为参数化 SQL 条件。
// 枚举字段只接受中文展示名称，普通文本字段保持原有包含匹配行为。
func configuredKeywordConditions(model any, keyword string) ([]string, []any) {
	fields := ConfiguredKeywordSearchFields(model)
	conditions := make([]string, 0, len(fields))
	arguments := make([]any, 0, len(fields))
	for _, field := range fields {
		switch field.Kind {
		case KeywordSearchText:
			conditions = append(conditions, `LOWER("`+field.Key+`") LIKE ?`)
			arguments = append(arguments, "%"+keyword+"%")
		case KeywordSearchEnum:
			values := matchingKeywordEnumValues(field.Values, keyword)
			if len(values) == 0 {
				continue
			}
			placeholders := strings.TrimRight(strings.Repeat("?,", len(values)), ",")
			conditions = append(conditions, `"`+field.Key+`" IN (`+placeholders+")")
			for _, value := range values {
				arguments = append(arguments, value)
			}
		}
	}
	return conditions, arguments
}

func matchingKeywordEnumValues(values []KeywordSearchValue, keyword string) []string {
	matched := make([]string, 0, len(values))
	for _, value := range values {
		if strings.Contains(strings.ToLower(value.Label), keyword) {
			matched = append(matched, value.Value)
		}
	}
	return matched
}

func validateKeywordSearchField(model any, modelType reflect.Type, field KeywordSearchField) {
	if !keywordSafeColumns[field.Key] || isSensitiveKeywordColumn(model, field.Key) {
		panic("资源搜索字段不在安全白名单中：" + modelType.String() + "." + field.Key)
	}
	if !hasDirectStringColumn(modelType, field.Key) {
		panic("资源搜索字段不是模型直接字符串列：" + modelType.String() + "." + field.Key)
	}
	if field.Kind != KeywordSearchText && field.Kind != KeywordSearchEnum {
		panic("资源搜索字段类型无效：" + string(field.Kind))
	}
	if field.Kind == KeywordSearchEnum && len(field.Values) == 0 {
		panic("枚举搜索字段缺少中文值：" + modelType.String() + "." + field.Key)
	}
}

func hasDirectStringColumn(modelType reflect.Type, column string) bool {
	for index := 0; index < modelType.NumField(); index++ {
		field := modelType.Field(index)
		if !field.Anonymous && field.Type.Kind() == reflect.String && gormColumn(field.Tag.Get("gorm")) == column {
			return true
		}
	}
	return false
}

func indirectModelType(model any) reflect.Type {
	modelType := reflect.TypeOf(model)
	for modelType.Kind() == reflect.Pointer {
		modelType = modelType.Elem()
	}
	if modelType.Kind() != reflect.Struct {
		panic("资源搜索模型必须为结构体或结构体指针")
	}
	return modelType
}

func cloneKeywordSearchField(field KeywordSearchField) KeywordSearchField {
	clone := field
	clone.Values = append([]KeywordSearchValue(nil), field.Values...)
	return clone
}