package validator

import (
	"fmt"
	"sync"

	"github.com/google/cel-go/cel"
	"github.com/google/cel-go/common/types"
	"github.com/google/cel-go/common/types/ref"
	"google.golang.org/protobuf/proto"
)

// CELExecutor CEL 表达式执行器
type CELExecutor struct {
	mu    sync.RWMutex
	cache map[string]cel.Program // 表达式缓存 (cel.Program 是接口,不需要指针)
	env   *cel.Env               // CEL 环境
}

// NewCELExecutor 创建 CEL 执行器
func NewCELExecutor() (*CELExecutor, error) {
	// 创建 CEL 环境 (v0.26+ 不需要显式注册基础类型)
	env, err := cel.NewEnv()
	if err != nil {
		return nil, fmt.Errorf("failed to create CEL environment: %w", err)
	}

	return &CELExecutor{
		cache: make(map[string]cel.Program),
		env:   env,
	}, nil
}

// Evaluate 执行 CEL 表达式
func (e *CELExecutor) Evaluate(expression string, data map[string]interface{}) (bool, error) {
	// 获取或编译程序
	prog, err := e.getProgram(expression)
	if err != nil {
		return false, fmt.Errorf("failed to compile CEL expression: %w", err)
	}

	// 执行表达式
	result, _, err := prog.Eval(data)
	if err != nil {
		return false, fmt.Errorf("failed to evaluate CEL expression: %w", err)
	}

	// 检查结果类型
	boolResult, ok := result.Value().(bool)
	if !ok {
		return false, fmt.Errorf("CEL expression must return boolean, got %T", result.Value())
	}

	return boolResult, nil
}

// EvaluateWithProto 使用 Proto 消息执行 CEL 表达式
func (e *CELExecutor) EvaluateWithProto(expression string, msg proto.Message) (bool, error) {
	// 获取或编译程序
	prog, err := e.getProgram(expression)
	if err != nil {
		return false, fmt.Errorf("failed to compile CEL expression: %w", err)
	}

	// 将 Proto 消息转换为 CEL 变量
	data := map[string]interface{}{
		"this": msg,
	}

	// 执行表达式
	result, _, err := prog.Eval(data)
	if err != nil {
		return false, fmt.Errorf("failed to evaluate CEL expression: %w", err)
	}

	// 检查结果类型
	boolResult, ok := result.Value().(bool)
	if !ok {
		return false, fmt.Errorf("CEL expression must return boolean, got %T", result.Value())
	}

	return boolResult, nil
}

// EvaluateFieldRule 执行字段级 CEL 规则
func (e *CELExecutor) EvaluateFieldRule(expression string, fieldValue interface{}, parent proto.Message) (bool, error) {
	// 获取或编译程序
	prog, err := e.getProgram(expression)
	if err != nil {
		return false, fmt.Errorf("failed to compile CEL expression: %w", err)
	}

	// 准备数据
	data := map[string]interface{}{
		"this": fieldValue,
	}

	// 如果有父消息,也添加进去(用于跨字段验证)
	if parent != nil {
		data["parent"] = parent
	}

	// 执行表达式
	result, _, err := prog.Eval(data)
	if err != nil {
		return false, fmt.Errorf("failed to evaluate CEL expression: %w", err)
	}

	// 检查结果类型
	boolResult, ok := result.Value().(bool)
	if !ok {
		return false, fmt.Errorf("CEL expression must return boolean, got %T", result.Value())
	}

	return boolResult, nil
}

// EvaluateString 执行返回字符串的 CEL 表达式(用于动态错误消息)
func (e *CELExecutor) EvaluateString(expression string, data map[string]interface{}) (string, error) {
	// 获取或编译程序
	prog, err := e.getProgram(expression)
	if err != nil {
		return "", fmt.Errorf("failed to compile CEL expression: %w", err)
	}

	// 执行表达式
	result, _, err := prog.Eval(data)
	if err != nil {
		return "", fmt.Errorf("failed to evaluate CEL expression: %w", err)
	}

	// 检查结果类型
	strResult, ok := result.Value().(string)
	if !ok {
		return "", fmt.Errorf("CEL expression must return string, got %T", result.Value())
	}

	return strResult, nil
}

// getProgram 获取或编译程序(带缓存)
func (e *CELExecutor) getProgram(expression string) (cel.Program, error) {
	// 先尝试从缓存读取
	e.mu.RLock()
	if prog, ok := e.cache[expression]; ok {
		e.mu.RUnlock()
		return prog, nil
	}
	e.mu.RUnlock()

	// 编译表达式
	ast, issues := e.env.Compile(expression)
	if issues != nil && issues.Err() != nil {
		return nil, fmt.Errorf("CEL compilation error: %w", issues.Err())
	}

	// 创建程序
	prog, err := e.env.Program(ast)
	if err != nil {
		return nil, fmt.Errorf("failed to create CEL program: %w", err)
	}

	// 存入缓存
	e.mu.Lock()
	e.cache[expression] = prog
	e.mu.Unlock()

	return prog, nil
}

// ClearCache 清空表达式缓存
func (e *CELExecutor) ClearCache() {
	e.mu.Lock()
	e.cache = make(map[string]cel.Program)
	e.mu.Unlock()
}

// CacheSize 获取缓存大小
func (e *CELExecutor) CacheSize() int {
	e.mu.RLock()
	defer e.mu.RUnlock()
	return len(e.cache)
}

// ValidateCELExpression 验证 CEL 表达式语法(不执行)
func (e *CELExecutor) ValidateCELExpression(expression string) error {
	_, issues := e.env.Compile(expression)
	if issues != nil && issues.Err() != nil {
		return fmt.Errorf("invalid CEL expression: %w", issues.Err())
	}
	return nil
}

// Helper 函数

// celBool 将 ref.Val 转换为 bool
func celBool(val ref.Val) (bool, bool) {
	if val.Type() == types.BoolType {
		return val.Value().(bool), true
	}
	return false, false
}

// celString 将 ref.Val 转换为 string
func celString(val ref.Val) (string, bool) {
	if val.Type() == types.StringType {
		return val.Value().(string), true
	}
	return "", false
}

// celInt 将 ref.Val 转换为 int64
func celInt(val ref.Val) (int64, bool) {
	if val.Type() == types.IntType {
		return val.Value().(int64), true
	}
	return 0, false
}

// celDouble 将 ref.Val 转换为 float64
func celDouble(val ref.Val) (float64, bool) {
	if val.Type() == types.DoubleType {
		return val.Value().(float64), true
	}
	return 0, false
}