package main

import (
	"fmt"
	"io"
	"net/http"
	"reflect"
	"strings"
	"sync"

	"github.com/dop251/goja"
)

type BuiltinFunction any

type Builtin struct {
	Name       string
	Function   any
	Definition string
}

var (
	builtinRegistry = make(map[string]Builtin)
	registryMutex   sync.RWMutex
)

func RegisterBuiltin[T any](name string, fn T) {
	builtinRegistry[name] = createBuiltin(name, fn)
}

func createBuiltin(name string, fn any) Builtin {
	fnValue := reflect.ValueOf(fn)
	fnType := fnValue.Type()

	tsDef := generateTypeScriptDefinition(name, fnType)

	return Builtin{
		Name:       name,
		Function:   fn,
		Definition: tsDef,
	}
}

func generateTypeScriptDefinition(name string, fnType reflect.Type) string {
	if fnType.Kind() != reflect.Func {
		return ""
	}

	var params []string
	for i := 0; i < fnType.NumIn(); i++ {
		params = append(params, fmt.Sprintf("arg%d: %s", i, goTypeToTSType(fnType.In(i))))
	}

	returnSignature := "void"
	if fnType.NumOut() > 0 {
		returnType := fnType.Out(0)
		returnSignature = goTypeToTSType(returnType)
	}

	return fmt.Sprintf("declare function %s(%s): %s;", name, strings.Join(params, ", "), returnSignature)
}

func goTypeToTSType(t reflect.Type) string {
	switch t.Kind() {
	case reflect.String:
		return "string"
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return "number"
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return "number"
	case reflect.Float32, reflect.Float64:
		return "number"
	case reflect.Bool:
		return "boolean"
	case reflect.Interface, reflect.Pointer:
		if t.String() == "goja.Value" {
			return "any"
		}
		return "any"
	case reflect.Slice:
		return fmt.Sprintf("%s[]", goTypeToTSType(t.Elem()))
	case reflect.Map:
		return "Record<string, any>"
	case reflect.Struct:
		return "any"
	default:
		return "any"
	}
}

func GetBuiltinsDeclarations() string {
	registryMutex.RLock()
	defer registryMutex.RUnlock()

	var decls []string
	for _, builtin := range builtinRegistry {
		decls = append(decls, builtin.Definition)
	}
	return strings.Join(decls, "\n")
}

func RegisterBuiltins(vm *goja.Runtime) {
	RegisterFetchBuiltin(vm)

	registryMutex.RLock()
	defer registryMutex.RUnlock()

	for name, builtin := range builtinRegistry {
		if builtin.Function != nil {
			_ = vm.Set(name, builtin.Function)
		}
	}
}

type FetchResult struct {
	OK      bool
	Status  int
	Body    string
	Headers map[string]string
}

func Fetch(url string, options map[string]any) (*FetchResult, error) {
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to fetch: %w", err)
	}
	defer func() {
		_ = resp.Body.Close()
	}()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read body: %w", err)
	}

	headers := make(map[string]string)
	for key, values := range resp.Header {
		if len(values) > 0 {
			headers[key] = values[0]
			headers[strings.ToLower(key)] = values[0]
		}
	}

	return &FetchResult{
		OK:      resp.StatusCode >= 200 && resp.StatusCode < 300,
		Status:  resp.StatusCode,
		Body:    string(body),
		Headers: headers,
	}, nil
}

func RegisterFetchBuiltin(vm *goja.Runtime) {
	_ = vm.Set("fetch", func(call goja.FunctionCall) goja.Value {
		if len(call.Arguments) < 1 {
			panic("fetch requires at least 1 argument")
		}

		url := call.Arguments[0].String()

		result, err := Fetch(url, nil)
		if err != nil {
			panic(err)
		}

		resultObj := vm.NewObject()
		_ = resultObj.Set("ok", result.OK)
		_ = resultObj.Set("status", result.Status)

		body := result.Body
		_ = resultObj.Set("text", func() string {
			return body
		})

		headersObj := vm.NewObject()
		headers := result.Headers
		_ = headersObj.Set("get", func(c goja.FunctionCall) goja.Value {
			if len(c.Arguments) < 1 {
				return goja.Undefined()
			}
			key := c.Arguments[0].String()
			return vm.ToValue(headers[key])
		})
		_ = resultObj.Set("headers", headersObj)

		return resultObj
	})

	builtinRegistry["fetch"] = Builtin{
		Name:       "fetch",
		Function:   nil,
		Definition: "declare function fetch(url: string, options?: any): PromiseLike<any>;",
	}
}

func init() {
}