// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//go:build js && wasm

package webui

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"syscall/js"

	"github.com/xiaoqidun/ofdgo"
)

const (
	platformTypeNumber   = js.TypeNumber
	platformTypeString   = js.TypeString
	platformTypeBoolean  = js.TypeBoolean
	platformTypeObject   = js.TypeObject
	platformTypeFunction = js.TypeFunction
)

// platformValue 浏览器参数值
type platformValue = js.Value

// RunWASM 注册浏览器WASM接口并阻塞运行
func RunWASM() {
	e := &businessEngine{}
	asynchronous := map[string]bool{
		"ofdgoDetectFormat":     true,
		"ofdgoExportVersion":    true,
		"ofdgoConvertPDF":       true,
		"ofdgoConvertFile":      true,
		"ofdgoPackFiles":        true,
		"ofdgoExportPage":       true,
		"ofdgoExportDocument":   true,
		"ofdgoExportAttachment": true,
		"ofdgoExportMedia":      true,
		"ofdgoResources":        true,
		"ofdgoExportResource":   true,
		"ofdgoExportImages":     true,
		"ofdgoImportImages":     true,
		"ofdgoImportPages":      true,
		"ofdgoImportDocuments":  true,
		"ofdgoSaveDocument":     true,
		"ofdgoPrepareSave":      true,
		"ofdgoSaveSnapshot":     true,
		"ofdgoSetEncryption":    true,
		"ofdgoSaveSigned":       true,
	}
	for name, callback := range e.businessCommands() {
		if asynchronous[name] {
			registerAsyncCallback(name, callback)
		} else {
			registerCallback(name, callback)
		}
	}
	select {}
}

// awaitExport 等待浏览器处理导出检查点
// 入参: fn 浏览器回调, args 回调参数
// 返回: error 写入错误或取消原因
func awaitExport(fn js.Value, args ...any) error {
	done := make(chan error)
	callback := js.FuncOf(func(this js.Value, args []js.Value) any {
		var err error
		if args[1].Bool() {
			err = context.Canceled
		} else if message := args[0].String(); message != "" {
			err = fmt.Errorf("%s", message)
		}
		done <- err
		return nil
	})
	defer callback.Release()
	fn.Invoke(append(args, callback)...)
	return <-done
}

// registerCallback 注册浏览器回调函数
// 入参: name 回调名称, fn 回调函数
func registerCallback(name string, fn func([]js.Value) (any, error)) {
	cb := js.FuncOf(func(this js.Value, args []js.Value) any {
		return callbackResult(fn, args)
	})
	js.Global().Set(name, cb)
}

// registerAsyncCallback 注册异步回调，为浏览器处理数据和取消请求让出事件循环
// 入参: name 回调名称, fn 回调函数
func registerAsyncCallback(name string, fn func([]js.Value) (any, error)) {
	cb := js.FuncOf(func(this js.Value, args []js.Value) any {
		executor := js.FuncOf(func(this js.Value, callbacks []js.Value) any {
			resolve := callbacks[0]
			go func() {
				resolve.Invoke(callbackResult(fn, args))
			}()
			return nil
		})
		defer executor.Release()
		return js.Global().Get("Promise").New(executor)
	})
	js.Global().Set(name, cb)
}

// callbackResult 转换浏览器接口结果
// 入参: fn 回调函数, args 回调参数
// 返回: any 浏览器结果
func callbackResult(fn func([]js.Value) (any, error), args []js.Value) any {
	data, err := (&businessEngine{}).safeCall(fn, args)
	if err != nil {
		result := failureResult(err)
		return (&businessEngine{}).encodeResult(result)
	}
	if result, ok := data.(js.Value); ok {
		return result
	}
	return (&businessEngine{}).encodeResult(apiResult{OK: true, Data: data})
}

// loadConversionFont 按需读取浏览器已授权字体，不预读系统字体目录
// 入参: load 浏览器读取函数, name 字体文件名
// 返回: []byte 字体内容, error 读取错误或取消原因
func (e *businessEngine) loadConversionFont(load js.Value, name string) ([]byte, error) {
	done := make(chan error, 1)
	var data []byte
	callback := js.FuncOf(func(this js.Value, args []js.Value) any {
		var err error
		if args[2].Bool() {
			err = context.Canceled
		} else if message := args[1].String(); message != "" {
			err = fmt.Errorf("%s", message)
		} else {
			data, err = e.bytesFromJS(args[0])
		}
		done <- err
		return nil
	})
	defer callback.Release()
	load.Invoke(name, callback)
	err := <-done
	return data, err
}

// successResult 创建成功接口结果
// 入参: data 返回数据
// 返回: js.Value 接口结果
func successResult(data any) js.Value {
	result := js.Global().Get("Object").New()
	result.Set("ok", true)
	result.Set("data", data)
	return result
}

// bytesToJS 将字节数据转换为Uint8Array
// 入参: data 字节数据
// 返回: js.Value Uint8Array对象
func bytesToJS(data []byte) js.Value {
	value := js.Global().Get("Uint8Array").New(len(data))
	js.CopyBytesToJS(value, data)
	return value
}

// bytesFromJS 从浏览器值读取二进制数据
// 入参: value 浏览器值
// 返回: []byte 二进制数据, error 错误信息
func (e *businessEngine) bytesFromJS(value js.Value) ([]byte, error) {
	if value.IsUndefined() || value.IsNull() {
		return nil, fmt.Errorf("missing binary data")
	}
	uint8Array := js.Global().Get("Uint8Array")
	arrayBuffer := js.Global().Get("ArrayBuffer")
	if value.InstanceOf(arrayBuffer) {
		value = uint8Array.New(value)
	}
	if !value.InstanceOf(uint8Array) {
		return nil, fmt.Errorf("binary data must be Uint8Array or ArrayBuffer")
	}
	data := make([]byte, value.Get("byteLength").Int())
	if n := js.CopyBytesToGo(data, value); n != len(data) {
		return nil, fmt.Errorf("copied %d of %d bytes", n, len(data))
	}
	return data, nil
}

// platformValueOf 转换浏览器参数
func platformValueOf(v any) platformValue { return js.ValueOf(v) }

// platformNull 返回空参数
func platformNull() platformValue { return js.Null() }

// platformCopyBytes 复制浏览器字节
func platformCopyBytes(dst []byte, src platformValue) int { return js.CopyBytesToGo(dst, src) }

// platformJSON 编码小参数
func platformJSON(v platformValue) string {
	return js.Global().Get("JSON").Call("stringify", v).String()
}

// platformParseJSON 解析结构参数
func platformParseJSON(data []byte) map[string]any {
	var result map[string]any
	if err := json.Unmarshal(data, &result); err != nil {
		panic(err)
	}
	return result
}

// inputFromValue 读取浏览器随机输入或二进制数据
func (e *businessEngine) inputFromValue(value platformValue) (*ofdgo.Input, error) {
	if value.Type() == platformTypeObject && !value.IsNull() && value.Get("read").Type() == platformTypeFunction {
		return ofdgo.NewInput(&browserReaderAt{read: value.Get("read"), size: int64(value.Get("size").Float())}, int64(value.Get("size").Float()))
	}
	data, err := e.bytesFromJS(value)
	if err != nil {
		return nil, err
	}
	return ofdgo.NewInput(bytes.NewReader(data), int64(len(data)))
}