package utils

import (
	"context"
	"errors"
	"image"
	_ "image/jpeg"
	_ "image/png"
	"os"
	"time"

	"github.com/makiuchi-d/gozxing"
	multiqrcode "github.com/makiuchi-d/gozxing/multi/qrcode"
	"github.com/makiuchi-d/gozxing/qrcode"
	_ "golang.org/x/image/bmp"
)

var (
	ErrQRCodeNotFound  = errors.New("未检测到二维码")
	ErrQRCodeDecodeFail = errors.New("二维码解码失败")
	ErrImageDecode     = errors.New("图片无法解析")
)

func DecodeFile(ctx context.Context, filePath string, timeout time.Duration) ([]string, error) {
	/*
		解码封装：
		- 统一在此处施加“单张超时”，避免上层 caller 需要重复处理
		- 使用 goroutine 执行实际解码，让 ctx 超时/取消可以及时返回
		- 返回值为 []string：支持“单图多码”
	*/
	if timeout > 0 {
		var cancel context.CancelFunc
		ctx, cancel = context.WithTimeout(ctx, timeout)
		defer cancel()
	}

	type result struct {
		contents []string
		err      error
	}

	ch := make(chan result, 1)
	go func() {
		contents, err := decodeFile(filePath)
		ch <- result{contents: contents, err: err}
	}()

	select {
	case <-ctx.Done():
		return nil, ctx.Err()
	case r := <-ch:
		return r.contents, r.err
	}
}

func decodeFile(filePath string) ([]string, error) {
	/*
		识别策略：
		1) 先尝试多码识别（QRCodeMultiReader）
		2) 如果多码失败，再回退到单码识别（QRCodeReader）
		失败时返回稳定的业务错误（ErrImageDecode/ErrQRCodeNotFound/ErrQRCodeDecodeFail）
	*/
	f, err := os.Open(filePath)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	img, _, err := image.Decode(f)
	if err != nil {
		return nil, ErrImageDecode
	}

	bmp, err := gozxing.NewBinaryBitmapFromImage(img)
	if err != nil {
		return nil, ErrImageDecode
	}

	mr := multiqrcode.NewQRCodeMultiReader()
	rs, err := mr.DecodeMultiple(bmp, nil)
	if err == nil && len(rs) > 0 {
		return uniqueTexts(rs), nil
	}

	r := qrcode.NewQRCodeReader()
	single, err2 := r.Decode(bmp, nil)
	if err2 == nil && single != nil {
		return []string{single.GetText()}, nil
	}

	if err2 != nil {
		return nil, ErrQRCodeDecodeFail
	}
	return nil, ErrQRCodeNotFound
}

func uniqueTexts(rs []*gozxing.Result) []string {
	seen := map[string]struct{}{}
	out := make([]string, 0, len(rs))
	for _, r := range rs {
		if r == nil {
			continue
		}
		t := r.GetText()
		if t == "" {
			continue
		}
		if _, ok := seen[t]; ok {
			continue
		}
		seen[t] = struct{}{}
		out = append(out, t)
	}
	return out
}