package faultRecordFile

import (
	"archive/tar"
	"bytes"
	"compress/bzip2"
	"compress/gzip"
	"errors"
	"fmt"
	"io"
	"path"
	"sort"
	"strconv"
	"strings"
)

const (
	maxEntrySize   = 16 << 20 // 单个文件上限
	maxArchiveRead = 64 << 20 // 解压总量上限
	fileFailure    = "failuredata"
	fileWaveform   = "waveformdata"
	indexDirPrefix = "index_"
)

// RecordFiles 压缩包中一条记录的两个文件（十六进制文本原文）
type RecordFiles struct {
	Batch        string `json:"batch"`
	Sn           string `json:"sn"`
	Index        int    `json:"index"`
	FailureData  []byte `json:"-"`
	WaveformData []byte `json:"-"`
}

// openArchive 按文件头判断压缩格式；扩展名为 .tar.bz2 的文件实际可能是 gzip
func openArchive(data []byte) (io.Reader, error) {
	switch {
	case len(data) >= 2 && data[0] == 0x1f && data[1] == 0x8b:
		return gzip.NewReader(bytes.NewReader(data))
	case len(data) >= 3 && string(data[:3]) == "BZh":
		return bzip2.NewReader(bytes.NewReader(data)), nil
	default:
		return bytes.NewReader(data), nil // 未压缩的 tar
	}
}

// ExtractArchive 解出 <batch>/<sn>/index_<n>/{failuredata,waveformdata}，其他文件忽略
func ExtractArchive(data []byte) ([]RecordFiles, error) {
	zr, err := openArchive(data)
	if err != nil {
		return nil, fmt.Errorf("open archive: %w", err)
	}
	tr := tar.NewReader(io.LimitReader(zr, maxArchiveRead))

	records := map[string]*RecordFiles{}
	for {
		h, err := tr.Next()
		if errors.Is(err, io.EOF) {
			break
		}
		if err != nil {
			return nil, fmt.Errorf("read archive: %w", err)
		}
		if h.Typeflag != tar.TypeReg {
			continue
		}
		parts := strings.Split(strings.Trim(path.Clean(h.Name), "/"), "/")
		if len(parts) < 4 {
			continue
		}
		name := parts[len(parts)-1]
		if name != fileFailure && name != fileWaveform {
			continue
		}
		idxStr, ok := strings.CutPrefix(parts[len(parts)-2], indexDirPrefix)
		if !ok {
			continue
		}
		idx, err := strconv.Atoi(idxStr)
		if err != nil {
			continue
		}
		if h.Size > maxEntrySize {
			return nil, fmt.Errorf("%s too large: %d bytes", h.Name, h.Size)
		}
		content, err := io.ReadAll(io.LimitReader(tr, maxEntrySize))
		if err != nil {
			return nil, fmt.Errorf("read %s: %w", h.Name, err)
		}

		batch, sn := parts[len(parts)-4], parts[len(parts)-3]
		key := batch + "/" + sn + "/" + idxStr
		rf, ok := records[key]
		if !ok {
			rf = &RecordFiles{Batch: batch, Sn: sn, Index: idx}
			records[key] = rf
		}
		if name == fileFailure {
			rf.FailureData = bytes.TrimSpace(content)
		} else {
			rf.WaveformData = bytes.TrimSpace(content)
		}
	}

	list := make([]RecordFiles, 0, len(records))
	for _, rf := range records {
		list = append(list, *rf)
	}
	sort.Slice(list, func(i, j int) bool {
		if list[i].Sn != list[j].Sn {
			return list[i].Sn < list[j].Sn
		}
		return list[i].Index < list[j].Index
	})
	return list, nil
}

// ParseArchive 解压并解析全部记录；缺少任一文件的记录返回错误
func ParseArchive(data []byte, deviceType string) ([]Record, error) {
	files, err := ExtractArchive(data)
	if err != nil {
		return nil, err
	}
	if len(files) == 0 {
		return nil, fmt.Errorf("no record found in archive")
	}
	records := make([]Record, 0, len(files))
	for _, f := range files {
		if len(f.FailureData) == 0 || len(f.WaveformData) == 0 {
			return nil, fmt.Errorf("record %s/%s/index_%d is incomplete", f.Batch, f.Sn, f.Index)
		}
		rec, err := ParseRecordFiles(f, deviceType)
		if err != nil {
			return nil, fmt.Errorf("record %s/%s/index_%d: %w", f.Batch, f.Sn, f.Index, err)
		}
		records = append(records, rec)
	}
	return records, nil
}