package main

import (
	"archive/tar"
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"hash/crc64"
	"io"
	"net/http"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/go-redis/redis/v8"
	"github.com/gorilla/mux"
)

type DumpChunkName struct {
	Key      string `json:"key"`
	Distance int    `json:"distance"`
	Cursor   int64  `json:"cursor"`
	Checksum uint64 `json:"checksum"`
}

func (that *GlobalBackfeedManager) HandleLoad(res http.ResponseWriter, req *http.Request) {
	defer req.Body.Close()
	reqBuffer := bufio.NewReader(req.Body)
	tarReader := tar.NewReader(reqBuffer)
	existed := []string{}
	imported := []string{}
	recreate := req.URL.Query().Get("recreate") != ""
	skipKeys := map[string]struct{}{}
	for {
		header, err := tarReader.Next()
		if err != nil {
			if err == io.EOF {
				break
			}
			WriteResponse(res, http.StatusInternalServerError, err)
			return
		}
		if header.Typeflag != tar.TypeReg {
			WriteResponse(res, http.StatusBadRequest, fmt.Errorf("[chunk %s] unexpected tar entry type: %d", header.Name, header.Typeflag))
			return
		}
		var name DumpChunkName
		if err := json.Unmarshal([]byte(header.Name), &name); err != nil {
			WriteResponse(res, http.StatusBadRequest, fmt.Errorf("[chunk %s] invalid chunk name: %s", header.Name, err))
			return
		}
		if strings.Count(name.Key, ":") < 2 {
			WriteResponse(res, http.StatusBadRequest, fmt.Errorf("[chunk %s] invalid chunk key: %s", header.Name, name.Key))
			return
		}
		chunk := make([]byte, header.Size)
		if _, err := io.ReadFull(tarReader, chunk); err != nil {
			WriteResponse(res, http.StatusBadRequest, fmt.Errorf("[chunk %s] failed to read chunk: %s", header.Name, err))
			return
		}
		checksum := crc64.Checksum(chunk, crc64.MakeTable(crc64.ECMA))
		if name.Checksum != checksum {
			WriteResponse(res, http.StatusBadRequest, fmt.Errorf("[chunk %s] invalid chunk checksum: %d (expected) != %d (actual)", header.Name, name.Checksum, checksum))
			return
		}
		if len(chunk) == 0 && name.Cursor == 0 {
			continue
		}
		if name.Distance == 0 {
			if exists, err := that.BackfeedRedis.Exists(req.Context(), name.Key).Result(); err != nil && err != redis.Nil {
				WriteResponse(res, http.StatusInternalServerError, fmt.Errorf("[chunk %s] failed to check key existence: %s", header.Name, err))
				return
			} else if exists == 1 {
				existed = append(existed, name.Key)
				if recreate {
					if _, err := that.BackfeedRedis.Unlink(req.Context(), name.Key).Result(); err != nil {
						WriteResponse(res, http.StatusInternalServerError, fmt.Errorf("[chunk %s] failed to unlink key: %s", header.Name, err))
						return
					}
				} else {
					skipKeys[name.Key] = struct{}{}
					continue
				}
			}
		}
		if _, has := skipKeys[name.Key]; has {
			continue
		}
		if _, err := that.BackfeedRedis.Do(req.Context(), "bf.loadchunk", name.Key, name.Cursor, chunk).Result(); err != nil {
			WriteResponse(res, http.StatusInternalServerError, fmt.Errorf("[chunk %s] failed to import chunk: %s", header.Name, err))
			return
		}
		if name.Distance == 0 {
			imported = append(imported, name.Key)
		}
	}
	WriteResponse(res, http.StatusOK, map[string]any{
		"existed":  existed,
		"imported": imported,
	})
}

func (that *GlobalBackfeedManager) HandleDump(res http.ResponseWriter, req *http.Request) {
	vars := mux.Vars(req)
	key := vars["key"]
	if key == "" {
		key = "*:*:*"
	}
	if strings.Count(key, ":") < 2 {
		WriteResponse(res, http.StatusBadRequest, fmt.Errorf("invalid key format"))
		return
	}
	lock := sync.Mutex{}
	keys := []string{}
	if err := that.BackfeedRedis.ForEachShard(req.Context(), func(ctx context.Context, client *redis.Client) error {
		cursor := uint64(0)
		var shardKeys []string
		for {
			var err error
			var keysBatch []string
			keysBatch, cursor, err = client.Scan(ctx, cursor, key, 1000).Result()
			if err != nil && err != redis.Nil {
				return err
			}
			shardKeys = append(shardKeys, keysBatch...)
			if cursor == 0 {
				break
			}
		}
		lock.Lock()
		defer lock.Unlock()
		keys = append(keys, shardKeys...)
		return nil
	}); err != nil && err != redis.Nil {
		WriteResponse(res, http.StatusInternalServerError, err)
		return
	}
	sort.Strings(keys)
	hasJsonAcceptHeader := false
	for _, accept := range strings.Split(req.Header.Get("Accept"), ",") {
		accept = strings.TrimSpace(accept)
		if accept == "application/json" || strings.HasPrefix(accept, "application/json;") {
			hasJsonAcceptHeader = true
			break
		}
	}
	if hasJsonAcceptHeader {
		WriteResponse(res, http.StatusOK, keys)
		return
	}
	if len(keys) == 0 {
		WriteResponse(res, http.StatusNoContent, nil)
		return
	}
	resBuf := bufio.NewWriterSize(res, 16*1024*1024)
	defer resBuf.Flush()
	tarWriter := tar.NewWriter(resBuf)
	defer tarWriter.Close()
	pipe := that.BackfeedRedis.Pipeline()
	writeError := func(err error) {
		errChunk := []byte(err.Error())
		if err := tarWriter.WriteHeader(&tar.Header{
			Typeflag: tar.TypeReg,
			Name:     "error",
			Size:     int64(len(errChunk)),
			Mode:     0600,
			PAXRecords: map[string]string{
				"ARCHIVETEAM.bffchunk.error": fmt.Sprintf("%s", err),
			},
			Format: tar.FormatPAX,
		}); err != nil {
			return
		}
		if _, err := tarWriter.Write(errChunk); err != nil {
			return
		}
	}
	for _, key := range keys {
		cursor := int64(0)
		for i := 0; ; i++ {
			rawResResult := pipe.Do(req.Context(), "bf.scandump", key, cursor)
			tsStringResult := that.BackfeedRedis.HGet(req.Context(), ":last_ts", key)
			_, err := pipe.Exec(req.Context())
			if err != nil && err != redis.Nil {
				writeError(err)
				return
			}
			rawRes, err := rawResResult.Result()
			if err != nil && err != redis.Nil {
				writeError(err)
				return
			}
			if rawRes == nil {
				break
			}
			resSlice, ok := rawRes.([]any)
			if !ok {
				writeError(fmt.Errorf("unexpected response type: %T", rawRes))
				return
			}
			if len(resSlice) != 2 {
				writeError(fmt.Errorf("unexpected response length: %d", len(resSlice)))
				return
			}
			cursor, ok = resSlice[0].(int64)
			if !ok {
				writeError(fmt.Errorf("unexpected response first element type: %T", resSlice[0]))
				return
			}
			chunkString, ok := resSlice[1].(string)
			if !ok {
				writeError(fmt.Errorf("unexpected response second element type: %T", resSlice[1]))
				return
			}
			chunk := []byte(chunkString)

			lastAccess := time.Time{}
			tsString, err := tsStringResult.Result()
			if err == nil && tsString != "" {
				ts, err := strconv.ParseInt(tsString, 10, 64)
				if err == nil {
					lastAccess = time.Unix(ts, 0)
				}
			}

			nameStruct := DumpChunkName{
				Key:      key,
				Cursor:   cursor,
				Distance: i,
				Checksum: crc64.Checksum(chunk, crc64.MakeTable(crc64.ECMA)),
			}
			name, err := json.Marshal(nameStruct)
			if err != nil {
				writeError(err)
				return
			}
			if err := tarWriter.WriteHeader(&tar.Header{
				Typeflag:   tar.TypeReg,
				Name:       string(name),
				Size:       int64(len(chunk)),
				Mode:       0600,
				ModTime:    lastAccess,
				AccessTime: lastAccess,
				ChangeTime: lastAccess,
				PAXRecords: map[string]string{
					"ARCHIVETEAM.bffchunk.key":      key,
					"ARCHIVETEAM.bffchunk.cursor":   fmt.Sprintf("%d", cursor),
					"ARCHIVETEAM.bffchunk.distance": fmt.Sprintf("%d", i),
					"ARCHIVETEAM.bffchunk.checksum": fmt.Sprintf("%d", nameStruct.Checksum),
				},
				Format: tar.FormatPAX,
			}); err != nil {
				writeError(err)
				return
			}
			if _, err := tarWriter.Write(chunk); err != nil {
				writeError(err)
				return
			}
			if cursor == 0 && len(chunk) == 0 {
				break
			}
		}
	}
}