package handlers

import (
	"errors"
	"net/http"
	"os"
	"strconv"

	"github.com/gin-gonic/gin"

	"booklib/internal/ports"
	"booklib/internal/upload"
)

// 分片上传:HTTP 层只做参数绑定与错误映射,域逻辑(指纹续传/分片落盘/拼接/清扫)
// 全部在 internal/upload;会话清扫由 scanner ticker 接管(B16),不在请求路径。

// maxChunkBytes 与 upload 包内常量同值,作为 PutPart 的防御性读取上限。
const maxChunkBytes = 32 << 20

func (h *H) UploadInit(c *gin.Context) {
	id, ok := idParam(c)
	if !ok {
		return
	}
	lib, ok := h.getLib(c, id)
	if !ok {
		return
	}
	if _, ok := h.libRoot(c, lib); !ok {
		return
	}
	var req struct {
		Name      string `json:"name"`
		Size      int64  `json:"size"`
		ChunkSize int64  `json:"chunkSize"`
	}
	if c.ShouldBindJSON(&req) != nil {
		err(c, http.StatusBadRequest, "bad_request", "name, size required")
		return
	}
	uid, e := h.up.Init(c, lib.ID, req.Name, req.Size, req.ChunkSize)
	if e != nil {
		h.mapUploadErr(c, e)
		return
	}
	c.JSON(http.StatusOK, gin.H{"uploadId": uid})
}

func (h *H) UploadStatus(c *gin.Context) {
	recv, e := h.up.Status(c, c.Param("uid"))
	if e != nil {
		h.mapUploadErr(c, e)
		return
	}
	c.JSON(http.StatusOK, gin.H{"received": recv})
}

func (h *H) UploadPart(c *gin.Context) {
	uid := c.Param("uid")
	idx, e := strconv.ParseInt(c.Param("index"), 10, 64)
	if e != nil {
		err(c, http.StatusBadRequest, "bad_request", "bad part index")
		return
	}
	// maxSize 防御性上限:分片声明大小由会话 meta 决定,这里再垫一层 32MB 全局上限
	e = h.up.PutPart(c, uid, idx, c.Request.Body, maxChunkBytes)
	if e != nil {
		h.mapUploadErr(c, e)
		return
	}
	c.JSON(http.StatusAccepted, gin.H{"accepted": true})
}

func (h *H) UploadComplete(c *gin.Context) {
	uid := c.Param("uid")
	libID, e := h.up.LibraryID(c, uid)
	if e != nil {
		h.mapUploadErr(c, e)
		return
	}
	lib, e := h.libs.GetLibrary(c, libID)
	if e != nil {
		dbErr(c, e)
		return
	}
	root, ok := h.libRoot(c, lib)
	if !ok {
		return
	}
	rel, e := h.up.Complete(c, uid, root)
	if e != nil {
		h.mapUploadErr(c, e)
		return
	}
	c.JSON(http.StatusAccepted, gin.H{"accepted": true, "path": rel})
}

// mapUploadErr 把 upload 包的 sentinel 错误映射为原契约的 status/code/message。
func (h *H) mapUploadErr(c *gin.Context, e error) {
	switch {
	case errors.Is(e, ports.ErrTooLarge):
		err(c, http.StatusRequestEntityTooLarge, "too_large", "file exceeds upload limit of "+strconv.FormatInt(h.cfg.UploadMaxMB, 10)+"MB")
	case errors.Is(e, upload.ErrBadName):
		err(c, http.StatusBadRequest, "bad_request", "bad name")
	case errors.Is(e, upload.ErrBadFormat):
		err(c, http.StatusBadRequest, "bad_format", "extension must be cbz/pdf/epub/txt/md")
	case errors.Is(e, upload.ErrBadSize):
		err(c, http.StatusBadRequest, "bad_request", "bad size")
	case errors.Is(e, upload.ErrBadChunk):
		err(c, http.StatusBadRequest, "bad_request", "chunkSize must be <= 33554432")
	case errors.Is(e, upload.ErrBadUploadID):
		err(c, http.StatusBadRequest, "bad_request", "bad upload id")
	case errors.Is(e, upload.ErrBadIndex):
		err(c, http.StatusBadRequest, "bad_request", "bad part index")
	case errors.Is(e, upload.ErrPartTooBig):
		err(c, http.StatusRequestEntityTooLarge, "too_large", "part exceeds declared size")
	case errors.Is(e, upload.ErrPartSizeMismatch):
		err(c, http.StatusRequestEntityTooLarge, "too_large", "part size mismatch")
	case errors.Is(e, ports.ErrNotFound):
		err(c, http.StatusNotFound, "not_found", "no such upload")
	case errors.Is(e, upload.ErrCorrupt):
		err(c, http.StatusInternalServerError, "internal", "corrupt session")
	case errors.Is(e, ports.ErrIncomplete):
		err(c, http.StatusBadRequest, "bad_request", "upload incomplete; missing or corrupt parts, re-upload them")
	case errors.Is(e, ports.ErrSizeMismatch):
		err(c, http.StatusBadRequest, "bad_request", "total size mismatch")
	case errors.Is(e, os.ErrInvalid), errors.Is(e, os.ErrExist):
		err(c, http.StatusForbidden, "forbidden", e.Error())
	case errors.Is(e, os.ErrPermission), errors.Is(e, os.ErrClosed):
		err(c, http.StatusInternalServerError, "internal", "io error")
	default:
		var oe *upload.OpError
		if errors.As(e, &oe) {
			err(c, http.StatusInternalServerError, "internal", oe.Op)
			return
		}
		err(c, http.StatusInternalServerError, "internal", "upload failed")
	}
}