package handlers

import (
	"errors"
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/jackc/pgx/v5"

	"booklib/internal/bookfile"
	"booklib/internal/store"
)

func (h *H) getBookRow(c *gin.Context, id int64) (store.Book, bool) {
	b, e := h.st.GetBook(c, id)
	if e != nil {
		if errors.Is(e, pgx.ErrNoRows) {
			err(c, http.StatusNotFound, "not_found", "no such book")
			return store.Book{}, false
		}
		dbErr(c, e)
		return store.Book{}, false
	}
	return b, true
}

func (h *H) bookFromParam(c *gin.Context) (store.Book, bool) {
	id, e := strconv.ParseInt(c.Param("id"), 10, 64)
	if e != nil {
		err(c, http.StatusBadRequest, "bad_request", "bad id")
		return store.Book{}, false
	}
	return h.getBookRow(c, id)
}

func (h *H) getLibRow(c *gin.Context, id int64) (store.Library, bool) {
	l, e := h.st.GetLibrary(c, id)
	if e != nil {
		if errors.Is(e, pgx.ErrNoRows) {
			err(c, http.StatusNotFound, "not_found", "no such library")
			return store.Library{}, false
		}
		dbErr(c, e)
		return store.Library{}, false
	}
	return l, true
}

// absBookPath: books.path 永远相对且不含 ..;拼接后二次前缀校验(纵深防御)
func absBookPath(root string, b store.Book) (string, error) {
	abs := filepath.Join(root, filepath.FromSlash(b.Path))
	if filepath.Clean(abs) != abs || !hasPrefixDir(abs, root) {
		return "", os.ErrPermission
	}
	return abs, nil
}

func hasPrefixDir(p, dir string) bool {
	rel, err := filepath.Rel(filepath.Clean(dir), filepath.Clean(p))
	return err == nil && rel != ".." && !strings.HasPrefix(rel, ".."+string(os.PathSeparator))
}

func bookJSON(b store.Book, percent float64, libraryName string) gin.H {
	h := bookfile.Hash(b.FileSize, b.ModTS)
	j := gin.H{
		"id": b.ID, "library_id": b.LibraryID, "path": b.Path, "title": b.Title,
		"format": b.Format, "size": b.FileSize, "mtime": b.ModTS, "pages": b.PageCount,
		"state": b.State, "error": b.ErrMsg, "added_at": b.AddedAt.Format(time.RFC3339),
		"percent":   percent,
		"cover_url": fmt.Sprintf("/api/books/%d/cover?v=%s", b.ID, h),
	}
	if b.Format == "cbz" {
		j["pages_url"] = fmt.Sprintf("/api/books/%d/pages", b.ID)
		j["page_url_fmt"] = fmt.Sprintf("/api/books/%d/pages/%%d?v=%s", b.ID, h)
	} else {
		j["file_url"] = fmt.Sprintf("/api/books/%d/file?v=%s", b.ID, h)
	}
	if libraryName != "" {
		j["library"] = libraryName
	}
	return j
}

func (h *H) ListBooks(c *gin.Context) {
	libID, _ := strconv.ParseInt(c.Query("library"), 10, 64)
	views, e := h.st.ListBooks(c, libID, c.Query("q"), c.Query("prefix"), uid(c))
	if e != nil {
		dbErr(c, e)
		return
	}
	out := make([]gin.H, 0, len(views))
	for _, v := range views {
		out = append(out, bookJSON(v.Book, v.Percent, v.LibraryName))
	}
	c.JSON(http.StatusOK, out)
}

func (h *H) GetBook(c *gin.Context) {
	b, ok := h.bookFromParam(c)
	if !ok {
		return
	}
	p, e := h.st.GetProgress(c, uid(c), b.LibraryID, b.Path) // ErrNoRows → 零值 percent
	if e != nil && !errors.Is(e, pgx.ErrNoRows) {
		dbErr(c, e)
		return
	}
	lib, e := h.st.GetLibrary(c, b.LibraryID)
	if e != nil && !errors.Is(e, pgx.ErrNoRows) { // 库被并发删则留空 library 名,书仍可见
		dbErr(c, e)
		return
	}
	c.JSON(http.StatusOK, bookJSON(b, p.Percent, lib.Name))
}

func (h *H) DeleteBook(c *gin.Context) {
	b, ok := h.bookFromParam(c)
	if !ok {
		return
	}
	lib, ok := h.getLibRow(c, b.LibraryID)
	if !ok {
		return
	}
	root, ok := h.libRoot(c, lib)
	if !ok {
		return
	}
	abs, e := absBookPath(root, b)
	if e != nil {
		err(c, http.StatusForbidden, "forbidden", "unsafe path")
		return
	}
	if e := os.Remove(abs); e != nil && !os.IsNotExist(e) {
		err(c, http.StatusInternalServerError, "internal", "remove file")
		return
	}
	key := bookfile.DirKey(b.ID, bookfile.Hash(b.FileSize, b.ModTS))
	os.RemoveAll(bookfile.CoverDir(h.cfg.CacheDir, key))
	os.RemoveAll(bookfile.PagesDir(h.cfg.CacheDir, key))
	if e := h.st.DeleteBook(c, b.ID); e != nil {
		dbErr(c, e)
		return
	}
	c.Status(http.StatusNoContent)
}