package ebooks

import (
	"database/sql"
	"errors"
	"log/slog"
	"net/http"
	"strconv"

	"github.com/mithral/vellum/internal/auth"
	"github.com/mithral/vellum/internal/catalog"
	"github.com/mithral/vellum/internal/httpx"
)

// Handlers serves ebook-specific endpoints.
type Handlers struct {
	db   *sql.DB
	log  *slog.Logger
	auth *auth.Authenticator
}

// NewHandlers builds the ebook HTTP layer.
func NewHandlers(db *sql.DB, log *slog.Logger, a *auth.Authenticator) *Handlers {
	return &Handlers{db: db, log: log, auth: a}
}

// Register mounts the routes.
func (h *Handlers) Register(mux *http.ServeMux) {
	mux.Handle("GET /api/v1/items/{id}/ebook", h.auth.Require(h.handleMetadata))
}

// handleMetadata parses the EPUB on demand and returns its metadata.
//
// Parsing on demand rather than at scan time keeps the scanner fast and means
// a fix to the parser applies immediately, without a rescan.
func (h *Handlers) handleMetadata(w http.ResponseWriter, r *http.Request, u auth.User) {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil || id <= 0 {
		httpx.WriteError(w, http.StatusBadRequest, "invalid item id")
		return
	}

	it, err := catalog.LoadFor(r.Context(), h.db, u, id)
	if errors.Is(err, catalog.ErrNotFound) {
		httpx.WriteError(w, http.StatusNotFound, "item not found")
		return
	}
	if err != nil {
		h.log.Error("load item", "err", err)
		httpx.WriteError(w, http.StatusInternalServerError, "internal server error")
		return
	}

	if it.Kind != Kind {
		httpx.WriteError(w, http.StatusBadRequest, "item is not an ebook")
		return
	}

	md, err := Parse(it.AbsPath())
	if err != nil {
		h.log.Warn("parse epub", "item", it.ID, "err", err)
		httpx.WriteError(w, http.StatusUnprocessableEntity, "could not parse epub")
		return
	}

	// Fall back to the scanner's title when the OPF has none.
	if md.Title == "" {
		md.Title = it.Title
	}
	httpx.WriteJSON(w, http.StatusOK, map[string]any{"metadata": md})
}