package metadata

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

	"github.com/mithral/vellum/internal/auth"
	"github.com/mithral/vellum/internal/httpx"
	"github.com/mithral/vellum/internal/jobs"
	"github.com/mithral/vellum/internal/media"
)

// Handlers serves metadata endpoints.
type Handlers struct {
	db    *sql.DB
	log   *slog.Logger
	auth  *auth.Authenticator
	queue *jobs.Queue
}

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

// Register mounts the routes.
func (h *Handlers) Register(mux *http.ServeMux) {
	mux.Handle("POST /api/v1/libraries/{id}/enrich", h.auth.RequireAdmin(http.HandlerFunc(h.handleEnrichLibrary)))
	mux.Handle("GET /api/v1/items/{id}/metadata", h.auth.Require(h.handleItemMetadata))
}

// handleEnrichLibrary queues enrichment for every unmatched item in a library.
func (h *Handlers) handleEnrichLibrary(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil || id <= 0 {
		httpx.WriteError(w, http.StatusBadRequest, "invalid library id")
		return
	}

	var exists int
	if err := h.db.QueryRowContext(r.Context(), `SELECT count(*) FROM libraries WHERE id = ?`, id).Scan(&exists); err != nil {
		h.fail(w, "check library", err)
		return
	}
	if exists == 0 {
		httpx.WriteError(w, http.StatusNotFound, "library not found")
		return
	}

	// Items that have no provider match yet. Already-matched items are skipped
	// so a second click is cheap rather than a re-query of every provider.
	rows, err := h.db.QueryContext(r.Context(), `
		SELECT i.id FROM media_items i
		WHERE i.library_id = ? AND i.missing = 0
		  AND NOT EXISTS (SELECT 1 FROM provider_ids p WHERE p.item_id = i.id)`, id)
	if err != nil {
		h.fail(w, "select items", err)
		return
	}
	defer rows.Close()

	var ids []int64
	for rows.Next() {
		var itemID int64
		if err := rows.Scan(&itemID); err != nil {
			h.fail(w, "scan item id", err)
			return
		}
		ids = append(ids, itemID)
	}
	if err := rows.Err(); err != nil {
		h.fail(w, "iterate items", err)
		return
	}

	queued := 0
	for _, itemID := range ids {
		if err := h.queue.Enqueue(r.Context(), JobKind, enrichPayload{ItemID: itemID}); err != nil {
			h.fail(w, "enqueue enrich", err)
			return
		}
		queued++
	}

	h.log.Info("enrichment queued", "library", id, "items", queued)
	httpx.WriteJSON(w, http.StatusAccepted, map[string]any{"queued": queued})
}

// handleItemMetadata reports what the catalogue knows about an item.
func (h *Handlers) handleItemMetadata(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 := media.LoadItem(r.Context(), h.db, id)
	if errors.Is(err, media.ErrItemNotFound) {
		httpx.WriteError(w, http.StatusNotFound, "item not found")
		return
	}
	if err != nil {
		h.fail(w, "load item", err)
		return
	}
	allowed, err := auth.CanAccessLibrary(r.Context(), h.db, u, it.LibraryID)
	if err != nil || !allowed {
		httpx.WriteError(w, http.StatusNotFound, "item not found")
		return
	}

	type providerID struct {
		Provider   string `json:"provider"`
		ExternalID string `json:"external_id"`
	}
	type fetch struct {
		Provider  string `json:"provider"`
		Status    string `json:"status"`
		Detail    string `json:"detail"`
		FetchedAt string `json:"fetched_at"`
	}

	ids := []providerID{}
	rows, err := h.db.QueryContext(r.Context(),
		`SELECT provider, external_id FROM provider_ids WHERE item_id = ? ORDER BY provider`, id)
	if err != nil {
		h.fail(w, "select provider ids", err)
		return
	}
	for rows.Next() {
		var p providerID
		if err := rows.Scan(&p.Provider, &p.ExternalID); err != nil {
			rows.Close()
			h.fail(w, "scan provider id", err)
			return
		}
		ids = append(ids, p)
	}
	rows.Close()

	fetches := []fetch{}
	frows, err := h.db.QueryContext(r.Context(),
		`SELECT provider, status, detail, fetched_at FROM metadata_fetch WHERE item_id = ? ORDER BY provider`, id)
	if err != nil {
		h.fail(w, "select fetches", err)
		return
	}
	defer frows.Close()
	for frows.Next() {
		var f fetch
		if err := frows.Scan(&f.Provider, &f.Status, &f.Detail, &f.FetchedAt); err != nil {
			h.fail(w, "scan fetch", err)
			return
		}
		fetches = append(fetches, f)
	}

	httpx.WriteJSON(w, http.StatusOK, map[string]any{
		"item_id":       id,
		"provider_ids":  ids,
		"fetch_history": fetches,
	})
}

func (h *Handlers) fail(w http.ResponseWriter, what string, err error) {
	h.log.Error(what, "err", err)
	httpx.WriteError(w, http.StatusInternalServerError, "internal server error")
}