package jellyfin

import (
	"context"
	"database/sql"
	"errors"
	"net/http"
	"strings"

	"github.com/mithral/vellum/internal/auth"
	"github.com/mithral/vellum/internal/catalog"
	"github.com/mithral/vellum/internal/httpx"
	"github.com/mithral/vellum/internal/jellyfin/dto"
	"github.com/mithral/vellum/internal/library"
	"github.com/mithral/vellum/internal/stream"
)

// handleItems is the browse workhorse for GET /Items. The /Users/{userId}/Items
// form delegates here; the token's user is authoritative for scoping.
func (h *Handlers) handleItems(w http.ResponseWriter, r *http.Request, u auth.User) {
	ctx := r.Context()
	q := r.URL.Query()

	libs, err := auth.VisibleLibraryIDs(ctx, h.db, u)
	if err != nil {
		h.fail(w, "visible libraries", err)
		return
	}
	if libs == nil {
		libs = []int64{}
	}

	startIndex := atoiDefault(q.Get("StartIndex"), 0)
	if startIndex < 0 {
		startIndex = 0
	}
	limit := atoiDefault(q.Get("Limit"), defaultLimit)
	if limit <= 0 || limit > maxLimit {
		limit = maxLimit
	}

	parentRaw := strings.TrimSpace(q.Get("ParentId"))
	recursive := parseBool(q.Get("Recursive"))
	search := strings.TrimSpace(q.Get("SearchTerm"))
	types := splitCSV(q.Get("IncludeItemTypes"))

	// Top level: no parent, not recursive, no search. Real clients expect the
	// user's views here, so the visible libraries are returned as
	// CollectionFolder items to drill into.
	if parentRaw == "" && !recursive && search == "" {
		h.writeViews(w, ctx, libs, startIndex, limit)
		return
	}

	// A user with no grants gets an empty page, never an error and never
	// content from another library.
	if len(libs) == 0 {
		writeItems(w, startIndex, 0, nil)
		return
	}

	query := listQuery{
		userID:         u.ID,
		libraryIDs:     libs,
		sortColumn:     sortColumn(q.Get("SortBy")),
		descending:     isDescending(q.Get("SortOrder")),
		limit:          limit,
		offset:         startIndex,
		searchTerm:     search,
		filters:        splitCSV(q.Get("Filters")),
		kinds:          dto.KindsForTypes(types),
		episodesOnly:   dto.EpisodesOnly(types),
		includeSources: containsFold(splitCSV(q.Get("Fields")), "MediaSources"),
	}

	if parentRaw != "" {
		pid, isLib, ok := dto.DecodeID(parentRaw)
		if !ok {
			// An unknown ParentId is an empty page, not an error: clients probe
			// ids and expect to be told there is nothing there.
			writeItems(w, startIndex, 0, nil)
			return
		}
		if isLib {
			if !containsInt64(libs, pid) {
				writeItems(w, startIndex, 0, nil)
				return
			}
			query.libraryIDs = []int64{pid}
		} else {
			// Children of an item, and only if that item is visible.
			visible, err := h.itemVisible(ctx, u, pid)
			if err != nil {
				h.fail(w, "check parent", err)
				return
			}
			if !visible {
				writeItems(w, startIndex, 0, nil)
				return
			}
			query.parentItemID = pid
		}
	}

	items, total, err := h.queryItems(ctx, query)
	if err != nil {
		h.fail(w, "list items", err)
		return
	}

	apiKey := tokenFromRequest(r)
	dtos := make([]dto.BaseItemDto, 0, len(items))
	for _, it := range items {
		dtos = append(dtos, dto.ToBaseItemDto(it, query.includeSources, apiKey))
	}
	writeItems(w, startIndex, total, dtos)
}

// handleUserItems serves GET /Users/{userId}/Items. The token's user is
// authoritative; a mismatched path id is a 404 (cross-user reads are not
// implemented — see the package notes).
func (h *Handlers) handleUserItems(w http.ResponseWriter, r *http.Request, u auth.User) {
	id, _, ok := dto.DecodeID(r.PathValue("userId"))
	if !ok || id != u.ID {
		httpx.WriteError(w, http.StatusNotFound, "user not found")
		return
	}
	h.handleItems(w, r, u)
}

// handleItem serves one BaseItemDto. A library id is answered as a folder so a
// client that treats views as items still works.
func (h *Handlers) handleItem(w http.ResponseWriter, r *http.Request, u auth.User) {
	id, isLib, ok := dto.DecodeID(r.PathValue("itemId"))
	if !ok {
		httpx.WriteError(w, http.StatusNotFound, "item not found")
		return
	}
	if isLib {
		lib, err := library.Get(r.Context(), h.db, id)
		if errors.Is(err, library.ErrNotFound) {
			httpx.WriteError(w, http.StatusNotFound, "item not found")
			return
		}
		if err != nil {
			h.fail(w, "load library", err)
			return
		}
		allowed, err := auth.CanAccessLibrary(r.Context(), h.db, u, id)
		if err != nil {
			h.fail(w, "check access", err)
			return
		}
		if !allowed {
			httpx.WriteError(w, http.StatusNotFound, "item not found")
			return
		}
		httpx.WriteJSON(w, http.StatusOK, dto.LibraryDto(lib))
		return
	}

	it, ok := h.authorizedItem(w, r, u, id)
	if !ok {
		return
	}
	v := dto.ItemView{Item: it}
	if err := h.attachFile(r.Context(), &v); err != nil {
		h.fail(w, "load file", err)
		return
	}
	if err := h.loadOverlay(r.Context(), u.ID, it.ID, &v); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			httpx.WriteError(w, http.StatusNotFound, "item not found")
			return
		}
		h.fail(w, "load item state", err)
		return
	}
	httpx.WriteJSON(w, http.StatusOK, dto.ToBaseItemDto(v, true, tokenFromRequest(r)))
}

// handleImagePrimary streams the cover bytes the scanner/web already extracted.
//
// It does not trigger extraction: NewHandlers has no cache directory, and the
// extraction path belongs to the web layer. An item whose cover has not been
// extracted yet simply 404s, which clients treat as "no artwork".
func (h *Handlers) handleImagePrimary(w http.ResponseWriter, r *http.Request, u auth.User) {
	id, isLib, ok := dto.DecodeID(r.PathValue("itemId"))
	if !ok || isLib {
		httpx.WriteError(w, http.StatusNotFound, "no cover available")
		return
	}
	if _, ok := h.authorizedItem(w, r, u, id); !ok {
		return
	}

	var path string
	err := h.db.QueryRowContext(r.Context(),
		`SELECT path FROM assets WHERE item_id = ? AND role = 'cover' LIMIT 1`, id).Scan(&path)
	if errors.Is(err, sql.ErrNoRows) {
		httpx.WriteError(w, http.StatusNotFound, "no cover available")
		return
	}
	if err != nil {
		h.fail(w, "load cover", err)
		return
	}

	w.Header().Set("Cache-Control", "public, max-age=86400")
	if err := stream.ServeFile(w, r, path); err != nil {
		httpx.WriteError(w, http.StatusNotFound, "no cover available")
		return
	}
}

// authorizedItem loads an item and confirms access, writing a 404 (never a 403,
// so existence is not disclosed) on failure. Both the load and the grant check
// live in catalog.LoadFor, which returns the same ErrNotFound for a missing
// item and an unreadable one.
func (h *Handlers) authorizedItem(w http.ResponseWriter, r *http.Request, u auth.User, id int64) (catalog.Item, bool) {
	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 catalog.Item{}, false
	}
	if err != nil {
		h.fail(w, "load item", err)
		return catalog.Item{}, false
	}
	return it, true
}

// writeViews returns the caller's visible libraries as CollectionFolder items,
// paginated like any other browse result.
func (h *Handlers) writeViews(w http.ResponseWriter, ctx context.Context, libs []int64, startIndex, limit int) {
	list, err := library.ListVisible(ctx, h.db, libs)
	if err != nil {
		h.fail(w, "list libraries", err)
		return
	}
	total := len(list)
	if startIndex > total {
		startIndex = total
	}
	end := startIndex + limit
	if end > total {
		end = total
	}
	items := make([]dto.BaseItemDto, 0, end-startIndex)
	for _, lib := range list[startIndex:end] {
		items = append(items, dto.LibraryDto(lib))
	}
	writeItems(w, startIndex, total, items)
}

func writeItems(w http.ResponseWriter, startIndex, total int, items []dto.BaseItemDto) {
	if items == nil {
		items = []dto.BaseItemDto{}
	}
	httpx.WriteJSON(w, http.StatusOK, dto.ItemQueryResult{
		Items:            items,
		TotalRecordCount: total,
		StartIndex:       startIndex,
	})
}