package media

import (
	"database/sql"
	"errors"
	"log/slog"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"

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

// Handlers serves the generic per-item endpoints.
type Handlers struct {
	db       *sql.DB
	log      *slog.Logger
	auth     *auth.Authenticator
	cacheDir string
}

// NewHandlers builds the media HTTP layer. cacheDir is where covers and
// extracted pages are written.
func NewHandlers(db *sql.DB, log *slog.Logger, a *auth.Authenticator, cacheDir string) *Handlers {
	return &Handlers{db: db, log: log, auth: a, cacheDir: cacheDir}
}

// Register mounts the routes.
//
// The home screen is not registered here: it is an aggregate over items, not an
// item resource, and it lives in internal/home.
func (h *Handlers) Register(mux *http.ServeMux) {
	mux.Handle("GET /api/v1/items", h.auth.Require(h.handleListItems))
	mux.Handle("GET /api/v1/items/{id}", h.auth.Require(h.handleItem))
	mux.Handle("POST /api/v1/items/{id}/view", h.auth.Require(h.handleRecordView))
	mux.Handle("GET /api/v1/items/{id}/authors", h.auth.Require(h.handleAuthors))
	mux.Handle("GET /api/v1/items/{id}/file", h.auth.Require(h.handleFile))
	mux.Handle("GET /api/v1/items/{id}/files/{fileID}", h.auth.Require(h.handleFileByID))
	mux.Handle("GET /api/v1/items/{id}/cover", h.auth.Require(h.handleCover))
	mux.Handle("GET /api/v1/items/{id}/progress", h.auth.Require(h.handleGetProgress))
	mux.Handle("PUT /api/v1/items/{id}/progress", h.auth.Require(h.handlePutProgress))
	mux.Handle("GET /api/v1/progress/recent", h.auth.Require(h.handleRecent))
}

func (h *Handlers) handleItem(w http.ResponseWriter, r *http.Request, u auth.User) {
	it, ok := h.authorized(w, r, u)
	if !ok {
		return
	}

	files, err := h.files(r, it.ID)
	if err != nil {
		h.fail(w, "list files", err)
		return
	}

	prog, has, err := progress.Get(r.Context(), h.db, u.ID, it.ID)
	if err != nil {
		h.fail(w, "get progress", err)
		return
	}

	authors, err := h.authors(r, it.ID)
	if err != nil {
		h.fail(w, "authors", err)
		return
	}

	out := map[string]any{
		"item": map[string]any{
			"id":         it.ID,
			"library_id": it.LibraryID,
			"kind":       it.Kind,
			"path":       it.Path,
			"title":      it.Title,
			"year":       it.Year,
			"missing":    it.Missing,
		},
		"files":     files,
		"has_cover": h.hasCover(r, it),
		"authors":   authors,
	}
	if has {
		out["progress"] = prog
	}
	httpx.WriteJSON(w, http.StatusOK, out)
}

// authors returns the credited people for an item.
func (h *Handlers) authors(r *http.Request, itemID int64) ([]string, error) {
	rows, err := h.db.QueryContext(r.Context(), `
		SELECT p.name FROM item_people ip
		JOIN people p ON p.id = ip.person_id
		WHERE ip.item_id = ? ORDER BY ip.ord`, itemID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	out := []string{}
	for rows.Next() {
		var name string
		if err := rows.Scan(&name); err != nil {
			return nil, err
		}
		out = append(out, name)
	}
	return out, rows.Err()
}

func (h *Handlers) handleFile(w http.ResponseWriter, r *http.Request, u auth.User) {
	it, ok := h.authorized(w, r, u)
	if !ok {
		return
	}

	// Toolbar download vs inline. Inline is the default for readers.
	disposition := "inline"
	if r.URL.Query().Get("download") == "1" {
		disposition = "attachment"
		allowed, err := auth.CanAccessLibrary(r.Context(), h.db, u, it.LibraryID)
		if err != nil || !allowed {
			httpx.WriteError(w, http.StatusForbidden, "download not permitted")
			return
		}
	}
	w.Header().Set("Content-Disposition", disposition+`; filename="`+sanitizeFilename(it.Path)+`"`)

	if err := stream.ServeFile(w, r, it.AbsPath()); err != nil {
		if errors.Is(err, os.ErrNotExist) {
			httpx.WriteError(w, http.StatusNotFound, "file is not available")
			return
		}
		if errors.Is(err, stream.ErrNotAFile) {
			httpx.WriteError(w, http.StatusBadRequest, "item is not a file")
			return
		}
		h.fail(w, "serve file", err)
		return
	}
}

// handleFileByID streams one specific file of an item, for multi-file items
// such as audiobook chapters or album tracks.
func (h *Handlers) handleFileByID(w http.ResponseWriter, r *http.Request, u auth.User) {
	it, ok := h.authorized(w, r, u)
	if !ok {
		return
	}

	fileID, err := strconv.ParseInt(r.PathValue("fileID"), 10, 64)
	if err != nil || fileID <= 0 {
		httpx.WriteError(w, http.StatusBadRequest, "invalid file id")
		return
	}

	// Confirm the file belongs to this item, so an item id cannot be paired
	// with another item's file id.
	f, err := catalog.FileByID(r.Context(), h.db, it.ID, fileID)
	if errors.Is(err, catalog.ErrNotFound) {
		httpx.WriteError(w, http.StatusNotFound, "file not found")
		return
	}
	if err != nil {
		h.fail(w, "load file", err)
		return
	}

	abs := filepath.Join(it.RootPath, filepath.FromSlash(f.Path))
	w.Header().Set("Content-Disposition", "inline")
	if err := stream.ServeFile(w, r, abs); err != nil {
		if errors.Is(err, os.ErrNotExist) {
			httpx.WriteError(w, http.StatusNotFound, "file is not available")
			return
		}
		h.fail(w, "serve file", err)
		return
	}
}

func (h *Handlers) handleCover(w http.ResponseWriter, r *http.Request, u auth.User) {
	it, ok := h.authorized(w, r, u)
	if !ok {
		return
	}

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

func (h *Handlers) handleGetProgress(w http.ResponseWriter, r *http.Request, u auth.User) {
	it, ok := h.authorized(w, r, u)
	if !ok {
		return
	}
	prog, found, err := progress.Get(r.Context(), h.db, u.ID, it.ID)
	if err != nil {
		h.fail(w, "get progress", err)
		return
	}
	if !found {
		httpx.WriteJSON(w, http.StatusOK, map[string]any{"progress": nil})
		return
	}
	httpx.WriteJSON(w, http.StatusOK, map[string]any{"progress": prog})
}

func (h *Handlers) handlePutProgress(w http.ResponseWriter, r *http.Request, u auth.User) {
	it, ok := h.authorized(w, r, u)
	if !ok {
		return
	}

	var req struct {
		FileID   int64   `json:"file_id"`
		Position *int64  `json:"position"`
		Duration int64   `json:"duration"`
		Percent  float64 `json:"percent"`
		Finished bool    `json:"finished"`
	}
	if err := httpx.DecodeJSON(r, &req); err != nil {
		httpx.WriteError(w, http.StatusBadRequest, err.Error())
		return
	}

	p := progress.Progress{
		ItemID:   it.ID,
		FileID:   req.FileID,
		Kind:     it.Kind,
		Duration: req.Duration,
		Percent:  req.Percent,
		Finished: req.Finished,
	}
	if req.Position != nil {
		p.Position = *req.Position
	}

	saved, err := progress.Put(r.Context(), h.db, u.ID, p)
	if errors.Is(err, progress.ErrNoFile) {
		httpx.WriteError(w, http.StatusConflict, "item has no file to track progress against")
		return
	}
	if err != nil {
		h.fail(w, "save progress", err)
		return
	}
	httpx.WriteJSON(w, http.StatusOK, map[string]any{"progress": saved})
}

func (h *Handlers) handleRecent(w http.ResponseWriter, r *http.Request, u auth.User) {
	items, err := progress.RecentlyUpdated(r.Context(), h.db, u.ID, 20)
	if err != nil {
		h.fail(w, "recent progress", err)
		return
	}
	httpx.WriteJSON(w, http.StatusOK, map[string]any{"progress": items})
}

// handleRecordView increments the user's view count for an item.
//
// The counting SQL lives in internal/home, which owns the shelves that read
// these numbers back; only the item-scoped route stays here.
func (h *Handlers) handleRecordView(w http.ResponseWriter, r *http.Request, u auth.User) {
	it, ok := h.authorized(w, r, u)
	if !ok {
		return
	}
	views, err := home.RecordView(r.Context(), h.db, u.ID, it.ID)
	if err != nil {
		h.fail(w, "record view", err)
		return
	}
	httpx.WriteJSON(w, http.StatusOK, map[string]any{"item_id": it.ID, "views": views})
}

// handleAuthors returns the people credited on an item.
func (h *Handlers) handleAuthors(w http.ResponseWriter, r *http.Request, u auth.User) {
	it, ok := h.authorized(w, r, u)
	if !ok {
		return
	}
	authors, err := h.authors(r, it.ID)
	if err != nil {
		h.fail(w, "authors", err)
		return
	}
	httpx.WriteJSON(w, http.StatusOK, map[string]any{"authors": authors})
}

// ── helpers ────────────────────────────────────────────────────────────

// inClause builds "?,?,?" plus the matching args for an IN list.
//
// Duplicated from internal/home on purpose: a browse list is an item resource,
// and importing the home-screen package to borrow a query-string helper would
// invert the dependency for three lines.
func inClause(ids []int64) (string, []any) {
	placeholders := make([]string, len(ids))
	args := make([]any, len(ids))
	for i, id := range ids {
		placeholders[i] = "?"
		args[i] = id
	}
	return strings.Join(placeholders, ","), args
}

// authorized loads an item and confirms the caller may read its library.
// On failure it has already written the response.
//
// The load and the access check both live in catalog.LoadFor, so this package
// no longer carries its own copy of the "may this user read this item" rule.
func (h *Handlers) authorized(w http.ResponseWriter, r *http.Request, u auth.User) (Item, bool) {
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil || id <= 0 {
		httpx.WriteError(w, http.StatusBadRequest, "invalid item id")
		return Item{}, false
	}

	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 Item{}, false
	}
	if err != nil {
		h.fail(w, "load item", err)
		return Item{}, false
	}
	return it, true
}

// files returns an item's physical files with their ffprobe codec facts.
//
// The shape is catalog.File, whose JSON tags are frozen by MediaFile in
// web/src/lib/api.ts. The server reports what is IN the file and never
// transcodes; each client decides whether it can direct-play it.
func (h *Handlers) files(r *http.Request, itemID int64) ([]catalog.File, error) {
	return catalog.Files(r.Context(), h.db, itemID)
}

func (h *Handlers) hasCover(r *http.Request, it Item) bool {
	var n int
	_ = h.db.QueryRowContext(r.Context(),
		`SELECT count(*) FROM assets WHERE item_id = ? AND role = 'cover'`, it.ID).Scan(&n)
	return n > 0
}

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")
}

// sanitizeFilename strips characters that break a Content-Disposition header.
func sanitizeFilename(name string) string {
	out := make([]rune, 0, len(name))
	for _, r := range name {
		switch {
		case r == '"' || r == '\\' || r == '\n' || r == '\r':
			out = append(out, '_')
		default:
			out = append(out, r)
		}
	}
	return string(out)
}