package handlers

import (
	"encoding/json"
	"errors"
	"log"
	"net/http"
	"thamanyah/discovery/internal/api"
	"thamanyah/discovery/internal/db/repositories"
)

// GetVideo serves the catalogue's copy of one video.
//
//	@Summary		Get a catalogued video
//	@Description	Returns the catalogue's copy of a video: what a reader needs to show and play it. A video appears here only after the CMS has announced it as ready, so a video that is still transcoding — or one the CMS never made ready — is a 404.
//	@Tags			videos
//	@Produce		json
//	@Param			id	path		string	true	"Video id, as issued by the CMS"
//	@Success		200	{object}	api.Video
//	@Failure		404	{object}	api.ProblemDetails
//	@Failure		500	{object}	api.ProblemDetails
//	@Router			/api/videos/{id} [get]
func GetVideo(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")

	video, err := repositories.VideoRepo.GetVideoByID(r.Context(), id)
	if errors.Is(err, repositories.ErrVideoNotFound) {
		writeProblem(w, http.StatusNotFound, "Video Not In The Catalogue",
			"No video with that id is in the catalogue. A video appears here once the CMS announces it as ready, so one that is still being transcoded is not here yet.")
		return
	}
	if err != nil {
		log.Printf("Something Went Wrong Loading A Catalogued Video: id=%q: %s", id, err)
		writeProblem(w, http.StatusInternalServerError, "Something Went Wrong Loading The Catalogue",
			"The video could not be read from the database. This is a server-side fault and the request was not processed; retrying in a few moments may succeed.")
		return
	}

	// Translated field by field rather than returned as-is: models.Video is the
	// row, api.Video is the published schema, and neither should drag the other
	// along when it changes.
	writeJSON(w, http.StatusOK, api.Video{
		ID:          video.ID,
		Title:       video.Title,
		PlaybackURL: video.PlaybackURL,
		// Never null on the wire: a video with no categories has an empty
		// list, which is a different thing from "unknown".
		Categories: append([]string{}, video.Categories...),
	})
}

const (
	// searchPageSize is how many videos a search returns when the caller does
	// not say. Small enough to keep the common request cheap.
	searchPageSize = 20

	// maxSearchPageSize is the largest page the catalogue will build, however
	// big a page the caller asks for. The endpoint is read constantly, and a
	// page size is a request for work: without a ceiling, one client asking
	// for the whole catalogue in a single response makes every other reader
	// wait behind it.
	//
	// Asking for more is not an error — the page is simply capped, and the
	// cursor still reaches the rest — because a client that wants everything
	// is doing something legitimate, just not in one request.
	maxSearchPageSize = 100
)

// SearchVideos serves the catalogue's lexical search.
//
// It is served on QUERY rather than GET or POST: a search is safe and
// idempotent, which POST is not, but its parameters are a structured document
// that does not belong in a query string. QUERY says both. It is specified in
// draft-ietf-httpbis-safe-method-w-body, not in RFC 9110 — still a draft, so
// expect intermediaries that have never heard of it. Note it also cannot be
// expressed in the generated OpenAPI spec — Swagger 2.0 and OpenAPI 3.x define a fixed set of
// per-method fields with no slot for QUERY, and swag rejects the annotation
// outright — so this endpoint is deliberately absent from /swagger and
// documented here instead.
func SearchVideos(w http.ResponseWriter, r *http.Request) {
	var request api.SearchRequest

	if err := json.NewDecoder(r.Body).Decode(&request); err != nil {
		writeProblem(w, http.StatusBadRequest, "Malformed Search",
			"The request body could not be read as JSON. Send a JSON object describing what to search for; an empty object browses the whole catalogue.")
		return
	}

	limit := request.Limit
	if limit <= 0 {
		limit = searchPageSize
	}
	if limit > maxSearchPageSize {
		limit = maxSearchPageSize
	}

	found, next, err := repositories.VideoRepo.SearchVideos(r.Context(), request.Title, request.Categories, limit, request.Cursor)
	if errors.Is(err, repositories.ErrInvalidCursor) {
		writeProblem(w, http.StatusBadRequest, "Malformed Search Cursor",
			"The cursor could not be read. Send back the nextCursor from a previous search unchanged, or omit it to start from the first page.")
		return
	}
	if err != nil {
		log.Printf("Something Went Wrong Searching The Catalogue: title=%q: %s", request.Title, err)
		writeProblem(w, http.StatusInternalServerError, "Something Went Wrong Searching The Catalogue",
			"The catalogue could not be searched. This is a server-side fault and the request was not processed; retrying in a few moments may succeed.")
		return
	}

	// Translated field by field, for the same reason GetVideo does it: the row
	// and the published schema are different things.
	videos := make([]api.Video, 0, len(found))
	for _, v := range found {
		videos = append(videos, api.Video{
			ID:          v.ID,
			Title:       v.Title,
			PlaybackURL: v.PlaybackURL,
			Categories:  append([]string{}, v.Categories...),
		})
	}

	writeJSON(w, http.StatusOK, api.SearchResults{Videos: videos, NextCursor: next})
}