// Package httpapi предоставляет HTTP API и веб-UI (server-rendered).
//
// Тонкий транспорт над ядром: приём идёт в ingest, команды (cancel/retry) —
// в worker, чтение — в store. В v1 без авторизации (доверенная LAN).
package httpapi

import (
	"context"
	"encoding/json"
	"errors"
	"html/template"
	"log/slog"
	"net/http"
	"net/url"
	"strconv"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"

	"git.vakhrushev.me/av/jellybit/internal/ingest"
	"git.vakhrushev.me/av/jellybit/internal/store"
	"git.vakhrushev.me/av/jellybit/web"
)

// Ingestor принимает загрузку (ingest.Service).
type Ingestor interface {
	Ingest(ctx context.Context, req ingest.Request) (ingest.Result, error)
}

// Commander исполняет команды над задачей (worker.Worker).
type Commander interface {
	Cancel(ctx context.Context, id int64) error
	Retry(ctx context.Context, id int64) error
}

// Reader читает задачи (store.Store).
type Reader interface {
	ListDownloads(ctx context.Context) ([]store.Download, error)
	GetDownload(ctx context.Context, id int64) (*store.Download, error)
}

// Deps — зависимости транспорта.
type Deps struct {
	Logger    *slog.Logger
	Ingestor  Ingestor
	Commander Commander
	Reader    Reader
	Reviewer  Reviewer
}

type server struct {
	deps   Deps
	index  *template.Template
	review *template.Template
}

// NewRouter собирает HTTP-обработчик сервиса.
func NewRouter(d Deps) (http.Handler, error) {
	index, err := template.ParseFS(web.FS, "templates/index.html")
	if err != nil {
		return nil, err
	}
	review, err := template.New("review.html").
		Funcs(template.FuncMap{"add": func(a, b int) int { return a + b }}).
		ParseFS(web.FS, "templates/review.html")
	if err != nil {
		return nil, err
	}
	s := &server{deps: d, index: index, review: review}

	r := chi.NewRouter()
	r.Use(middleware.RequestID)
	r.Use(middleware.Recoverer)
	r.Use(requestLogger(d.Logger))

	r.Get("/healthz", handleHealthz)

	// Веб-UI.
	r.Get("/", s.handleIndex)
	r.Post("/ui/downloads", s.handleUIAdd)
	r.Post("/ui/downloads/{id}/cancel", s.handleUICancel)

	// Веб-UI: ревью раскладки.
	r.Get("/review/{id}", s.handleReview)
	r.Post("/ui/downloads/{id}/apply", s.handleApply)
	r.Post("/ui/downloads/{id}/refine", s.handleRefine)
	r.Post("/ui/downloads/{id}/type", s.handleSetType)
	r.Post("/ui/downloads/{id}/ignore", s.handleIgnore)
	r.Post("/ui/downloads/{id}/defer", s.handleDefer)
	r.Post("/ui/downloads/{id}/undo", s.handleUndo)

	// REST API.
	r.Route("/api", func(r chi.Router) {
		r.Get("/downloads", s.handleAPIList)
		r.Post("/downloads", s.handleAPIAdd)
		r.Get("/downloads/{id}", s.handleAPIGet)
		r.Post("/downloads/{id}/cancel", s.handleAPICancel)
		r.Post("/downloads/{id}/retry", s.handleAPIRetry)
	})

	return r, nil
}

func handleHealthz(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

// --- Веб-UI ---

type indexView struct {
	Error     string
	Downloads []downloadView
}

type downloadView struct {
	ID         int64
	Source     string
	Infohash   string
	Context    string
	State      string
	Error      string
	Terminal   bool
	Reviewable bool // review/deferred — есть экран ревью
	Undoable   bool // done — можно откатить раскладку
}

func (s *server) handleIndex(w http.ResponseWriter, r *http.Request) {
	downloads, err := s.deps.Reader.ListDownloads(r.Context())
	if err != nil {
		s.deps.Logger.Error("list downloads", "err", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	view := indexView{Error: r.URL.Query().Get("err")}
	for _, d := range downloads {
		view.Downloads = append(view.Downloads, toView(d))
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := s.index.Execute(w, view); err != nil {
		s.deps.Logger.Error("render index", "err", err)
	}
}

func (s *server) handleUIAdd(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		redirectErr(w, r, "не удалось разобрать форму")
		return
	}
	_, err := s.deps.Ingestor.Ingest(r.Context(), ingest.Request{
		Source:  r.PostForm.Get("source"),
		Context: r.PostForm.Get("context"),
	})
	if err != nil {
		redirectErr(w, r, err.Error())
		return
	}
	http.Redirect(w, r, "/", http.StatusSeeOther)
}

func (s *server) handleUICancel(w http.ResponseWriter, r *http.Request) {
	id, err := pathID(r)
	if err != nil {
		redirectErr(w, r, "некорректный id")
		return
	}
	if err := s.deps.Commander.Cancel(r.Context(), id); err != nil {
		redirectErr(w, r, err.Error())
		return
	}
	http.Redirect(w, r, "/", http.StatusSeeOther)
}

// --- REST API ---

type downloadDTO struct {
	ID         int64  `json:"id"`
	SourceType string `json:"source_type"`
	Infohash   string `json:"infohash,omitempty"`
	Context    string `json:"context,omitempty"`
	State      string `json:"state"`
	ErrorCode  string `json:"error_code,omitempty"`
	ErrorMsg   string `json:"error_msg,omitempty"`
	CreatedAt  string `json:"created_at"`
	UpdatedAt  string `json:"updated_at"`
}

type addRequest struct {
	Source  string `json:"source"`
	Context string `json:"context"`
}

type addResponse struct {
	ID           int64  `json:"id"`
	Infohash     string `json:"infohash"`
	State        string `json:"state"`
	Deduplicated bool   `json:"deduplicated"`
}

func (s *server) handleAPIList(w http.ResponseWriter, r *http.Request) {
	downloads, err := s.deps.Reader.ListDownloads(r.Context())
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, errJSON(err))
		return
	}
	out := make([]downloadDTO, 0, len(downloads))
	for _, d := range downloads {
		out = append(out, toDTO(d))
	}
	writeJSON(w, http.StatusOK, out)
}

func (s *server) handleAPIGet(w http.ResponseWriter, r *http.Request) {
	id, err := pathID(r)
	if err != nil {
		writeJSON(w, http.StatusBadRequest, errJSON(err))
		return
	}
	d, err := s.deps.Reader.GetDownload(r.Context(), id)
	if err != nil {
		writeJSON(w, http.StatusNotFound, errJSON(err))
		return
	}
	writeJSON(w, http.StatusOK, toDTO(*d))
}

func (s *server) handleAPIAdd(w http.ResponseWriter, r *http.Request) {
	var req addRequest
	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 1<<16)).Decode(&req); err != nil {
		writeJSON(w, http.StatusBadRequest, errJSON(err))
		return
	}
	res, err := s.deps.Ingestor.Ingest(r.Context(), ingest.Request{Source: req.Source, Context: req.Context})
	if err != nil {
		writeJSON(w, http.StatusBadRequest, errJSON(err))
		return
	}
	status := http.StatusCreated
	if res.Deduplicated {
		status = http.StatusOK
	}
	writeJSON(w, status, addResponse{
		ID:           res.DownloadID,
		Infohash:     res.Infohash,
		State:        string(res.State),
		Deduplicated: res.Deduplicated,
	})
}

func (s *server) handleAPICancel(w http.ResponseWriter, r *http.Request) {
	s.apiCommand(w, r, s.deps.Commander.Cancel)
}

func (s *server) handleAPIRetry(w http.ResponseWriter, r *http.Request) {
	s.apiCommand(w, r, s.deps.Commander.Retry)
}

func (s *server) apiCommand(w http.ResponseWriter, r *http.Request, cmd func(context.Context, int64) error) {
	id, err := pathID(r)
	if err != nil {
		writeJSON(w, http.StatusBadRequest, errJSON(err))
		return
	}
	if err := cmd(r.Context(), id); err != nil {
		writeJSON(w, http.StatusConflict, errJSON(err))
		return
	}
	d, err := s.deps.Reader.GetDownload(r.Context(), id)
	if err != nil {
		writeJSON(w, http.StatusOK, map[string]int64{"id": id})
		return
	}
	writeJSON(w, http.StatusOK, toDTO(*d))
}

// --- helpers ---

func toDTO(d store.Download) downloadDTO {
	return downloadDTO{
		ID:         d.ID,
		SourceType: string(d.SourceType),
		Infohash:   d.Infohash.String,
		Context:    d.Context,
		State:      string(d.State),
		ErrorCode:  d.ErrorCode.String,
		ErrorMsg:   d.ErrorMsg.String,
		CreatedAt:  d.CreatedAt,
		UpdatedAt:  d.UpdatedAt,
	}
}

func toView(d store.Download) downloadView {
	return downloadView{
		ID:         d.ID,
		Source:     shorten(d.SourceRef, 64),
		Infohash:   d.Infohash.String,
		Context:    d.Context,
		State:      string(d.State),
		Error:      d.ErrorMsg.String,
		Terminal:   d.State.IsTerminal(),
		Reviewable: d.State == store.StateReview || d.State == store.StateDeferred,
		Undoable:   d.State == store.StateDone,
	}
}

func shorten(s string, n int) string {
	if len(s) <= n {
		return s
	}
	return s[:n] + "…"
}

func pathID(r *http.Request) (int64, error) {
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		return 0, errors.New("invalid id")
	}
	return id, nil
}

func redirectErr(w http.ResponseWriter, r *http.Request, msg string) {
	http.Redirect(w, r, "/?err="+url.QueryEscape(msg), http.StatusSeeOther)
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}

func errJSON(err error) map[string]string {
	return map[string]string{"error": err.Error()}
}

// requestLogger пишет структурированный лог по каждому запросу.
func requestLogger(logger *slog.Logger) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			ww := middleware.NewWrapResponseWriter(w, r.ProtoMajor)
			start := time.Now()

			next.ServeHTTP(ww, r)

			logger.Info("http request",
				"method", r.Method,
				"path", r.URL.Path,
				"status", ww.Status(),
				"bytes", ww.BytesWritten(),
				"duration_ms", time.Since(start).Milliseconds(),
				"request_id", middleware.GetReqID(r.Context()),
			)
		})
	}
}