package api

import (
	"encoding/json"
	"log"
	"net/http"
	"strings"
	"time"

	"bookmarkmanager/backend/internal/httpmw"
	"bookmarkmanager/backend/internal/store"
)

// Handler serves the userscript-facing JSON bookmark API.
type Handler struct {
	Store *store.Store
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if v != nil {
		if err := json.NewEncoder(w).Encode(v); err != nil {
			log.Printf("encode response: %v", err)
		}
	}
}

// List returns all bookmarks of the acting Reader. GET /bookmarks
func (h *Handler) List(w http.ResponseWriter, r *http.Request) {
	items, err := h.Store.List(httpmw.ReaderID(r))
	if err != nil {
		log.Printf("list: %v", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	writeJSON(w, http.StatusOK, items)
}

// Put upserts one bookmark. PUT /bookmarks/{key}
func (h *Handler) Put(w http.ResponseWriter, r *http.Request) {
	key := r.PathValue("key")
	if key == "" {
		http.Error(w, "missing key", http.StatusBadRequest)
		return
	}

	var b store.Bookmark
	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 1<<16)).Decode(&b); err != nil {
		http.Error(w, "invalid JSON body", http.StatusBadRequest)
		return
	}
	// A body may carry a cover, and it is discarded here rather than
	// rejected: every installed userscript still sends one, and ADR-0004's
	// compatibility argument depends on those scripts continuing to work. The
	// Cover is acquired server-side (ADR-0007), so the field is permanently
	// inert - not pending removal, and not a value any later code should
	// start reading.
	b.Cover = ""

	// Path key is authoritative; derive site/series_id from it when the body
	// omits them so the stored row is always self-consistent.
	b.Key = key
	if b.Site == "" || b.SeriesID == "" {
		if site, series, ok := strings.Cut(key, ":"); ok {
			if b.Site == "" {
				b.Site = site
			}
			if b.SeriesID == "" {
				b.SeriesID = series
			}
		}
	}

	// An empty status is "no opinion" and Upsert keeps the stored bucket.
	// Finishing a series is a web-UI decision, so the JSON API refuses it
	// rather than trusting every client to leave it alone.
	switch b.Status {
	case "", store.StatusReading, store.StatusArchived:
	case store.StatusFinished:
		http.Error(w, "status "+store.StatusFinished+" can only be set from the web UI",
			http.StatusBadRequest)
		return
	default:
		http.Error(w, "invalid status", http.StatusBadRequest)
		return
	}

	// Same rule as status: empty means "keep the stored value". An unknown
	// value is a client bug, not something to silently coerce to manga.
	switch b.Kind {
	case "", store.KindManga, store.KindNovel:
	default:
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid kind"})
		return
	}

	// Candidate timestamp, not a decision: Upsert keeps the stored one unless
	// reading progress actually moved. Any client value is ignored.
	b.UpdatedAt = time.Now().UnixMilli()

	stored, err := h.Store.Upsert(httpmw.ReaderID(r), b)
	if err != nil {
		log.Printf("upsert: %v", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	// Echo the stored row: clients adopt this as their cached copy, so it must
	// carry the authoritative updated_at rather than the candidate above.
	writeJSON(w, http.StatusOK, stored)
}

// Delete removes one bookmark. DELETE /bookmarks/{key}
func (h *Handler) Delete(w http.ResponseWriter, r *http.Request) {
	key := r.PathValue("key")
	if key == "" {
		http.Error(w, "missing key", http.StatusBadRequest)
		return
	}
	if err := h.Store.Delete(httpmw.ReaderID(r), key); err != nil {
		log.Printf("delete: %v", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// Healthz answers the unauthenticated liveness check. GET /healthz
func Healthz(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write([]byte("ok"))
}

// Cover serves stored cover bytes. GET /covers/{address}
//
// Public on purpose: the userscript renders these on Sites the deployment
// does not control, where no credential of ours may be sent, and the address
// is the SHA-256 of a URL the Site already publishes (ADR-0007). An unknown
// address is a 404 rather than an error - "no Cover yet" is a normal state,
// and the clients fall back to their placeholder.
func (h *Handler) Cover(w http.ResponseWriter, r *http.Request) {
	body, contentType, ok, err := h.Store.CoverByAddress(r.PathValue("address"))
	if err != nil {
		log.Printf("cover: %v", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	if !ok {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", contentType)
	// Content-addressed, so the bytes at this URL can never change. Public
	// rather than private: no credential gates the route.
	w.Header().Set("Cache-Control", "public, max-age=604800, immutable")
	_, _ = w.Write(body)
}