// kafka — a privacy-respecting metasearch engine
// Copyright (C) 2026-present metamorphosis-dev
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

package httpapi

import (
	"context"
	"encoding/json"
	"net/http"
	"strings"

	"github.com/metamorphosis-dev/kafka/internal/contracts"
	"github.com/metamorphosis-dev/kafka/internal/search"
	"github.com/metamorphosis-dev/kafka/internal/views"
)

type Handler struct {
	searchSvc          *search.Service
	autocompleteSvc    func(ctx context.Context, query string) ([]string, error)
	sourceURL          string
}

func NewHandler(searchSvc *search.Service, autocompleteSuggestions func(ctx context.Context, query string) ([]string, error), sourceURL string) *Handler {
	return &Handler{
		searchSvc:       searchSvc,
		autocompleteSvc: autocompleteSuggestions,
		sourceURL:       sourceURL,
	}
}

func (h *Handler) Healthz(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write([]byte("OK"))
}

// Index renders the homepage with the search box.
func (h *Handler) Index(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/" {
		http.NotFound(w, r)
		return
	}
	if err := views.RenderIndex(w, h.sourceURL); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

// OpenSearch serves the OpenSearch description XML.
func (h *Handler) OpenSearch(baseURL string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		xml, err := views.OpenSearchXML(baseURL)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/opensearchdescription+xml; charset=utf-8")
		w.Write(xml)
	}
}

func (h *Handler) Search(w http.ResponseWriter, r *http.Request) {
	q := r.FormValue("q")
	format := r.FormValue("format")

	// For HTML format with no query, redirect to homepage.
	if q == "" && (format == "" || format == "html") {
		http.Redirect(w, r, "/", http.StatusFound)
		return
	}

	req, err := search.ParseSearchRequest(r)
	if err != nil {
		if format == "html" || format == "" {
			pd := views.PageData{SourceURL: h.sourceURL, Query: q}
			if views.IsHTMXRequest(r) {
				views.RenderSearchFragment(w, pd)
			} else {
				views.RenderSearch(w, pd)
			}
			return
		}
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	resp, err := h.searchSvc.Search(r.Context(), req)
	if err != nil {
		if req.Format == contracts.FormatHTML {
			pd := views.PageData{SourceURL: h.sourceURL, Query: req.Query}
			if views.IsHTMXRequest(r) {
				views.RenderSearchFragment(w, pd)
			} else {
				views.RenderSearch(w, pd)
			}
			return
		}
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	if req.Format == contracts.FormatHTML {
		pd := views.FromResponse(resp, req.Query, req.Pageno,
		r.FormValue("category"), r.FormValue("time"), r.FormValue("type"))
		if err := views.RenderSearchAuto(w, r, pd); err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
		return
	}

	if err := search.WriteSearchResponse(w, req.Format, resp); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

// Autocompleter returns search suggestions for the given query.
func (h *Handler) Autocompleter(w http.ResponseWriter, r *http.Request) {
	query := strings.TrimSpace(r.FormValue("q"))
	if query == "" {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	suggestions, err := h.autocompleteSvc(r.Context(), query)
	if err != nil {
		// Return empty list on error rather than an error status.
		suggestions = []string{}
	}

	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	_ = json.NewEncoder(w).Encode(suggestions)
}

// Preferences handles GET and POST for the preferences page.
func (h *Handler) Preferences(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/preferences" {
		http.NotFound(w, r)
		return
	}
	if r.Method == "POST" {
		// Preferences are stored in localStorage on the client via JavaScript.
		// This handler exists only for form submission completeness.
		http.Redirect(w, r, "/preferences", http.StatusFound)
		return
	}
	if err := views.RenderPreferences(w, h.sourceURL); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}
