package web

import (
	"fmt"
	"fuj-management/go/internal/web/api"
	"html/template"
	"log/slog"
	"net/http"
	"net/url"
	"strconv"
)

// PageData is the view model passed to every HTML template.
type PageData struct {
	Active string
	Build  BuildInfo
}

// AdultsPageData is the view model for the /adults HTML page.
type AdultsPageData struct {
	PageData
	Data  api.AdultsResponse
	Error string
}

// JuniorsPageData is the view model for the /juniors HTML page.
type JuniorsPageData struct {
	PageData
	Data  api.JuniorsResponse
	Error string
}

// Renderer parses and executes HTML templates from the embedded FS.
type Renderer struct {
	tmpls map[string]*template.Template
}

var pageNames = []string{"adults", "juniors", "payments", "sync", "flush_cache"}

// qrHref builds the /qr query URL for a single-month Pay button.
// rawMonth is "YYYY-MM"; it is converted to "MM/YYYY" in the QR message.
func qrHref(account string, amount int, name, rawMonth string) string {
	// Convert "YYYY-MM" → "MM/YYYY" to match Python's showPayQR JS.
	if len(rawMonth) == 7 && rawMonth[4] == '-' {
		rawMonth = rawMonth[5:] + "/" + rawMonth[:4]
	}
	msg := name + ": " + rawMonth
	return "/qr?" + url.Values{
		"account": {account},
		"amount":  {strconv.Itoa(amount)},
		"message": {msg},
	}.Encode()
}

// qrHrefAll builds the /qr query URL for a Pay-All button.
// rawPeriods is the "+" -joined MM/YYYY string from MemberRow.RawUnpaidPeriods.
func qrHrefAll(account string, amount int, name, rawPeriods string) string {
	msg := name + ": " + rawPeriods
	return "/qr?" + url.Values{
		"account": {account},
		"amount":  {strconv.Itoa(amount)},
		"message": {msg},
	}.Encode()
}

var tmplFuncs = template.FuncMap{
	"qrHref":    qrHref,
	"qrHrefAll": qrHrefAll,
}

// NewRenderer parses all templates from the embedded FS.
// A parse failure should be treated as a startup-time fatal error.
func NewRenderer() (*Renderer, error) {
	tmpls := make(map[string]*template.Template, len(pageNames))
	for _, name := range pageNames {
		t, err := template.New("").Funcs(tmplFuncs).ParseFS(templateFS,
			"templates/base.tmpl",
			"templates/partials/nav.tmpl",
			"templates/partials/footer.tmpl",
			"templates/"+name+".tmpl",
		)
		if err != nil {
			return nil, fmt.Errorf("parse template %q: %w", name, err)
		}
		tmpls[name] = t
	}
	return &Renderer{tmpls: tmpls}, nil
}

// Render executes the named template with data, writing to w.
func (r *Renderer) Render(w http.ResponseWriter, name string, data any) {
	t, ok := r.tmpls[name]
	if !ok {
		http.Error(w, "template not found: "+name, http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := t.ExecuteTemplate(w, "base", data); err != nil {
		slog.Error("render template", "name", name, "err", err)
	}
}