package httpapi

import (
	"errors"
	"fmt"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/szabadpalya/api/internal/hu"
	"github.com/szabadpalya/api/internal/ogimage"
	"github.com/szabadpalya/api/internal/store"
)

// ogImage serves the per-campaign share card. A crawler fetches this once per
// share and caches it for a long time, so an hour of staleness is fine and the
// header keeps us from redrawing on every Facebook refresh.
func (s *Server) ogImage(c *gin.Context) {
	campaign, err := s.store.GetCampaignBySlug(c.Request.Context(), c.Param("slug"))
	if errors.Is(err, store.ErrNotFound) {
		png, err := ogimage.Fallback()
		if err != nil {
			s.fail(c, err)
			return
		}
		c.Header("Cache-Control", "public, max-age=300")
		c.Data(http.StatusOK, "image/png", png)
		return
	}
	if err != nil {
		s.fail(c, err)
		return
	}

	pct := hu.ProgressPct(campaign.Raised, campaign.Goal)
	// The bar is scaled so an overfunded campaign still shows its 100% mark
	// rather than a bar that is simply full.
	scale := max(100, pct)
	card := ogimage.Card{
		Title:    campaign.Title,
		Category: campaign.Category,
		Creator:  campaign.Creator.Name + " · " + campaign.Creator.Location,
		Raised:   hu.FormatHUF(campaign.Raised),
		GoalNote: fmt.Sprintf("a %s-os célból", hu.FormatHUF(campaign.Goal)),
		Percent:  fmt.Sprintf("%d%%", pct),
		Fraction: float64(min(pct, 100)) / float64(scale),
		Backers:  hu.FormatNumber(campaign.Backers) + " támogató",
		Deadline: deadlineLabel(campaign, s.store.Budapest),
	}
	if pct > 100 {
		card.Over = float64(pct-100) / float64(scale)
	}

	png, err := ogimage.Render(card)
	if err != nil {
		s.fail(c, err)
		return
	}
	c.Header("Cache-Control", "public, max-age=3600")
	c.Data(http.StatusOK, "image/png", png)
}

func deadlineLabel(campaign *store.Campaign, loc *time.Location) string {
	if campaign.Status == "lezart" {
		return "lezárult"
	}
	return fmt.Sprintf("%d nap van hátra", hu.DaysLeft(campaign.EndsAt, loc, time.Now()))
}