package marketing

import (
	"fmt"
	"time"
)

// PresetID identifies a seasonal content-calendar preset.
type PresetID string

const (
	PresetBlackFriday PresetID = "black_friday"
	PresetChristmas   PresetID = "christmas"
)

// CampaignStructureKey is stored on export_feeds.template JSON (no migration).
const CampaignStructureKey = "_campaign"

// Preset is a dated seasonal window for preparing an export feed.
type Preset struct {
	ID          PresetID `json:"id"`
	Name        string   `json:"name"`
	Description string   `json:"description"`
	StartDate   string   `json:"start_date"`
	EndDate     string   `json:"end_date"`
	Year        int      `json:"year"`
}

// StructureMeta is persisted under template._campaign.
type StructureMeta struct {
	PresetID    PresetID `json:"presetId"`
	Name        string   `json:"name"`
	StartDate   string   `json:"startDate"`
	EndDate     string   `json:"endDate"`
	Year        int      `json:"year"`
	PreparedAt  string   `json:"preparedAt"`
}

func pad2(n int) string {
	return fmt.Sprintf("%02d", n)
}

func toISODate(t time.Time) string {
	return fmt.Sprintf("%s-%s-%s", pad2(t.Year()), pad2(int(t.Month())), pad2(t.Day()))
}

// BlackFridayDate returns Black Friday (day after US Thanksgiving) in UTC date parts.
func BlackFridayDate(year int) time.Time {
	nov1 := time.Date(year, time.November, 1, 0, 0, 0, 0, time.UTC)
	dow := int(nov1.Weekday()) // Sunday=0
	firstThursday := 1 + ((4 - dow + 7) % 7)
	fourthThursday := firstThursday + 21
	return time.Date(year, time.November, fourthThursday+1, 0, 0, 0, 0, time.UTC)
}

// ResolvePreset returns date window for a preset id and year.
func ResolvePreset(id PresetID, year int) (Preset, error) {
	if year < 2000 || year > 2100 {
		return Preset{}, ClientMsg("invalid year")
	}
	switch id {
	case PresetBlackFriday:
		bf := BlackFridayDate(year)
		start := bf.AddDate(0, 0, -7)
		end := bf.AddDate(0, 0, 3)
		return Preset{
			ID:          id,
			Name:        "Black Friday",
			Description: "Promo window around Black Friday — prepare a Google Shopping-style export feed.",
			StartDate:   toISODate(start),
			EndDate:     toISODate(end),
			Year:        year,
		}, nil
	case PresetChristmas:
		return Preset{
			ID:          PresetChristmas,
			Name:        "Christmas",
			Description: "Holiday catalog push from Dec 1 through Boxing Day.",
			StartDate:   toISODate(time.Date(year, time.December, 1, 0, 0, 0, 0, time.UTC)),
			EndDate:     toISODate(time.Date(year, time.December, 26, 0, 0, 0, 0, time.UTC)),
			Year:        year,
		}, nil
	default:
		return Preset{}, ClientMsg("preset_id must be black_friday or christmas")
	}
}

// ListPresets returns Black Friday + Christmas for the year.
func ListPresets(year int) []Preset {
	bf, _ := ResolvePreset(PresetBlackFriday, year)
	xmas, _ := ResolvePreset(PresetChristmas, year)
	return []Preset{bf, xmas}
}

// DefaultCampaignMappings are Google Shopping-ish CSV column → product field sources.
func DefaultCampaignMappings() map[string]string {
	return map[string]string{
		"id":                      "product_id",
		"title":                   "processed_name",
		"description":             "processed_description",
		"link":                    "attr.url",
		"image_link":              "attr.image",
		"availability":            "attr.availability",
		"price":                   "attr.price",
		"brand":                   "attr.brand",
		"gtin":                    "gtin",
		"google_product_category": "category",
		"condition":               "attr.condition",
	}
}