package notify

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

// DiscordNotifier posts to a Discord incoming webhook. Body is rendered
// as a single embed so Discord shows a colored sidebar matching event
// severity. Discord rejects empty content+embeds; we always include the
// embed so that never happens.
type DiscordNotifier struct {
	NameStr    string
	WebhookURL string
	HTTP       *http.Client
}

func NewDiscord(name, webhookURL string) *DiscordNotifier {
	return &DiscordNotifier{
		NameStr:    name,
		WebhookURL: webhookURL,
		HTTP:       &http.Client{Timeout: 10 * time.Second},
	}
}

func (d *DiscordNotifier) Name() string { return d.NameStr }

type discordPayload struct {
	Embeds []discordEmbed `json:"embeds"`
}

type discordEmbed struct {
	Title       string `json:"title,omitempty"`
	Description string `json:"description,omitempty"`
	URL         string `json:"url,omitempty"`
	Color       int    `json:"color,omitempty"`
}

func (d *DiscordNotifier) Send(ctx context.Context, ev Event) error {
	if d.WebhookURL == "" {
		return fmt.Errorf("discord: no webhook_url configured")
	}
	payload := discordPayload{Embeds: []discordEmbed{{
		Title:       ev.Title,
		Description: ev.Body,
		URL:         ev.URL,
		Color:       discordColor(ev.Severity),
	}}}
	buf, err := json.Marshal(payload)
	if err != nil {
		return err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, d.WebhookURL, bytes.NewReader(buf))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	resp, err := d.HTTP.Do(req)
	if err != nil {
		return err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode >= 300 {
		b, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("discord: %d: %s", resp.StatusCode, strings.TrimSpace(string(b)))
	}
	return nil
}

// discordColor returns the embed sidebar color for each severity.
// Values are standard Discord decimal color codes.
func discordColor(s Severity) int {
	switch s {
	case SeverityCritical:
		return 0xE74C3C // red
	case SeverityWarning:
		return 0xF1C40F // yellow
	default:
		return 0x2ECC71 // green
	}
}