package discord

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

	"sanity/internal/backup"
)

type Client struct {
	webhookURL   string
	httpClient   *http.Client
	serverName   string
	notifyRoleID string
}

type webhookPayload struct {
	Content         string          `json:"content,omitempty"`
	AllowedMentions allowedMentions `json:"allowed_mentions,omitempty"`
	Embeds          []embed         `json:"embeds"`
}

type allowedMentions struct {
	Roles []string `json:"roles,omitempty"`
}

type embed struct {
	Title       string       `json:"title"`
	Description string       `json:"description,omitempty"`
	Color       int          `json:"color"`
	Timestamp   string       `json:"timestamp,omitempty"`
	Fields      []embedField `json:"fields,omitempty"`
	Footer      *embedFooter `json:"footer,omitempty"`
}

type embedField struct {
	Name   string `json:"name"`
	Value  string `json:"value"`
	Inline bool   `json:"inline"`
}

type embedFooter struct {
	Text string `json:"text"`
}

func New(serverName string, webhookURL string, notifyRoleID string, timeout time.Duration) *Client {
	return &Client{
		serverName:   serverName,
		webhookURL:   webhookURL,
		httpClient:   &http.Client{Timeout: timeout},
		notifyRoleID: notifyRoleID,
	}
}

func (c *Client) SendSuccess(ctx context.Context, result backup.Result, interval time.Duration) error {
	fields := []embedField{
		{Name: "Server", Value: c.serverName, Inline: true},
		{Name: "Source", Value: result.SourceFile, Inline: false},
		{Name: "Artifact", Value: result.ArtifactPath, Inline: false},
		{Name: "Artifact size", Value: formatBytes(result.SizeBytes), Inline: true},
		{Name: "Backup dir total", Value: formatOptionalBytes(result.TotalBackupDirSizeBytes), Inline: true},
		{Name: "Duration", Value: result.Duration.Round(time.Millisecond).String(), Inline: true},
		{Name: "Next run", Value: formatSummaryInterval(interval), Inline: true},
		{Name: "Timestamp", Value: formatDiscordTime(result.Timestamp), Inline: true},
	}
	return c.send(ctx, webhookPayload{Embeds: []embed{{
		Title:       fmt.Sprintf("sanity backup successful - %s", c.serverName),
		Description: "A scheduled backup completed successfully.",
		Color:       0x27AE60,
		Fields:      fields,
		Footer:      &embedFooter{Text: fmt.Sprintf("sanity - %s", c.serverName)},
	}}})
}

func (c *Client) SendFailure(ctx context.Context, timestamp time.Time, reason string, sourceFile string, outputDir string, totalBackupDirSizeBytes int64) error {
	fields := []embedField{
		{Name: "Server", Value: c.serverName, Inline: true},
		{Name: "Source", Value: sourceFile, Inline: false},
		{Name: "Output dir", Value: outputDir, Inline: false},
		{Name: "Backup dir total", Value: formatOptionalBytes(totalBackupDirSizeBytes), Inline: true},
		{Name: "Timestamp", Value: formatDiscordTime(timestamp), Inline: true},
		{Name: "Reason", Value: reason, Inline: false},
	}
	payload := webhookPayload{Embeds: []embed{{
		Title:       fmt.Sprintf("sanity backup failed - %s", c.serverName),
		Description: "A scheduled backup run failed.",
		Color:       0xE74C3C,
		Timestamp:   timestamp.Format(time.RFC3339),
		Fields:      fields,
	}}}
	if c.notifyRoleID != "" {
		payload.Content = fmt.Sprintf("<@&%s>", c.notifyRoleID)
		payload.AllowedMentions = allowedMentions{Roles: []string{c.notifyRoleID}}
	}
	return c.send(ctx, payload)
}

func formatDiscordTime(timestamp time.Time) string {
	unixSeconds := timestamp.Unix()
	return fmt.Sprintf("<t:%d:f>", unixSeconds)
}

func formatSummaryInterval(interval time.Duration) string {
	if interval%time.Hour == 0 {
		return fmt.Sprintf("%dh", interval/time.Hour)
	}
	if interval%time.Minute == 0 {
		return fmt.Sprintf("%dm", interval/time.Minute)
	}
	return interval.String()
}

func formatOptionalBytes(sizeBytes int64) string {
	if sizeBytes < 0 {
		return "unknown"
	}
	return formatBytes(sizeBytes)
}

func formatBytes(sizeBytes int64) string {
	const (
		kib = 1024
		mib = 1024 * 1024
		gib = 1024 * 1024 * 1024
		tib = 1024 * 1024 * 1024 * 1024
	)
	if sizeBytes <= 0 {
		return "0 B"
	}
	if sizeBytes < kib {
		return fmt.Sprintf("%d B", sizeBytes)
	}
	if sizeBytes < mib {
		return fmt.Sprintf("%.2f KB", float64(sizeBytes)/kib)
	}
	if sizeBytes < gib {
		return fmt.Sprintf("%.2f MB", float64(sizeBytes)/mib)
	}
	if sizeBytes < tib {
		return fmt.Sprintf("%.2f GB", float64(sizeBytes)/gib)
	}
	return fmt.Sprintf("%.2f TB", float64(sizeBytes)/tib)
}

func (c *Client) send(ctx context.Context, payload webhookPayload) error {
	buffer := &bytes.Buffer{}
	if err := json.NewEncoder(buffer).Encode(payload); err != nil {
		return err
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.webhookURL, buffer)
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return fmt.Errorf("discord webhook returned %s", resp.Status)
	}
	return nil
}