package discord

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

	"heartbeat/internal/alerts"
	"heartbeat/internal/metrics"
)

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) SendSummary(ctx context.Context, sample metrics.Sample, summaryInterval time.Duration) error {
	fields := []embedField{
		{Name: "Server", Value: c.serverName, Inline: true},
		{Name: "Generated", Value: formatSummaryTime(sample.Timestamp), Inline: true},
		{Name: "Uptime", Value: formatUptime(sample.UptimeSeconds), Inline: true},
		{Name: "CPU", Value: fmt.Sprintf("Now: %.1f%%\n15m: %.1f%%\n12h: %.1f%%", sample.CPUCurrentPercent, sample.CPUAvg15mPercent, sample.CPUAvg12hPercent), Inline: true},
		{Name: "Load", Value: fmt.Sprintf("1m: %.2f\n5m: %.2f\n15m/core: %.2f", sample.Load1, sample.Load5, sample.LoadPerCore), Inline: true},
		{Name: "Memory", Value: fmt.Sprintf("RAM: %.1f%%\nSwap: %.1f%%", sample.MemoryUsedPercent, sample.SwapUsedPercent), Inline: true},
		{Name: "Disk /", Value: fmt.Sprintf("Used: %.1f%%\nFree: %.1f GB\nInodes: %.1f%%", sample.RootUsedPercent, sample.RootFreeGB, sample.InodeUsedPercent), Inline: true},
		{Name: "Network", Value: fmt.Sprintf("RX: %s\nTX: %s", formatRate(sample.RXBytesPerSecond), formatRate(sample.TXBytesPerSecond)), Inline: true},
		{Name: "Processes", Value: fmt.Sprintf("Count: %d", sample.ProcessCount), Inline: true},
		{Name: "Sites", Value: formatSiteStatuses(sample.Sites), Inline: false},
	}
	return c.send(ctx, webhookPayload{Embeds: []embed{{
		Title:       fmt.Sprintf("heartbeat (%s) - %s", formatSummaryIntervalHours(summaryInterval), c.serverName),
		Description: "Scheduled server health snapshot.",
		Color:       0x2D9CDB,
		Fields:      fields,
		Footer:      &embedFooter{Text: formatSummaryFooter(c.serverName)},
	}}})
}

func (c *Client) SendEvent(ctx context.Context, sample metrics.Sample, event alerts.Event) error {
	fields := []embedField{
		{Name: "Server", Value: c.serverName, Inline: true},
		{Name: "Severity", Value: string(event.Severity), Inline: true},
		{Name: "Timestamp", Value: formatEventTime(sample.Timestamp), Inline: true},
	}
	payload := webhookPayload{Embeds: []embed{{
		Title:       event.Title,
		Description: event.Body,
		Color:       colorForSeverity(event.Severity),
		Timestamp:   sample.Timestamp.Format(time.RFC3339),
		Fields:      fields,
	}}}
	if c.notifyRoleID != "" && (event.Severity == alerts.SeverityWarning || event.Severity == alerts.SeverityCritical) {
		payload.Content = fmt.Sprintf("<@&%s>", c.notifyRoleID)
		payload.AllowedMentions = allowedMentions{Roles: []string{c.notifyRoleID}}
	}
	return c.send(ctx, payload)
}

func formatUptime(totalSeconds uint64) string {
	duration := time.Duration(totalSeconds) * time.Second
	days := duration / (24 * time.Hour)
	duration -= days * 24 * time.Hour
	hours := duration / time.Hour
	duration -= hours * time.Hour
	minutes := duration / time.Minute
	if days > 0 {
		return fmt.Sprintf("%dd %dh %dm", days, hours, minutes)
	}
	return fmt.Sprintf("%dh %dm", hours, minutes)
}

func formatSiteStatuses(sites []metrics.SiteStatus) string {
	if len(sites) == 0 {
		return "No site checks configured"
	}
	parts := make([]string, 0, len(sites))
	for _, site := range sites {
		status := "UP"
		detail := fmt.Sprintf("%d in %s", site.StatusCode, site.Latency.Round(time.Millisecond))
		if !site.Healthy {
			status = "DOWN"
			detail = site.ErrorMessage
		}
		parts = append(parts, fmt.Sprintf("%s: %s (%s)", site.Name, status, detail))
	}
	return strings.Join(parts, "\n")
}

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

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

func formatSummaryFooter(serverName string) string {
	return fmt.Sprintf("heartbeat - %s", serverName)
}

func formatSummaryIntervalHours(interval time.Duration) string {
	if interval%time.Hour == 0 {
		return fmt.Sprintf("%dh", interval/time.Hour)
	}
	return fmt.Sprintf("%.2fh", interval.Hours())
}

func formatRate(bytesPerSecond float64) string {
	if bytesPerSecond < 0 {
		return "n/a"
	}
	if bytesPerSecond < 1024 {
		return fmt.Sprintf("%.0f B/s", bytesPerSecond)
	}
	kib := bytesPerSecond / 1024
	if kib < 1024 {
		return fmt.Sprintf("%.2f KB/s", kib)
	}
	mib := kib / 1024
	return fmt.Sprintf("%.2f MB/s", mib)
}

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
}

func colorForSeverity(severity alerts.Severity) int {
	switch severity {
	case alerts.SeverityCritical:
		return 0xE74C3C
	case alerts.SeverityWarning:
		return 0xF39C12
	default:
		return 0x27AE60
	}
}