package handler

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"github.com/gofiber/fiber/v3"
	"gopkg.in/yaml.v3"

	"github.com/peterqiu0516/sub-store/internal/model"
	"github.com/peterqiu0516/sub-store/internal/service"
	"github.com/peterqiu0516/sub-store/internal/util"
)

func (d *Deps) HandleEgressInfo(c fiber.Ctx) error {
	var node model.ProxyNode
	if err := json.Unmarshal(c.Body(), &node); err != nil {
		return failed(c, "Invalid JSON", 400)
	}
	if getStringValue(node["server"]) == "" {
		node["server"] = getStringValue(node["address"])
	}
	if getStringValue(node["name"]) == "" {
		node["name"] = "PROXY"
	}

	cacheKey := service.EgressCacheKey(node)
	if entry, ok := d.CacheRepo.SafeGet(cacheKey); ok {
		var cached map[string]any
		if json.Unmarshal([]byte(entry.Content), &cached) == nil {
			cached["cached"] = true
			return success(c, cached)
		}
	}

	latencyMs, latencyErr := probeServerPortLatency(node, 5*time.Second)
	port, err := freeLocalPort()
	if err != nil {
		return failed(c, err.Error(), 500)
	}
	configData, err := buildEgressProbeConfig(node, port)
	if err != nil {
		return failed(c, err.Error(), 400)
	}

	info, err := runEgressProbe(configData, port)
	if err != nil {
		info = fiber.Map{"egressError": err.Error()}
	}
	if latencyMs >= 0 {
		info["latencyMs"] = latencyMs
	}
	if latencyErr != "" {
		info["latencyError"] = latencyErr
	}
	info["cached"] = false
	if data, err := json.Marshal(info); err == nil {
		ttl := int(d.Cfg.Fetcher.EgressCacheTTL.Seconds())
		if ttl <= 0 {
			ttl = 86400 // 24h default
		}
		d.CacheRepo.SafePut(cacheKey, string(data), nil, ttl)
	}
	return success(c, info)
}

func (d *Deps) addCachedEgressInfo(nodes []model.ProxyNode) []model.ProxyNode {
	for _, node := range nodes {
		entry, ok := d.CacheRepo.SafeGet(service.EgressCacheKey(node))
		if !ok {
			continue
		}
		var cached map[string]any
		if json.Unmarshal([]byte(entry.Content), &cached) != nil {
			continue
		}
		for _, key := range []string{"egressIp", "country", "countryCode", "region", "city", "isp", "flag", "latencyMs", "latencyError", "egressError"} {
			if v, ok := cached[key]; ok {
				node[key] = v
			}
		}
		node["cached"] = true
	}
	return nodes
}

func probeServerPortLatency(node model.ProxyNode, timeout time.Duration) (int64, string) {
	server := getStringValue(node["server"])
	port := toIntSafe(node["port"])
	if server == "" || port <= 0 {
		return -1, "missing server or port"
	}
	start := time.Now()
	conn, err := net.DialTimeout("tcp", net.JoinHostPort(server, fmt.Sprint(port)), timeout)
	if err != nil {
		return -1, err.Error()
	}
	_ = conn.Close()
	return time.Since(start).Milliseconds(), ""
}

func buildEgressProbeConfig(node model.ProxyNode, port int) ([]byte, error) {
	probeNode := model.ProxyNode{}
	for k, v := range node {
		probeNode[k] = v
	}
	probeNode["name"] = "PROXY"

	// Build a minimal mihomo (Clash Meta) config with the probe node as the
	// only proxy. mihomo natively supports xhttp and other Clash transports.
	proxyYaml, err := yaml.Marshal(probeNode)
	if err != nil {
		return nil, fmt.Errorf("Failed to marshal proxy node: %w", err)
	}

	config := fmt.Sprintf(`mixed-port: %d
allow-lan: false
mode: rule
log-level: warning
proxies:
- %s
proxy-groups:
- name: PROXY-GROUP
  type: select
  proxies:
  - PROXY
rules:
- MATCH,PROXY-GROUP
`, port, strings.ReplaceAll(strings.TrimSuffix(string(proxyYaml), "\n"), "\n", "\n  "))

	return []byte(config), nil
}

func runEgressProbe(configData []byte, port int) (fiber.Map, error) {
	mihomo, err := exec.LookPath("mihomo")
	if err != nil {
		return nil, fmt.Errorf("mihomo executable not found")
	}
	dir, err := os.MkdirTemp("", "sub-store-egress-*")
	if err != nil {
		return nil, err
	}
	defer os.RemoveAll(dir)

	configPath := filepath.Join(dir, "config.yaml")
	if err := os.WriteFile(configPath, configData, 0o600); err != nil {
		return nil, err
	}

	ctx, cancel := context.WithTimeout(context.Background(), 25*time.Second)
	defer cancel()
	cmd := exec.CommandContext(ctx, mihomo, "-f", configPath)
	var stderr bytes.Buffer
	cmd.Stderr = &stderr
	if err := cmd.Start(); err != nil {
		return nil, err
	}
	defer func() {
		cancel()
		_ = cmd.Wait()
	}()

	if err := waitTCP("127.0.0.1", port, 5*time.Second); err != nil {
		msg := strings.TrimSpace(stderr.String())
		if msg != "" {
			return nil, fmt.Errorf("%s", msg)
		}
		return nil, err
	}

	proxyURL, _ := url.Parse(fmt.Sprintf("http://127.0.0.1:%d", port))
	client := &http.Client{
		Timeout: 15 * time.Second,
		Transport: &http.Transport{
			Proxy: http.ProxyURL(proxyURL),
		},
	}
	resp, err := client.Get("https://ipwho.is/?lang=en")
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	body, _ := io.ReadAll(io.LimitReader(resp.Body, util.MaxFlowRespBytes))

	var data map[string]any
	if err := json.Unmarshal(body, &data); err != nil {
		return nil, fmt.Errorf("Invalid egress info response")
	}
	if success, ok := data["success"].(bool); ok && !success {
		msg := getStringValue(data["message"])
		if msg == "" {
			msg = "Egress info lookup failed"
		}
		return nil, fmt.Errorf("%s", msg)
	}
	connection, _ := data["connection"].(map[string]any)
	flagObj, _ := data["flag"].(map[string]any)
	return fiber.Map{
		"egressIp":    data["ip"],
		"country":     data["country"],
		"countryCode": data["country_code"],
		"region":      data["region"],
		"city":        data["city"],
		"isp":         connection["isp"],
		"flag":        flagObj["emoji"],
	}, nil
}

func freeLocalPort() (int, error) {
	l, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		return 0, err
	}
	defer l.Close()
	return l.Addr().(*net.TCPAddr).Port, nil
}

func waitTCP(host string, port int, timeout time.Duration) error {
	deadline := time.Now().Add(timeout)
	addr := fmt.Sprintf("%s:%d", host, port)
	for time.Now().Before(deadline) {
		conn, err := net.DialTimeout("tcp", addr, 200*time.Millisecond)
		if err == nil {
			conn.Close()
			return nil
		}
		time.Sleep(100 * time.Millisecond)
	}
	return fmt.Errorf("Timed out waiting for mihomo")
}