package osi

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

	"golang.org/x/net/proxy"
)

type TransportConfig struct {
	Timeout     time.Duration
	Socks5Proxy string
}

type Transport struct {
	client *http.Client
}

func NewTransport(config TransportConfig) (*Transport, error) {
	timeout := config.Timeout
	if timeout <= 0 {
		timeout = 20 * time.Second
	}

	roundTripper := http.DefaultTransport.(*http.Transport).Clone()
	if strings.TrimSpace(config.Socks5Proxy) != "" {
		dialer, err := socks5Dialer(config.Socks5Proxy)
		if err != nil {
			return nil, err
		}
		roundTripper.DialContext = func(ctx context.Context, network, address string) (net.Conn, error) {
			if contextDialer, ok := dialer.(proxy.ContextDialer); ok {
				return contextDialer.DialContext(ctx, network, address)
			}
			return dialer.Dial(network, address)
		}
	}

	return &Transport{client: &http.Client{Timeout: timeout, Transport: roundTripper}}, nil
}

func (t *Transport) PostJSON(ctx context.Context, targetURL string, payload any, headers map[string]string) (int, []byte, error) {
	body, err := json.Marshal(payload)
	if err != nil {
		return 0, nil, fmt.Errorf("marshal json payload: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, targetURL, bytes.NewReader(body))
	if err != nil {
		return 0, nil, fmt.Errorf("build request: %w", err)
	}
	for name, value := range headers {
		req.Header.Set(name, value)
	}
	if req.Header.Get("Content-Type") == "" {
		req.Header.Set("Content-Type", "application/json")
	}

	resp, err := t.client.Do(req)
	if err != nil {
		return 0, nil, err
	}
	defer resp.Body.Close()

	raw, err := io.ReadAll(resp.Body)
	if err != nil {
		return resp.StatusCode, nil, fmt.Errorf("read response body: %w", err)
	}
	return resp.StatusCode, raw, nil
}

func socks5Dialer(rawProxy string) (proxy.Dialer, error) {
	proxyURL, err := normalizeSocks5Proxy(rawProxy)
	if err != nil {
		return nil, err
	}

	dialer, err := proxy.SOCKS5("tcp", proxyURL.Host, nil, proxy.Direct)
	if err != nil {
		return nil, fmt.Errorf("create socks5 dialer: %w", err)
	}
	return dialer, nil
}

func normalizeSocks5Proxy(rawProxy string) (*url.URL, error) {
	rawProxy = strings.TrimSpace(rawProxy)
	if !strings.Contains(rawProxy, "://") {
		rawProxy = "socks5://" + rawProxy
	}

	proxyURL, err := url.Parse(rawProxy)
	if err != nil {
		return nil, fmt.Errorf("parse socks5 proxy: %w", err)
	}
	if proxyURL.Scheme != "socks5" && proxyURL.Scheme != "socks5h" {
		return nil, fmt.Errorf("unsupported proxy scheme %q", proxyURL.Scheme)
	}
	if proxyURL.User != nil {
		return nil, fmt.Errorf("socks5 proxy authentication is not supported yet")
	}
	if _, _, err := net.SplitHostPort(proxyURL.Host); err != nil {
		return nil, fmt.Errorf("invalid socks5 proxy host %q: %w", proxyURL.Host, err)
	}
	return proxyURL, nil
}