package proxy

import (
	"bytes"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"strings"

	"github.com/elazarl/goproxy"

	"git.gulenok.ru/greenhaze/gaslight/internal/capture"
	"git.gulenok.ru/greenhaze/gaslight/internal/config"
	"git.gulenok.ru/greenhaze/gaslight/internal/domain"
	"git.gulenok.ru/greenhaze/gaslight/internal/rewrite"
	"git.gulenok.ru/greenhaze/gaslight/internal/tlsutil"
)

func Run(cfg config.Config) error {
	if err := os.MkdirAll(cfg.OutputDir, 0o755); err != nil {
		return fmt.Errorf("failed to create output directory: %w", err)
	}

	caCert, err := tlsutil.LoadCACert(cfg.CertPath, cfg.KeyPath)
	if err != nil {
		return fmt.Errorf("failed to load CA certificate/key: %w", err)
	}
	goproxy.GoproxyCa = *caCert

	imageSaver := capture.NewImageSaver(cfg.OutputDir)
	rewriter := rewrite.NewProcessor(rewrite.DefaultQuestionTestHook)

	p := goproxy.NewProxyHttpServer()
	p.Verbose = false
	p.OnRequest().HandleConnect(goproxy.AlwaysMitm)
	p.OnResponse().DoFunc(func(resp *http.Response, _ *goproxy.ProxyCtx) *http.Response {
		if resp == nil || resp.Request == nil || resp.Body == nil {
			return resp
		}

		if !domain.IsMckoDomain(resp.Request.Host) {
			return resp
		}

		original, err := io.ReadAll(resp.Body)
		_ = resp.Body.Close()
		if err != nil {
			log.Printf("read body failed for %s: %v", resp.Request.URL.String(), err)
			return resp
		}

		contentType := strings.ToLower(resp.Header.Get("Content-Type"))
		if capture.IsImageResponse(contentType, resp.Request.URL.Path) {
			if err := imageSaver.Save(resp, original); err != nil {
				log.Printf("save image failed for %s: %v", resp.Request.URL.String(), err)
			}
			setResponseBody(resp, original)
			return resp
		}

		if !rewrite.IsHTMLResponse(contentType) {
			setResponseBody(resp, original)
			return resp
		}

		modified, err := rewriter.RewriteIfNeeded(resp.Request, resp.Header.Get("Content-Encoding"), original)
		if err != nil {
			log.Printf("html rewrite failed for %s: %v", resp.Request.URL.String(), err)
			setResponseBody(resp, original)
			return resp
		}

		setResponseBody(resp, modified)
		return resp
	})

	log.Printf("proxy listening on %s", cfg.ListenAddr)
	return http.ListenAndServe(cfg.ListenAddr, p)
}

func setResponseBody(resp *http.Response, body []byte) {
	resp.Body = io.NopCloser(bytes.NewReader(body))
	resp.ContentLength = int64(len(body))
	resp.Header.Set("Content-Length", fmt.Sprint(len(body)))
}