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package forge

import (
	"compress/gzip"
	"context"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"strings"
	"time"
)

func isSmart(r *http.Request, rest string) bool {
	switch rest {
	case "info/refs":
		return r.URL.Query().Get("service") != ""
	case "git-upload-pack", "git-receive-pack":
		return r.Method == "POST"
	}
	return false
}

func (s *Server) basicUser(r *http.Request) (User, string, bool) {
	name, secret, ok := r.BasicAuth()
	if !ok {
		return User{}, "", false
	}
	if u, scope, ok := s.store.UserByToken(name, secret); ok {
		return u, scope, true
	}
	u, ok := s.store.CheckPassword(name, secret)
	return u, scopeAll, ok
}

func (s *Server) smart(w http.ResponseWriter, r *http.Request, owner User, name, rest string) {
	repo, err := s.store.RepoByPath(owner.Name, name)
	if err != nil {
		var viewer *User
		if u, _, ok := s.basicUser(r); ok {
			viewer = &u
		}
		segment, _, _ := strings.Cut(strings.TrimPrefix(r.URL.Path, "/~"+owner.Name+"/"), "/")
		if !s.redirectMoved(w, r, owner.Name, segment, viewer, http.StatusPermanentRedirect) {
			http.Error(w, "repository not found", 404)
		}
		return
	}
	service := r.URL.Query().Get("service")
	if rest != "info/refs" {
		service = rest
	}
	if service != "git-upload-pack" && service != "git-receive-pack" {
		http.Error(w, "unsupported service", 403)
		return
	}
	needAuth := service == "git-receive-pack" || repo.Private
	var pusher User
	writer := false
	if needAuth {
		ip := clientIP(r)
		if s.limiter.blocked(ip) {
			http.Error(w, "too many failed attempts", 429)
			return
		}
		u, scope, ok := s.basicUser(r)
		if !ok || !s.store.CanRead(repo, &u) {
			if _, _, given := r.BasicAuth(); given {
				s.limiter.fail(ip)
			}
			w.Header().Set("WWW-Authenticate", `Basic realm="`+s.host+`"`)
			http.Error(w, "authentication required", 401)
			return
		}
		if service == "git-receive-pack" && scope != scopeAll {
			http.Error(w, "this token is scoped to "+scope+" and cannot push to repositories", 403)
			return
		}
		pusher, writer = u, s.store.CanWrite(repo, &u)
	}
	if service == "git-receive-pack" && !hooksReady(s.root) {
		http.Error(w, "pushes are unavailable right now", 503)
		return
	}
	if service == "git-receive-pack" && repo.Archived {
		http.Error(w, "repository is archived and read only", 403)
		return
	}
	if service == "git-receive-pack" {
		if over, used, quota := overQuota(s.root, repo.Owner.Name); over {
			http.Error(w, quotaMessage(used, quota), 403)
			return
		}
	}
	var recv, env []string
	limit := int64(0)
	if service == "git-receive-pack" {
		recv = append(receiveArgs(s.root), pushLimit(s.root, repo.Owner.Name, writer)...)
		env = receiveEnv(repo, pusher)
		if over, used, quota := overQuota(s.root, repo.Owner.Name); quota > 0 && !over {
			limit = quota - used + 1<<20
		}
		if !writer && (limit == 0 || limit > guestPush+1<<20) {
			limit = guestPush + 1<<20
		}
	}
	s.gitService(w, r, s.repoDir(repo), service, rest, recv, env, limit)
}

func (s *Server) gitService(w http.ResponseWriter, r *http.Request, dir, service, rest string, recv, env []string, limit int64) {
	w.Header().Set("Cache-Control", "no-cache")
	ctx, cancel := context.WithTimeout(r.Context(), 10*time.Minute)
	defer cancel()
	if rest == "info/refs" {
		argv := []string{strings.TrimPrefix(service, "git-"), "--stateless-rpc", "--advertise-refs", dir}
		if service == "git-receive-pack" {
			argv = append(recv, argv...)
		}
		cmd := exec.CommandContext(ctx, "git", argv...)
		cmd.Env = []string{"HOME=/nonexistent", "PATH=" + os.Getenv("PATH")}
		out, err := cmd.Output()
		if err != nil {
			http.Error(w, "git failed", 500)
			return
		}
		w.Header().Set("Content-Type", "application/x-"+service+"-advertisement")
		fmt.Fprintf(w, "%04x# service=%s\n0000", len(service)+15, service)
		w.Write(out)
		return
	}
	var body io.Reader = r.Body
	if r.Header.Get("Content-Encoding") == "gzip" {
		gz, err := gzip.NewReader(r.Body)
		if err != nil {
			http.Error(w, "bad gzip", 400)
			return
		}
		defer gz.Close()
		body = gz
	}
	argv := []string{strings.TrimPrefix(service, "git-"), "--stateless-rpc", dir}
	if service == "git-receive-pack" {
		argv = append(recv, argv...)
		if limit > 0 {
			body = io.LimitReader(body, limit)
		}
	}
	cmd := exec.CommandContext(ctx, "git", argv...)
	cmd.Stdin = body
	cmd.Env = []string{"GIT_PROTOCOL=" + r.Header.Get("Git-Protocol"), "HOME=/nonexistent", "PATH=" + os.Getenv("PATH")}
	if service == "git-receive-pack" {
		cmd.Env = append(cmd.Env, env...)
	}
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		http.Error(w, "git failed", 500)
		return
	}
	if err := cmd.Start(); err != nil {
		http.Error(w, "git failed", 500)
		return
	}
	w.Header().Set("Content-Type", "application/x-"+service+"-result")
	w.WriteHeader(200)
	flusher, _ := w.(http.Flusher)
	buf := make([]byte, 32*1024)
	for {
		n, err := stdout.Read(buf)
		if n > 0 {
			w.Write(buf[:n])
			if flusher != nil {
				flusher.Flush()
			}
		}
		if err != nil {
			break
		}
	}
	cmd.Wait()
}