package main

import (
	"bytes"
	"context"
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"net"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"syscall"

	"github.com/go-git/go-git/v5/plumbing"

	"github.com/jackc/pgx/v5"

	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing"

	"go.lindenii.runxiyu.org/lindenii-common/ansiec"
)

var (
	err_get_fd    = errors.New("unable to get file descriptor")
	err_get_ucred = errors.New("failed getsockopt")
)

// hooks_handle_connection handles a connection from git_hooks_client via the
// unix socket.
func hooks_handle_connection(conn net.Conn) {
	defer conn.Close()
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// There aren't reasonable cases where someone would run this as
	// another user.
	ucred, err := get_ucred(conn)
	if err != nil {
		if _, err := conn.Write([]byte{1}); err != nil {
			return
		}
		wf_error(conn, "\nUnable to get peer credentials: %v", err)
		return
	}
	if ucred.Uid != uint32(os.Getuid()) {
		if _, err := conn.Write([]byte{1}); err != nil {
			return
		}
		wf_error(conn, "\nUID mismatch")
		return
	}

	cookie := make([]byte, 64)
	_, err = conn.Read(cookie)
	if err != nil {
		if _, err := conn.Write([]byte{1}); err != nil {
			return
		}
		wf_error(conn, "\nFailed to read cookie: %v", err)
		return
	}

	pack_to_hook, ok := pack_to_hook_by_cookie.Load(string(cookie))
	if !ok {
		if _, err := conn.Write([]byte{1}); err != nil {
			return
		}
		wf_error(conn, "\nInvalid handler cookie")
		return
	}

	ssh_stderr := pack_to_hook.session.Stderr()

	ssh_stderr.Write([]byte{'\n'})

	hook_return_value := func() byte {
		var argc64 uint64
		err = binary.Read(conn, binary.NativeEndian, &argc64)
		if err != nil {
			wf_error(ssh_stderr, "Failed to read argc: %v", err)
			return 1
		}
		var args []string
		for i := uint64(0); i < argc64; i++ {
			var arg bytes.Buffer
			for {
				b := make([]byte, 1)
				n, err := conn.Read(b)
				if err != nil || n != 1 {
					wf_error(ssh_stderr, "Failed to read arg: %v", err)
					return 1
				}
				if b[0] == 0 {
					break
				}
				arg.WriteByte(b[0])
			}
			args = append(args, arg.String())
		}

		var stdin bytes.Buffer
		_, err = io.Copy(&stdin, conn)
		if err != nil {
			wf_error(conn, "Failed to read to the stdin buffer: %v", err)
		}

		switch filepath.Base(args[0]) {
		case "pre-receive":
			if pack_to_hook.direct_access {
				return 0
			} else {
				all_ok := true
				for {
					line, err := stdin.ReadString('\n')
					if errors.Is(err, io.EOF) {
						break
					}
					line = line[:len(line)-1]

					old_oid, rest, found := strings.Cut(line, " ")
					if !found {
						wf_error(ssh_stderr, "Invalid pre-receive line: %v", line)
						return 1
					}

					new_oid, ref_name, found := strings.Cut(rest, " ")
					if !found {
						wf_error(ssh_stderr, "Invalid pre-receive line: %v", line)
						return 1
					}

					if strings.HasPrefix(ref_name, "refs/heads/contrib/") {
						if all_zero_num_string(old_oid) { // New branch

							fmt.Fprintln(ssh_stderr, ansiec.Blue + "POK" + ansiec.Reset, ref_name)

							fmt.Fprintln(ssh_stderr, ansiec.Blue+"POK"+ansiec.Reset, ref_name)

							var new_mr_id int
							err = database.QueryRow(ctx,
								"INSERT INTO merge_requests (repo_id, creator, source_ref, status) VALUES ($1, $2, $3, 'open') RETURNING id",
								pack_to_hook.repo_id, pack_to_hook.user_id, strings.TrimPrefix(ref_name, "refs/heads/"),
							).Scan(&new_mr_id)
							if err != nil {
								wf_error(ssh_stderr, "Error creating merge request: %v", err)
								return 1
							}

							fmt.Fprintln(ssh_stderr, ansiec.Blue + "Created merge request at", generate_http_remote_url(pack_to_hook.group_name, pack_to_hook.repo_name) + "/contrib/" + strconv.FormatUint(uint64(new_mr_id), 10) + "/" + ansiec.Reset)

							fmt.Fprintln(ssh_stderr, ansiec.Blue+"Created merge request at", generate_http_remote_url(pack_to_hook.group_name, pack_to_hook.repo_name)+"/contrib/"+strconv.FormatUint(uint64(new_mr_id), 10)+"/"+ansiec.Reset)

						} else { // Existing contrib branch
							var existing_merge_request_user_id int
							err = database.QueryRow(ctx,
								"SELECT COALESCE(creator, 0) FROM merge_requests WHERE source_ref = $1 AND repo_id = $2",
								strings.TrimPrefix(ref_name, "refs/heads/"), pack_to_hook.repo_id,
							).Scan(&existing_merge_request_user_id)
							if err != nil {
								if errors.Is(err, pgx.ErrNoRows) {
									wf_error(ssh_stderr, "No existing merge request for existing contrib branch: %v", err)
								} else {
									wf_error(ssh_stderr, "Error querying for existing merge request: %v", err)
								}
								return 1
							}
							if existing_merge_request_user_id == 0 {
								all_ok = false

								fmt.Fprintln(ssh_stderr, ansiec.Red + "NAK" + ansiec.Reset, ref_name, "(branch belongs to unowned MR)")

								fmt.Fprintln(ssh_stderr, ansiec.Red+"NAK"+ansiec.Reset, ref_name, "(branch belongs to unowned MR)")

								continue
							}

							if existing_merge_request_user_id != pack_to_hook.user_id {
								all_ok = false

								fmt.Fprintln(ssh_stderr, ansiec.Red + "NAK" + ansiec.Reset, ref_name, "(branch belongs another user's MR)")

								fmt.Fprintln(ssh_stderr, ansiec.Red+"NAK"+ansiec.Reset, ref_name, "(branch belongs another user's MR)")

								continue
							}

							repo, err := git.PlainOpen(pack_to_hook.repo_path)
							if err != nil {
								wf_error(ssh_stderr, "Daemon failed to open repo: %v", err)
								return 1
							}

							old_hash := plumbing.NewHash(old_oid)

							old_commit, err := repo.CommitObject(old_hash)

							old_commit, err := pack_to_hook.repo.CommitObject(old_hash)

							if err != nil {
								wf_error(ssh_stderr, "Daemon failed to get old commit: %v", err)
								return 1
							}

							// Potential BUG: I'm not sure if new_commit is guaranteed to be
							// detectable as they haven't been merged into the main repo's
							// objects yet. But it seems to work, and I don't think there's
							// any reason for this to only work intermitently.
							new_hash := plumbing.NewHash(new_oid)

							new_commit, err := repo.CommitObject(new_hash)

							new_commit, err := pack_to_hook.repo.CommitObject(new_hash)

							if err != nil {
								wf_error(ssh_stderr, "Daemon failed to get new commit: %v", err)
								return 1
							}

							is_ancestor, err := old_commit.IsAncestor(new_commit)
							if err != nil {
								wf_error(ssh_stderr, "Daemon failed to check if old commit is ancestor: %v", err)
								return 1
							}

							if !is_ancestor {
								// TODO: Create MR snapshot ref instead
								all_ok = false

								fmt.Fprintln(ssh_stderr, ansiec.Red + "NAK" + ansiec.Reset, ref_name, "(force pushes are not supported yet)")

								fmt.Fprintln(ssh_stderr, ansiec.Red+"NAK"+ansiec.Reset, ref_name, "(force pushes are not supported yet)")

								continue
							}

							fmt.Fprintln(ssh_stderr, ansiec.Blue + "POK" + ansiec.Reset, ref_name)

							fmt.Fprintln(ssh_stderr, ansiec.Blue+"POK"+ansiec.Reset, ref_name)

						}
					} else { // Non-contrib branch
						all_ok = false

						fmt.Fprintln(ssh_stderr, ansiec.Red + "NAK" + ansiec.Reset, ref_name, "(you cannot push to branches outside of contrib/*)")

						fmt.Fprintln(ssh_stderr, ansiec.Red+"NAK"+ansiec.Reset, ref_name, "(you cannot push to branches outside of contrib/*)")

					}
				}

				fmt.Fprintln(ssh_stderr)
				if all_ok {

					fmt.Fprintln(ssh_stderr, "Overall " + ansiec.Green + "ACK" + ansiec.Reset + " (all checks passed)")

					fmt.Fprintln(ssh_stderr, "Overall "+ansiec.Green+"ACK"+ansiec.Reset+" (all checks passed)")

					return 0
				} else {

					fmt.Fprintln(ssh_stderr, "Overall " + ansiec.Red + "NAK" + ansiec.Reset + " (one or more branches failed checks)")

					fmt.Fprintln(ssh_stderr, "Overall "+ansiec.Red+"NAK"+ansiec.Reset+" (one or more branches failed checks)")

					return 1
				}
			}
		default:

			fmt.Fprintln(ssh_stderr, ansiec.Red + "Invalid hook:", args[0] + ansiec.Reset)

			fmt.Fprintln(ssh_stderr, ansiec.Red+"Invalid hook:", args[0]+ansiec.Reset)

			return 1
		}
	}()

	fmt.Fprintln(ssh_stderr)

	_, _ = conn.Write([]byte{hook_return_value})
}

func serve_git_hooks(listener net.Listener) error {
	for {
		conn, err := listener.Accept()
		if err != nil {
			return err
		}
		go hooks_handle_connection(conn)
	}
}

func get_ucred(conn net.Conn) (*syscall.Ucred, error) {
	unix_conn := conn.(*net.UnixConn)
	fd, err := unix_conn.File()
	if err != nil {
		return nil, err_get_fd
	}
	defer fd.Close()

	ucred, err := syscall.GetsockoptUcred(int(fd.Fd()), syscall.SOL_SOCKET, syscall.SO_PEERCRED)
	if err != nil {
		return nil, err_get_ucred
	}
	return ucred, nil
}

func all_zero_num_string(s string) bool {
	for _, r := range s {
		if r != '0' {
			return false
		}
	}
	return true
}

package main

import (
	"errors"
	"fmt"
	"os"
	"os/exec"

	glider_ssh "github.com/gliderlabs/ssh"

	"github.com/go-git/go-git/v5"

	"go.lindenii.runxiyu.org/lindenii-common/cmap"
)

type pack_to_hook_t struct {
	session       glider_ssh.Session

	repo          *git.Repository

	pubkey        string
	direct_access bool
	repo_path     string
	user_id       int
	repo_id       int
	group_name    string
	repo_name     string
}

var pack_to_hook_by_cookie = cmap.Map[string, pack_to_hook_t]{}

// ssh_handle_receive_pack handles attempts to push to repos.
func ssh_handle_receive_pack(session glider_ssh.Session, pubkey string, repo_identifier string) (err error) {
	group_name, repo_name, repo_id, repo_path, direct_access, contrib_requirements, user_type, user_id, err := get_repo_path_perms_from_ssh_path_pubkey(session.Context(), repo_identifier, pubkey)
	if err != nil {
		return err

	}
	repo, err := git.PlainOpen(repo_path)
	if err != nil {
		return err
	}

	repo_config, err := repo.Config()
	if err != nil {
		return err
	}

	repo_config_core := repo_config.Raw.Section("core")
	if repo_config_core == nil {
		return errors.New("Repository has no core section in config")
	}

	hooksPath := repo_config_core.OptionAll("hooksPath")
	if len(hooksPath) != 1 || hooksPath[0] != config.Hooks.Execs {
		return errors.New("Repository has hooksPath set to an unexpected value")

	}

	if !direct_access {
		switch contrib_requirements {
		case "closed":
			if !direct_access {
				return errors.New("You need direct access to push to this repo.")
			}
		case "registered_user":
			if user_type != "registered" {
				return errors.New("You need to be a registered user to push to this repo.")
			}
		case "ssh_pubkey":
			if pubkey == "" {
				return errors.New("You need to have an SSH public key to push to this repo.")
			}
			if user_type == "" {
				user_id, err = add_user_ssh(session.Context(), pubkey)
				if err != nil {
					return err
				}
				fmt.Fprintln(session.Stderr(), "You are now registered as user ID", user_id)
			}
		case "public":
		default:
			panic("unknown contrib_requirements value " + contrib_requirements)
		}
	}

	cookie, err := random_urlsafe_string(16)
	if err != nil {
		fmt.Fprintln(session.Stderr(), "Error while generating cookie:", err)
	}

	fmt.Println(group_name, repo_name)

	pack_to_hook_by_cookie.Store(cookie, pack_to_hook_t{
		session:       session,
		pubkey:        pubkey,
		direct_access: direct_access,
		repo_path:     repo_path,
		user_id:       user_id,
		repo_id:       repo_id,
		group_name:    group_name,
		repo_name:     repo_name,

		repo:          repo,

	})
	defer pack_to_hook_by_cookie.Delete(cookie)
	// The Delete won't execute until proc.Wait returns unless something
	// horribly wrong such as a panic occurs.

	proc := exec.CommandContext(session.Context(), "git-receive-pack", repo_path)
	proc.Env = append(os.Environ(),
		"LINDENII_FORGE_HOOKS_SOCKET_PATH="+config.Hooks.Socket,
		"LINDENII_FORGE_HOOKS_COOKIE="+cookie,
	)
	proc.Stdin = session
	proc.Stdout = session
	proc.Stderr = session.Stderr()

	err = proc.Start()
	if err != nil {
		fmt.Fprintln(session.Stderr(), "Error while starting process:", err)
		return err
	}

	err = proc.Wait()
	if exitError, ok := err.(*exec.ExitError); ok {
		fmt.Fprintln(session.Stderr(), "Process exited with error", exitError.ExitCode())
	} else if err != nil {
		fmt.Fprintln(session.Stderr(), "Error while waiting for process:", err)
	}

	return err
}