// SPDX-License-Identifier: AGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
//
//go:build !linux

package forge

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

	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/object"
	"github.com/jackc/pgx/v5"
	"go.lindenii.runxiyu.org/forge/internal/ansiec"
	"go.lindenii.runxiyu.org/forge/internal/misc"
)

var (
	errGetFD    = errors.New("unable to get file descriptor")
	errGetUcred = errors.New("failed getsockopt")
)

// hooksHandler handles a connection from hookc via the
// unix socket.
func (s *Server) hooksHandler(conn net.Conn) {
	var ctx context.Context
	var cancel context.CancelFunc
	var err error
	var cookie []byte
	var packPass packPass
	var sshStderr io.Writer
	var hookRet byte

	defer conn.Close()
	ctx, cancel = context.WithCancel(context.Background())
	defer cancel()

	// TODO: ucred-like checks

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

	{
		var ok bool
		packPass, ok = s.packPasses.Load(misc.BytesToString(cookie))
		if !ok {
			if _, err = conn.Write([]byte{1}); err != nil {
				return
			}
			writeRedError(conn, "\nInvalid handler cookie")
			return
		}
	}

	sshStderr = packPass.session.Stderr()

	_, _ = sshStderr.Write([]byte{'\n'})

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

		gitEnv := make(map[string]string)
		for {
			var envLine bytes.Buffer
			for {
				nextByte := make([]byte, 1)
				n, err := conn.Read(nextByte)
				if err != nil || n != 1 {
					writeRedError(sshStderr, "Failed to read environment variable: %v", err)
					return 1
				}
				if nextByte[0] == 0 {
					break
				}
				envLine.WriteByte(nextByte[0])
			}
			if envLine.Len() == 0 {
				break
			}
			kv := envLine.String()
			parts := strings.SplitN(kv, "=", 2)
			if len(parts) < 2 {
				writeRedError(sshStderr, "Invalid environment variable line: %v", kv)
				return 1
			}
			gitEnv[parts[0]] = parts[1]
		}

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

		switch filepath.Base(args[0]) {
		case "pre-receive":
			if packPass.directAccess {
				return 0
			}
			allOK := true
			for {
				var line, oldOID, rest, newIOID, refName string
				var found bool
				var oldHash, newHash plumbing.Hash
				var oldCommit, newCommit *object.Commit
				var pushOptCount int

				pushOptCount, err = strconv.Atoi(gitEnv["GIT_PUSH_OPTION_COUNT"])
				if err != nil {
					writeRedError(sshStderr, "Failed to parse GIT_PUSH_OPTION_COUNT: %v", err)
					return 1
				}

				// TODO: Allow existing users (even if they are already federated or registered) to add a federated user ID... though perhaps this should be in the normal SSH interface instead of the git push interface?
				// Also it'd be nice to be able to combine users or whatever
				if packPass.contribReq == "federated" && packPass.userType != "federated" && packPass.userType != "registered" {
					if pushOptCount == 0 {
						writeRedError(sshStderr, "This repo requires contributors to be either federated or registered users. You must supply your federated user ID as a push option. For example, git push -o fedid=sr.ht:runxiyu")
						return 1
					}
					for pushOptIndex := range pushOptCount {
						pushOpt, ok := gitEnv[fmt.Sprintf("GIT_PUSH_OPTION_%d", pushOptIndex)]
						if !ok {
							writeRedError(sshStderr, "Failed to get push option %d", pushOptIndex)
							return 1
						}
						if strings.HasPrefix(pushOpt, "fedid=") {
							fedUserID := strings.TrimPrefix(pushOpt, "fedid=")
							service, username, found := strings.Cut(fedUserID, ":")
							if !found {
								writeRedError(sshStderr, "Invalid federated user identifier %#v does not contain a colon", fedUserID)
								return 1
							}

							ok, err := s.fedauth(ctx, packPass.userID, service, username, packPass.pubkey)
							if err != nil {
								writeRedError(sshStderr, "Failed to verify federated user identifier %#v: %v", fedUserID, err)
								return 1
							}
							if !ok {
								writeRedError(sshStderr, "Failed to verify federated user identifier %#v: you don't seem to be on the list", fedUserID)
								return 1
							}

							break
						}
						if pushOptIndex == pushOptCount-1 {
							writeRedError(sshStderr, "This repo requires contributors to be either federated or registered users. You must supply your federated user ID as a push option. For example, git push -o fedid=sr.ht:runxiyu")
							return 1
						}
					}
				}

				line, err = stdin.ReadString('\n')
				if errors.Is(err, io.EOF) {
					break
				} else if err != nil {
					writeRedError(sshStderr, "Failed to read pre-receive line: %v", err)
					return 1
				}
				line = line[:len(line)-1]

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

				newIOID, refName, found = strings.Cut(rest, " ")
				if !found {
					writeRedError(sshStderr, "Invalid pre-receive line: %v", line)
					return 1
				}

				if strings.HasPrefix(refName, "refs/heads/contrib/") {
					if allZero(oldOID) { // New branch
						fmt.Fprintln(sshStderr, ansiec.Blue+"POK"+ansiec.Reset, refName)
						var newMRLocalID int

						if packPass.userID != 0 {
							err = s.database.QueryRow(ctx,
								"INSERT INTO merge_requests (repo_id, creator, source_ref, status) VALUES ($1, $2, $3, 'open') RETURNING repo_local_id",
								packPass.repoID, packPass.userID, strings.TrimPrefix(refName, "refs/heads/"),
							).Scan(&newMRLocalID)
						} else {
							err = s.database.QueryRow(ctx,
								"INSERT INTO merge_requests (repo_id, source_ref, status) VALUES ($1, $2, 'open') RETURNING repo_local_id",
								packPass.repoID, strings.TrimPrefix(refName, "refs/heads/"),
							).Scan(&newMRLocalID)
						}
						if err != nil {
							writeRedError(sshStderr, "Error creating merge request: %v", err)
							return 1
						}
						mergeRequestWebURL := fmt.Sprintf("%s/contrib/%d/", s.genHTTPRemoteURL(packPass.groupPath, packPass.repoName), newMRLocalID)
						fmt.Fprintln(sshStderr, ansiec.Blue+"Created merge request at", mergeRequestWebURL+ansiec.Reset)

						select {
						case s.ircSendBuffered <- "PRIVMSG #chat :New merge request at " + mergeRequestWebURL:
						default:
							slog.Error("IRC SendQ exceeded")
						}
					} else { // Existing contrib branch
						var existingMRUser int
						var isAncestor bool

						err = s.database.QueryRow(ctx,
							"SELECT COALESCE(creator, 0) FROM merge_requests WHERE source_ref = $1 AND repo_id = $2",
							strings.TrimPrefix(refName, "refs/heads/"), packPass.repoID,
						).Scan(&existingMRUser)
						if err != nil {
							if errors.Is(err, pgx.ErrNoRows) {
								writeRedError(sshStderr, "No existing merge request for existing contrib branch: %v", err)
							} else {
								writeRedError(sshStderr, "Error querying for existing merge request: %v", err)
							}
							return 1
						}
						if existingMRUser == 0 {
							allOK = false
							fmt.Fprintln(sshStderr, ansiec.Red+"NAK"+ansiec.Reset, refName, "(branch belongs to unowned MR)")
							continue
						}

						if existingMRUser != packPass.userID {
							allOK = false
							fmt.Fprintln(sshStderr, ansiec.Red+"NAK"+ansiec.Reset, refName, "(branch belongs another user's MR)")
							continue
						}

						oldHash = plumbing.NewHash(oldOID)

						if oldCommit, err = packPass.repo.CommitObject(oldHash); err != nil {
							writeRedError(sshStderr, "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.
						newHash = plumbing.NewHash(newIOID)
						if newCommit, err = packPass.repo.CommitObject(newHash); err != nil {
							writeRedError(sshStderr, "Daemon failed to get new commit: %v", err)
							return 1
						}

						if isAncestor, err = oldCommit.IsAncestor(newCommit); err != nil {
							writeRedError(sshStderr, "Daemon failed to check if old commit is ancestor: %v", err)
							return 1
						}

						if !isAncestor {
							// TODO: Create MR snapshot ref instead
							allOK = false
							fmt.Fprintln(sshStderr, ansiec.Red+"NAK"+ansiec.Reset, refName, "(force pushes are not supported yet)")
							continue
						}

						fmt.Fprintln(sshStderr, ansiec.Blue+"POK"+ansiec.Reset, refName)
					}
				} else { // Non-contrib branch
					allOK = false
					fmt.Fprintln(sshStderr, ansiec.Red+"NAK"+ansiec.Reset, refName, "(you cannot push to branches outside of contrib/*)")
				}
			}

			fmt.Fprintln(sshStderr)
			if allOK {
				fmt.Fprintln(sshStderr, "Overall "+ansiec.Green+"ACK"+ansiec.Reset+" (all checks passed)")
				return 0
			}
			fmt.Fprintln(sshStderr, "Overall "+ansiec.Red+"NAK"+ansiec.Reset+" (one or more branches failed checks)")
			return 1
		default:
			fmt.Fprintln(sshStderr, ansiec.Red+"Invalid hook:", args[0]+ansiec.Reset)
			return 1
		}
	}()

	fmt.Fprintln(sshStderr)

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

// serveGitHooks handles connections on the specified network listener and
// treats incoming connections as those from git hook handlers by spawning
// sessions. The listener must be a SOCK_STREAM UNIX domain socket. The
// function itself blocks.
func (s *Server) serveGitHooks(listener net.Listener) error {
	for {
		conn, err := listener.Accept()
		if err != nil {
			return err
		}
		go s.hooksHandler(conn)
	}
}

// allZero returns true if all runes in a given string are '0'. The comparison
// is not constant time and must not be used in contexts where time-based side
// channel attacks are a concern.
func allZero(s string) bool {
	for _, r := range s {
		if r != '0' {
			return false
		}
	}
	return true
}

// SPDX-License-Identifier: AGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>

package forge

import (
	"context"
	"errors"
	"io"
	"iter"

	"os"
	"strings"

	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/object"
	"github.com/jackc/pgx/v5/pgtype"
)

// openRepo opens a git repository by group and repo name.
//
// TODO: This should be deprecated in favor of doing it in the relevant
// request/router context in the future, as it cannot cover the nuance of
// fields needed.
func (s *Server) openRepo(ctx context.Context, groupPath []string, repoName string) (repo *git.Repository, description string, repoID int, fsPath string, err error) {
	err = s.database.QueryRow(ctx, `
WITH RECURSIVE group_path_cte AS (
	-- Start: match the first name in the path where parent_group IS NULL
	SELECT
		id,
		parent_group,
		name,
		1 AS depth
	FROM groups
	WHERE name = ($1::text[])[1]
		AND parent_group IS NULL

	UNION ALL

	-- Recurse: join next segment of the path
	SELECT
		g.id,
		g.parent_group,
		g.name,
		group_path_cte.depth + 1
	FROM groups g
	JOIN group_path_cte ON g.parent_group = group_path_cte.id
	WHERE g.name = ($1::text[])[group_path_cte.depth + 1]
		AND group_path_cte.depth + 1 <= cardinality($1::text[])
)
SELECT
	r.filesystem_path,
	COALESCE(r.description, ''),
	r.id
FROM group_path_cte g
JOIN repos r ON r.group_id = g.id
WHERE g.depth = cardinality($1::text[])
	AND r.name = $2
	`, pgtype.FlatArray[string](groupPath), repoName).Scan(&fsPath, &description, &repoID)
	if err != nil {
		return
	}

	repo, err = git.PlainOpen(fsPath)
	return
}

// go-git's tree entries are not friendly for use in HTML templates.
// This struct is a wrapper that is friendlier for use in templating.
type displayTreeEntry struct {
	Name      string
	Mode      string
	Size      uint64
	IsFile    bool
	IsSubtree bool
}

// makeDisplayTree takes git trees of form [object.Tree] and creates a slice of
// [displayTreeEntry] for easier templating.
func makeDisplayTree(tree *object.Tree) (displayTree []displayTreeEntry) {
	for _, entry := range tree.Entries {
		displayEntry := displayTreeEntry{} //exhaustruct:ignore
		var err error
		var osMode os.FileMode

		if osMode, err = entry.Mode.ToOSFileMode(); err != nil {
			displayEntry.Mode = "x---------"
		} else {
			displayEntry.Mode = osMode.String()
		}

		displayEntry.IsFile = entry.Mode.IsFile()

		size, _ := tree.Size(entry.Name)
		displayEntry.Size = uint64(size) //#nosec G115

		displayEntry.Name = strings.TrimPrefix(entry.Name, "/")

		displayTree = append(displayTree, displayEntry)
	}
	return displayTree
}

// commitIterSeqErr creates an [iter.Seq[*object.Commit]] from an
// [object.CommitIter], and additionally returns a pointer to error.
// The pointer to error is guaranteed to be populated with either nil or the
// error returned by the commit iterator after the returned iterator is
// finished.
func commitIterSeqErr(commitIter object.CommitIter) (iter.Seq[*object.Commit], *error) {
	var err error
	return func(yield func(*object.Commit) bool) {
		for {
			commit, err2 := commitIter.Next()
			if err2 != nil {
				if errors.Is(err2, io.EOF) {
					return
				}
				err = err2
				return
			}
			if !yield(commit) {
				return
			}
		}
	}, &err

}

// getRecentCommits fetches numCommits commits, starting from the headHash in a
// repo.
func getRecentCommits(repo *git.Repository, headHash plumbing.Hash, numCommits int) (recentCommits []*object.Commit, err error) {
	var commitIter object.CommitIter
	var thisCommit *object.Commit

	commitIter, err = repo.Log(&git.LogOptions{From: headHash}) //exhaustruct:ignore
	if err != nil {
		return nil, err
	}
	recentCommits = make([]*object.Commit, 0)
	defer commitIter.Close()
	if numCommits < 0 {
		for {
			thisCommit, err = commitIter.Next()
			if errors.Is(err, io.EOF) {
				return recentCommits, nil
			} else if err != nil {
				return nil, err
			}
			recentCommits = append(recentCommits, thisCommit)
		}
	} else {
		for range numCommits {
			thisCommit, err = commitIter.Next()
			if errors.Is(err, io.EOF) {
				return recentCommits, nil
			} else if err != nil {
				return nil, err
			}
			recentCommits = append(recentCommits, thisCommit)
		}
	}
	return recentCommits, err
}

// getRecentCommitsDisplay generates a slice of [commitDisplay] friendly for
// use in HTML templates, consisting of numCommits commits from headhash in the
// repo.
func getRecentCommitsDisplay(repo *git.Repository, headHash plumbing.Hash, numCommits int) (recentCommits []commitDisplayOld, err error) {
	var commitIter object.CommitIter
	var thisCommit *object.Commit

	commitIter, err = repo.Log(&git.LogOptions{From: headHash}) //exhaustruct:ignore
	if err != nil {
		return nil, err
	}
	recentCommits = make([]commitDisplayOld, 0)
	defer commitIter.Close()
	if numCommits < 0 {
		for {
			thisCommit, err = commitIter.Next()
			if errors.Is(err, io.EOF) {
				return recentCommits, nil
			} else if err != nil {
				return nil, err
			}
			recentCommits = append(recentCommits, commitDisplayOld{
				thisCommit.Hash,
				thisCommit.Author,
				thisCommit.Committer,
				thisCommit.Message,
				thisCommit.TreeHash,
			})
		}
	} else {
		for range numCommits {
			thisCommit, err = commitIter.Next()
			if errors.Is(err, io.EOF) {
				return recentCommits, nil
			} else if err != nil {
				return nil, err
			}
			recentCommits = append(recentCommits, commitDisplayOld{
				thisCommit.Hash,
				thisCommit.Author,
				thisCommit.Committer,
				thisCommit.Message,
				thisCommit.TreeHash,
			})
		}
	}
	return recentCommits, err
}

type commitDisplayOld struct {
	Hash      plumbing.Hash
	Author    object.Signature
	Committer object.Signature
	Message   string
	TreeHash  plumbing.Hash

}

// commitToPatch creates an [object.Patch] from the first parent of a given
// [object.Commit].
//
// TODO: This function should be deprecated as it only diffs with the first
// parent and does not correctly handle merge commits.
func commitToPatch(commit *object.Commit) (parentCommitHash plumbing.Hash, patch *object.Patch, err error) {
	var parentCommit *object.Commit
	var commitTree *object.Tree

	parentCommit, err = commit.Parent(0)
	switch {
	case errors.Is(err, object.ErrParentNotFound):
		if commitTree, err = commit.Tree(); err != nil {
			return
		}
		if patch, err = nullTree.Patch(commitTree); err != nil {
			return
		}
	case err != nil:
		return
	default:
		parentCommitHash = parentCommit.Hash
		if patch, err = parentCommit.Patch(commit); err != nil {
			return
		}
	}
	return
}

var nullTree object.Tree //nolint:gochecknoglobals

// SPDX-License-Identifier: AGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>

package forge

import (
	"net/http"

	"go.lindenii.runxiyu.org/forge/internal/git2c"
	"go.lindenii.runxiyu.org/forge/internal/render"
	"go.lindenii.runxiyu.org/forge/internal/web"
)

type commitDisplay struct {
	Hash    string
	Author  string
	Email   string
	Date    string
	Message string
}

// httpHandleRepoIndex provides the front page of a repo using git2d.
func (s *Server) httpHandleRepoIndex(w http.ResponseWriter, req *http.Request, params map[string]any) {
	repoName := params["repo_name"].(string)
	groupPath := params["group_path"].([]string)

	_, repoPath, _, _, _, _, _ := s.getRepoInfo(req.Context(), groupPath, repoName, "") // TODO: Don't use getRepoInfo

	client, err := git2c.NewClient(s.config.Git.Socket)
	if err != nil {
		web.ErrorPage500(templates, w, params, err.Error())
		return
	}
	defer client.Close()

	commits, readme, err := client.Cmd1(repoPath)
	if err != nil {
		web.ErrorPage500(templates, w, params, err.Error())
		return
	}

	params["commits"] = commits
	params["readme_filename"] = readme.Filename
	_, params["readme"] = render.Readme(readme.Content, readme.Filename)

	renderTemplate(w, "repo_index", params)

	// TODO: Caching
}