package common

/*
 * This file is part of Autogits.
 *
 * Copyright © 2024 SUSE LLC
 *
 * Autogits is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 2 of the License, or (at your option) any later
 * version.
 *
 * Autogits is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * Foobar. If not, see <https://www.gnu.org/licenses/>.
 */

import (
	"fmt"
	"io"
	"log"
	"net/url"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
)

//go:generate mockgen -source=git_utils.go -destination=mock/git_utils.go -typed

type GitSubmoduleLister interface {
	GitSubmoduleList(gitPath, commitId string) (submoduleList map[string]string, err error)
	GitSubmoduleCommitId(cwd, packageName, commitId string) (subCommitId string, valid bool)
}

type Git interface {
	GetPath() string

	CloneDevel(gitDir, outName, urlString string) error
	GitBranchHead(gitDir, branchName string) (string, error)
	io.Closer

	GitSubmoduleLister

	GitExecWithOutputOrPanic(cwd string, params ...string) string
	GitExecOrPanic(cwd string, params ...string)
	GitExec(cwd string, params ...string) error
	GitExecWithOutput(cwd string, params ...string) (string, error)
}

type GitHandlerImpl struct {
	DebugLogger bool

	GitPath     string
	GitCommiter string
	GitEmail    string
}

func (s *GitHandlerImpl) GetPath() string {
	return s.GitPath
}

type GitHandlerGenerator interface {
	CreateGitHandler(git_author, email, prjName string) (Git, error)
	ReadExistingPath(git_author, email, gitPath string) (Git, error)
}

type GitHandlerGeneratorImpl struct{}

func (s *GitHandlerGeneratorImpl) CreateGitHandler(git_author, email, prj_name string) (Git, error) {
	gitPath, err := os.MkdirTemp("", prj_name)
	if err != nil {
		return nil, fmt.Errorf("Cannot create temp dir: %w", err)
	}

	if err = os.Chmod(gitPath, 0700); err != nil {
		return nil, fmt.Errorf("Cannot fix permissions of temp dir: %w", err)
	}

	return s.ReadExistingPath(git_author, email, gitPath)
}

func (*GitHandlerGeneratorImpl) ReadExistingPath(git_author, email, gitPath string) (Git, error) {
	git := &GitHandlerImpl{
		GitCommiter: git_author,
		GitPath:     gitPath,
	}

	return git, nil
}

//func (h *GitHandler) ProcessBranchList() []string {
//	if h.HasError() {
//		return make([]string, 0)
//	}
//
//	trackedBranches, err := os.ReadFile(path.Join(h.GitPath, DefaultGitPrj, TrackedBranchesFile))
//	if err != nil {
//		if errors.Is(err, os.ErrNotExist) {
//			trackedBranches = []byte("factory")
//		} else {
//			h.LogError("file error reading '%s' file in repo", TrackedBranchesFile)
//			h.Error = err
//			return make([]string, 0)
//		}
//	}
//
//	return strings.Split(string(trackedBranches), "\n")
//}

type GitReference struct {
	Branch string
	Id     string
}

type GitReferences struct {
	refs []GitReference
}

func (refs *GitReferences) addReference(id, branch string) {
	for _, ref := range refs.refs {
		if ref.Id == id && ref.Branch == branch {
			return
		}
	}

	refs.refs = append(refs.refs, GitReference{Branch: branch, Id: id})
}

func (e *GitHandlerImpl) CloneDevel(gitDir, outName, urlString string) error {
	url, err := url.Parse(urlString)
	branch := url.Fragment
	url.Fragment = ""

	params := []string{"clone", "-o", "devel"}
	if len(branch) > 0 {
		params = append(params, "-b", branch)
	}
	params = append(params, url.String(), outName)

	if err != nil {
		return fmt.Errorf("error parsing SSH URL. %w", err)
	}
	out, err := e.GitExecWithOutput(gitDir, params...)
	if err != nil {
		return fmt.Errorf("error cloning %s.\n%s\nerr: %w", urlString, out, err)
	}
	return nil
}

func (e *GitHandlerImpl) GitBranchHead(gitDir, branchName string) (string, error) {
	id, err := e.GitExecWithOutput(gitDir, "rev-list", "-1", branchName)
	if err != nil {
		return "", fmt.Errorf("Can't find default remote branch: %s", branchName)
	}

	return strings.TrimSpace(id), nil
}

func (e *GitHandlerImpl) Close() error {
	if err := os.RemoveAll(e.GitPath); err != nil {
		return err
	}
	e.GitPath = ""
	return nil
}

type writeFunc func(data []byte) (int, error)

func (f writeFunc) Write(data []byte) (int, error) {
	return f(data)
}

func (h writeFunc) UnmarshalText(text []byte) error {
	_, err := h.Write(text)
	return err
}

func (h writeFunc) Close() error {
	_, err := h.Write(nil)
	return err
}

func (e *GitHandlerImpl) GitExecWithOutputOrPanic(cwd string, params ...string) string {
	out, err := e.GitExecWithOutput(cwd, params...)
	if err != nil {
		log.Panicln("git command failed:", params, "@", cwd, "err:", err)
	}
	return out
}

func (e *GitHandlerImpl) GitExecOrPanic(cwd string, params ...string) {
	if err := e.GitExec(cwd, params...); err != nil {
		log.Panicln("git command failed:", params, "@", cwd, "err:", err)
	}
}

func (e *GitHandlerImpl) GitExec(cwd string, params ...string) error {
	_, err := e.GitExecWithOutput(cwd, params...)
	return err
}

var ExtraGitParams []string

func (e *GitHandlerImpl) GitExecWithOutput(cwd string, params ...string) (string, error) {
	cmd := exec.Command("/usr/bin/git", params...)
	cmd.Env = []string{
		"GIT_CEILING_DIRECTORIES=" + e.GitPath,
		"GIT_CONFIG_GLOBAL=/dev/null",
		"GIT_AUTHOR_NAME=" + e.GitCommiter,
		"GIT_COMMITTER_NAME=" + e.GitCommiter,
		"EMAIL=not@exist@src.opensuse.org",
		"GIT_LFS_SKIP_SMUDGE=1",
		"GIT_SSH_COMMAND=/usr/bin/ssh -o StrictHostKeyChecking=yes",
	}
	if len(ExtraGitParams) > 0 {
		cmd.Env = append(cmd.Env, ExtraGitParams...)
	}
	cmd.Dir = filepath.Join(e.GitPath, cwd)
	cmd.Stdin = nil

	if e.DebugLogger {
		log.Printf("git execute: %#v\n", cmd.Args)
	}
	out, err := cmd.CombinedOutput()
	if e.DebugLogger {
		log.Println(string(out))
	}
	if err != nil {
		if e.DebugLogger {
			log.Printf(" *** error: %v\n", err)
		}
		return "", fmt.Errorf("error executing: git %#v \n%s\n err: %w", cmd.Args, out, err)
	}

	return string(out), nil
}

type ChanIO struct {
	ch chan byte
}

func (c *ChanIO) Write(p []byte) (int, error) {
	for _, b := range p {
		c.ch <- b
	}
	return len(p), nil
}

// read at least 1 byte, but don't block if nothing more in channel
func (c *ChanIO) Read(data []byte) (idx int, err error) {
	var ok bool

	data[idx], ok = <-c.ch
	if !ok {
		err = io.EOF
		return
	}
	idx++

	for len(c.ch) > 0 && idx < len(data) {
		data[idx], ok = <-c.ch
		if !ok {
			err = io.EOF
			return
		}

		idx++
	}

	return
}

type gitMsg struct {
	hash     string
	itemType string
	size     int
}

type commit struct {
	Tree string
	Msg  string
}

type tree_entry struct {
	name string
	mode int
	hash string

	size int
}

type tree struct {
	items []tree_entry
}

func (t *tree_entry) isSubmodule() bool {
	return (t.mode & 0170000) == 0160000
}

func (t *tree_entry) isTree() bool {
	return (t.mode & 0170000) == 0040000
}

func (t *tree_entry) isBlob() bool {
	return !t.isTree() && !t.isSubmodule()
}

func parseGitMsg(data <-chan byte) (gitMsg, error) {
	var id []byte = make([]byte, 64)
	var msgType []byte = make([]byte, 16)
	var size int

	pos := 0
	for c := <-data; c != ' '; c = <-data {
		if (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') {
			id[pos] = c
			pos++
		} else {
			return gitMsg{}, fmt.Errorf("Invalid character during object hash parse '%c' at %d", c, pos)
		}
	}
	id = id[:pos]

	pos = 0
	var c byte
	for c = <-data; c != ' ' && c != '\x00'; c = <-data {
		if c >= 'a' && c <= 'z' {
			msgType[pos] = c
			pos++
		} else {
			return gitMsg{}, fmt.Errorf("Invalid character during object type parse '%c' at %d", c, pos)
		}
	}
	msgType = msgType[:pos]

	switch string(msgType) {
	case "commit", "tree", "blob":
		break
	case "missing":
		if c != '\x00' {
			return gitMsg{}, fmt.Errorf("Missing format weird")
		}
		return gitMsg{
			hash:     string(id[:]),
			itemType: "missing",
			size:     0,
		}, fmt.Errorf("Object not found: '%s'", string(id))
	default:
		return gitMsg{}, fmt.Errorf("Invalid object type: '%s'", string(msgType))
	}

	for c = <-data; c != '\000'; c = <-data {
		if c >= '0' && c <= '9' {
			size = size*10 + (int(c) - '0')
		} else {
			return gitMsg{}, fmt.Errorf("Invalid character during object size parse: '%c'", c)
		}
	}

	return gitMsg{
		hash:     string(id[:]),
		itemType: string(msgType),
		size:     size,
	}, nil
}

func parseGitCommitHdr(data <-chan byte) ([2]string, error) {
	hdr := make([]byte, 0, 60)
	val := make([]byte, 0, 1000)

	c := <-data
	if c != '\n' { // end of header marker
		for ; c != ' '; c = <-data {
			hdr = append(hdr, c)
		}
		for c := <-data; c != '\n'; c = <-data {
			val = append(val, c)
		}
	}

	return [2]string{string(hdr), string(val)}, nil
}

func parseGitCommitMsg(data <-chan byte, l int) (string, error) {
	msg := make([]byte, 0, l)

	for c := <-data; c != '\x00'; c = <-data {
		msg = append(msg, c)
		l--
	}
	//	l--

	if l != 0 {
		return "", fmt.Errorf("Unexpected data in the git commit msg: l=%d", l)
	}

	return string(msg), nil
}

func parseGitCommit(data <-chan byte) (commit, error) {
	hdr, err := parseGitMsg(data)
	if err != nil {
		return commit{}, err
	} else if hdr.itemType != "commit" {
		return commit{}, fmt.Errorf("expected commit but parsed %s", hdr.itemType)
	}

	var c commit
	l := hdr.size
	for {
		hdr, err := parseGitCommitHdr(data)
		if err != nil {
			return commit{}, nil
		}

		if len(hdr[0])+len(hdr[1]) == 0 { // hdr end marker
			break
		}

		switch hdr[0] {
		case "tree":
			c.Tree = hdr[1]
		}

		l -= len(hdr[0]) + len(hdr[1]) + 2
	}
	l--

	c.Msg, err = parseGitCommitMsg(data, l)
	return c, err
}

func parseTreeEntry(data <-chan byte, hashLen int) (tree_entry, error) {
	var e tree_entry

	for c := <-data; c != ' '; c = <-data {
		e.mode = e.mode*8 + int(c-'0')
		e.size++
	}
	e.size++

	name := make([]byte, 0, 128)
	for c := <-data; c != '\x00'; c = <-data {
		name = append(name, c)
		e.size++
	}
	e.size++
	e.name = string(name)

	const hexBinToAscii = "0123456789abcdef"

	hash := make([]byte, 0, hashLen*2)
	for range hashLen {
		c := <-data
		hash = append(hash, hexBinToAscii[((c&0xF0)>>4)], hexBinToAscii[c&0xF])
	}
	e.hash = string(hash)
	e.size += hashLen

	return e, nil
}

func parseGitTree(data <-chan byte) (tree, error) {

	hdr, err := parseGitMsg(data)
	if err != nil {
		return tree{}, err
	}

	// max capacity to length of hash
	t := tree{items: make([]tree_entry, 0, hdr.size/len(hdr.hash))}
	parsedLen := 0
	for parsedLen < hdr.size {
		entry, err := parseTreeEntry(data, len(hdr.hash)/2)
		if err != nil {
			return tree{}, nil
		}

		t.items = append(t.items, entry)
		parsedLen += entry.size
	}
	c := <-data // \0 read

	if c != '\x00' {
		return t, fmt.Errorf("Unexpected character during git tree data read")
	}

	if parsedLen != hdr.size {
		return t, fmt.Errorf("Invalid size of git tree data")
	}

	return t, nil
}

func parseGitBlob(data <-chan byte) ([]byte, error) {
	hdr, err := parseGitMsg(data)
	if err != nil {
		return []byte{}, err
	}

	d := make([]byte, hdr.size)
	for l := 0; l < hdr.size; l++ {
		d[l] = <-data
	}
	eob := <-data
	if eob != '\x00' {
		return d, fmt.Errorf("invalid byte read in parseGitBlob")
	}

	return d, nil
}

func (e *GitHandlerImpl) GitParseCommits(cwd string, commitIDs []string) (parsedCommits []commit, err error) {
	var done sync.Mutex

	done.Lock()
	data_in, data_out := ChanIO{make(chan byte, 256)}, ChanIO{make(chan byte, 70)}
	parsedCommits = make([]commit, 0, len(commitIDs))

	go func() {
		defer done.Unlock()
		defer close(data_out.ch)

		for _, id := range commitIDs {
			data_out.Write([]byte(id))
			data_out.ch <- '\x00'
			c, e := parseGitCommit(data_in.ch)
			if e != nil {
				err = fmt.Errorf("Error parsing git commit: %w", e)
				return
			}

			parsedCommits = append(parsedCommits, c)
		}
	}()

	cmd := exec.Command("/usr/bin/git", "cat-file", "--batch", "-Z")
	cmd.Env = []string{
		"GIT_CEILING_DIRECTORIES=" + e.GitPath,
		"GIT_CONFIG_GLOBAL=/dev/null",
	}
	cmd.Dir = filepath.Join(e.GitPath, cwd)
	cmd.Stdout = &data_in
	cmd.Stdin = &data_out
	cmd.Stderr = writeFunc(func(data []byte) (int, error) {
		if e.DebugLogger {
			log.Printf(string(data))
		}
		return len(data), nil
	})
	if e.DebugLogger {
		log.Printf("command run: %v\n", cmd.Args)
	}
	err = cmd.Run()

	done.Lock()
	return
}

// TODO: support sub-trees
func (e *GitHandlerImpl) GitCatFile(cwd, commitId, filename string) (data []byte, err error) {
	var done sync.Mutex

	done.Lock()
	data_in, data_out := ChanIO{make(chan byte, 256)}, ChanIO{make(chan byte, 70)}

	go func() {
		defer done.Unlock()
		defer close(data_out.ch)

		data_out.Write([]byte(commitId))
		data_out.ch <- '\x00'
		c, err := parseGitCommit(data_in.ch)
		if err != nil {
			log.Printf("Error parsing git commit: %v\n", err)
			return
		}
		data_out.Write([]byte(c.Tree))
		data_out.ch <- '\x00'
		tree, err := parseGitTree(data_in.ch)

		if err != nil {
			if e.DebugLogger {
				log.Printf("Error parsing git tree: %v\n", err)
			}
			return
		}

		for _, te := range tree.items {
			if te.isBlob() && te.name == filename {
				data_out.Write([]byte(te.hash))
				data_out.ch <- '\x00'
				data, err = parseGitBlob(data_in.ch)
				return
			}
		}

		err = fmt.Errorf("file not found: '%s'", filename)
	}()

	cmd := exec.Command("/usr/bin/git", "cat-file", "--batch", "-Z")
	cmd.Env = []string{
		"GIT_CEILING_DIRECTORIES=" + e.GitPath,
		"GIT_CONFIG_GLOBAL=/dev/null",
	}
	cmd.Dir = filepath.Join(e.GitPath, cwd)
	cmd.Stdout = &data_in
	cmd.Stdin = &data_out
	cmd.Stderr = writeFunc(func(data []byte) (int, error) {
		if e.DebugLogger {
			log.Printf(string(data))
		}
		return len(data), nil
	})
	if e.DebugLogger {
		log.Printf("command run: %v\n", cmd.Args)
	}
	err = cmd.Run()

	done.Lock()
	return
}

// return (filename) -> (hash) map for all submodules
// TODO: recursive? map different orgs, not just assume '.' for path
func (e *GitHandlerImpl) GitSubmoduleList(gitPath, commitId string) (submoduleList map[string]string, err error) {
	var done sync.Mutex
	submoduleList = make(map[string]string)

	done.Lock()
	data_in, data_out := ChanIO{make(chan byte, 256)}, ChanIO{make(chan byte, 70)}

	go func() {
		defer done.Unlock()
		defer close(data_out.ch)

		data_out.Write([]byte(commitId))
		data_out.ch <- '\x00'
		var c commit
		c, err = parseGitCommit(data_in.ch)
		if err != nil {
			err = fmt.Errorf("Error parsing git commit. Err: %w", err)
			return
		}
		data_out.Write([]byte(c.Tree))
		data_out.ch <- '\x00'
		var tree tree
		tree, err = parseGitTree(data_in.ch)

		if err != nil {
			err = fmt.Errorf("Error parsing git tree: %w", err)
			return
		}

		for _, te := range tree.items {
			if te.isSubmodule() {
				submoduleList[te.name] = te.hash
			}
		}
	}()

	cmd := exec.Command("/usr/bin/git", "cat-file", "--batch", "-Z")
	cmd.Env = []string{
		"GIT_CEILING_DIRECTORIES=" + e.GitPath,
		"GIT_CONFIG_GLOBAL=/dev/null",
	}
	cmd.Dir = filepath.Join(e.GitPath, gitPath)
	cmd.Stdout = &data_in
	cmd.Stdin = &data_out
	cmd.Stderr = writeFunc(func(data []byte) (int, error) {
		if e.DebugLogger {
			log.Println(string(data))
		}
		return len(data), nil
	})
	if e.DebugLogger {
		log.Printf("command run: %v\n", cmd.Args)
	}
	err = cmd.Run()

	done.Lock()
	return submoduleList, err
}

func (e *GitHandlerImpl) GitSubmoduleCommitId(cwd, packageName, commitId string) (subCommitId string, valid bool) {
	defer func() {
		if recover() != nil {
			commitId = ""
			valid = false
		}
	}()

	data_in, data_out := ChanIO{make(chan byte, 256)}, ChanIO{make(chan byte, 70)}
	var wg sync.WaitGroup

	wg.Add(1)

	if e.DebugLogger {
		log.Printf("getting commit id '%s' from git at '%s' with packageName: %s\n", commitId, cwd, packageName)
	}

	go func() {
		defer wg.Done()
		defer close(data_out.ch)

		data_out.Write([]byte(commitId))
		data_out.ch <- '\x00'
		c, err := parseGitCommit(data_in.ch)
		if err != nil {
			log.Panicf("Error parsing git commit: %v\n", err)
		}
		data_out.Write([]byte(c.Tree))
		data_out.ch <- '\x00'
		tree, err := parseGitTree(data_in.ch)

		if err != nil {
			log.Panicf("Error parsing git tree: %v\n", err)
		}

		for _, te := range tree.items {
			if te.name == packageName && te.isSubmodule() {
				subCommitId = te.hash
				return
			}
		}
	}()

	cmd := exec.Command("/usr/bin/git", "cat-file", "--batch", "-Z")
	cmd.Env = []string{
		"GIT_CEILING_DIRECTORIES=" + e.GitPath,
		"GIT_CONFIG_GLOBAL=/dev/null",
	}
	cmd.Dir = filepath.Join(e.GitPath, cwd)
	cmd.Stdout = &data_in
	cmd.Stdin = &data_out
	cmd.Stderr = writeFunc(func(data []byte) (int, error) {
		log.Println(string(data))
		return len(data), nil
	})
	if e.DebugLogger {
		log.Printf("command run: %v\n", cmd.Args)
	}
	if err := cmd.Run(); err != nil {
		log.Printf("Error running command %v, err: %v", cmd.Args, err)
	}

	wg.Wait()
	return subCommitId, len(subCommitId) == len(commitId)
}