// mgsh (git shell) — Go port of the original Perl mgsh (mwx'2026).
//
// A small interactive shell / command-line wrapper around a self-hosted bare
// git server, reachable over ssh. It manages a flat set of projects living
// under a base directory (default $HOME/src, or /db/src on Linux).
//
// Configuration lives in ~/.mgshrc and/or MGSH_* environment variables; see
// config.go and the README.
package main

import (
	"fmt"
	"io"
	"os"
	"os/user"
	"path/filepath"
	"strings"

	"github.com/chzyer/readline"
)

// VERSION is a var (not const) so the build script can inject the current build
// number via -ldflags "-X main.VERSION=...". The default is used for a plain
// `go build`.
var VERSION = "4.0.0"

const INFO = "mwx'2026"

// Global runtime state.
var (
	cfg      Config // resolved configuration
	BASE     string // project base directory (cfg.Base)
	URL      string // ssh:// clone/push URL
	PRJ      string // current project (may be empty)
	DIR      string // current working directory (BASE or BASE/PRJ)
	IP       string // local IP, embedded into the initial commit message
	HOST     string // short hostname
	USER     string // current user name
	REPO     string // repository name parsed from remote.origin.url
	BPLSTATE string // "/OFF" if build.pl symlink points at a *.off file
	BRANCH   string // current git branch of the active project (if any)
	DIRTY    bool   // whether the active project has uncommitted changes
	useColor bool   // whether to render ANSI colors
)

func main() {
	setup()
	useColor = readline.IsTerminal(int(os.Stdout.Fd()))

	fmt.Println(banner())

	// preset project from the first argument (interactive launch: `mgsh myproj`)
	if len(os.Args) > 1 && isDir(BASE+"/"+os.Args[1]) {
		PRJ = os.Args[1]
	}

	// command-line mode: `mgsh <command> [args...]`
	clCmd, cmdline, isHelp := parseArgs()
	if isHelp {
		help()
		return
	}
	if clCmd != 0 {
		pwd, _ := os.Getwd()
		PRJ = ""
		if strings.HasPrefix(pwd, BASE+"/") {
			PRJ = pwd[len(BASE)+1:]
		}
		if clCmd == 2 {
			cmdline = strings.TrimSpace(cmdline + " " + PRJ)
		}
		updateDirState()
		runCommand(cmdline)
		return
	}

	runInteractive()
}

// runInteractive drives the colored, history- and completion-enabled REPL.
func runInteractive() {
	home, _ := os.UserHomeDir()

	rl, err := readline.NewEx(&readline.Config{
		Prompt:            promptString(),
		HistoryFile:       filepath.Join(home, ".mgsh_history"),
		AutoComplete:      completer(),
		InterruptPrompt:   "^C",
		EOFPrompt:         "quit",
		HistorySearchFold: true,
	})
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	defer rl.Close()

	for {
		updateDirState()
		rl.SetPrompt(promptString())
		line, err := rl.Readline()
		if err == readline.ErrInterrupt { // Ctrl-C: clear a typed line, else quit
			if len(line) == 0 {
				break
			}
			continue
		} else if err == io.EOF { // Ctrl-D
			break
		}
		if !runCommand(strings.TrimSpace(line)) {
			break
		}
	}
}

// parseArgs mirrors the original command-line dispatch table. It returns the
// "CLCMD" class (0 = interactive, 1 = plain, 2 = append project name), the raw
// command line, and whether `help` was requested.
func parseArgs() (int, string, bool) {
	if len(os.Args) < 2 {
		return 0, "", false
	}
	a0 := os.Args[1]
	if a0 == "help" {
		return 0, "", true
	}
	cls := map[string]int{
		"clone": 2, "init": 2, "log": 2,
		"push": 1, "pushremote": 1, "list": 1, "tag": 1, "archive": 1, "show": 1, "open": 1,
		"pull": 1, "fetch": 1, "status": 1, "diff": 1, "overview": 1,
	}
	if c, ok := cls[a0]; ok {
		return c, strings.Join(os.Args[1:], " "), false
	}
	return 0, "", false
}

func setup() {
	cfg = loadConfig()
	if miss := cfg.missingRequired(); len(miss) > 0 {
		fmt.Fprintf(os.Stderr, "mgsh: not configured — missing required settings: %s\n", strings.Join(miss, ", "))
		fmt.Fprintf(os.Stderr, "edit %s or set the corresponding MGSH_* environment variables, then run mgsh again.\n", configFile())
		os.Exit(1)
	}
	BASE = cfg.Base
	if !isDir(BASE) {
		fmt.Fprintf(os.Stderr, "%s not found\n", BASE)
		os.Exit(1)
	}

	URL = fmt.Sprintf("ssh://%s@%s:%s%s", cfg.GitUser, cfg.GitHost, cfg.GitPort, cfg.GitPath)
	IP = resolveIP()
	HOST = shortHostname()
	if u, err := user.Current(); err == nil {
		USER = u.Username
	}

	// git identity / settings, from config (defaults preserve prior behavior)
	if cfg.GitName != "" {
		git("", "config", "--global", "user.name", cfg.GitName)
	}
	if cfg.GitEmail != "" {
		git("", "config", "--global", "user.email", cfg.GitEmail)
	}
	if cfg.PushDefault != "" {
		git("", "config", "--global", "push.default", cfg.PushDefault)
	}

	loadAliases()
}

// updateDirState recomputes DIR, the build.pl OFF marker, the current branch /
// dirty flag and the parsed repository name for the active project. Run once
// per loop iteration.
func updateDirState() {
	BRANCH = ""
	DIRTY = false

	if PRJ != "" && isDir(BASE+"/"+PRJ) {
		DIR = BASE + "/" + PRJ
		BPLSTATE = ""
		bp := DIR + "/build.pl"
		if fi, err := os.Lstat(bp); err == nil && fi.Mode()&os.ModeSymlink != 0 {
			if target, err := os.Readlink(bp); err == nil && strings.HasSuffix(target, ".off") {
				BPLSTATE = "/OFF"
			}
		}
		if isDir(DIR + "/.git") {
			if out, err := gitCapture(DIR, "rev-parse", "--abbrev-ref", "HEAD"); err == nil {
				BRANCH = strings.TrimSpace(out)
			}
			if out, err := gitCapture(DIR, "status", "--porcelain"); err == nil && strings.TrimSpace(out) != "" {
				DIRTY = true
			}
		}
	} else {
		DIR = BASE
		BPLSTATE = ""
	}

	// derive REPO from the origin URL: basename without the ".git" suffix.
	REPO = ""
	if out, err := gitCapture(DIR, "config", "remote.origin.url"); err == nil {
		remurl := strings.TrimRight(strings.TrimSpace(out), "/")
		if remurl != "" {
			REPO = strings.TrimSuffix(filepath.Base(remurl), ".git")
		}
	}
}