package agent

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
)

// runExtCommand dispatches `zot ext ...` subcommands. Returns
// (handled=true, err) if rawArgs starts with "ext"; otherwise
// (handled=false, nil) so the main router falls through to the
// regular flag parser.
func runExtCommand(rawArgs []string) (handled bool, err error) {
	if len(rawArgs) == 0 || rawArgs[0] != "ext" {
		return false, nil
	}
	if len(rawArgs) == 1 {
		printExtHelp()
		return true, nil
	}
	switch rawArgs[1] {
	case "list":
		return true, extList()
	case "logs":
		return true, extLogs(rawArgs[2:])
	case "enable":
		return true, extToggle(rawArgs[2:], true)
	case "disable":
		return true, extToggle(rawArgs[2:], false)
	case "remove", "rm":
		return true, extRemove(rawArgs[2:])
	case "install":
		return true, extInstall(rawArgs[2:])
	case "help", "-h", "--help":
		printExtHelp()
		return true, nil
	default:
		printExtHelp()
		return true, fmt.Errorf("unknown ext subcommand: %s", rawArgs[1])
	}
}

func printExtHelp() {
	fmt.Fprintln(os.Stderr, `zot ext — manage extensions

usage:
  zot ext list                    list installed extensions and their state
  zot ext logs <name> [-f]        cat / tail an extension's stderr log
  zot ext enable <name>           re-enable a disabled extension
  zot ext disable <name>          disable without removing
  zot ext remove <name>           delete an extension directory
  zot ext install <path|git-url>  copy / clone an extension into $ZOT_HOME/extensions/

extensions live under:
  $ZOT_HOME/extensions/<name>/extension.json   (global)
  ./.zot/extensions/<name>/extension.json      (project-local)`)
}

// extList walks both the global and project-local extension dirs and
// prints a one-row-per-extension table.
func extList() error {
	type row struct {
		Scope    string
		Name     string
		Version  string
		Enabled  string
		Language string
		Dir      string
	}
	var rows []row
	for scope, dir := range extensionDirs() {
		entries, err := os.ReadDir(dir)
		if err != nil {
			continue
		}
		for _, e := range entries {
			if !e.IsDir() {
				continue
			}
			extDir := filepath.Join(dir, e.Name())
			mfPath := filepath.Join(extDir, "extension.json")
			raw, err := os.ReadFile(mfPath)
			if err != nil {
				continue
			}
			var m struct {
				Name     string `json:"name"`
				Version  string `json:"version"`
				Language string `json:"language"`
				Enabled  *bool  `json:"enabled"`
			}
			if err := json.Unmarshal(raw, &m); err != nil {
				continue
			}
			enabled := "yes"
			if m.Enabled != nil && !*m.Enabled {
				enabled = "no"
			}
			rows = append(rows, row{
				Scope: scope, Name: m.Name, Version: m.Version,
				Enabled: enabled, Language: m.Language, Dir: extDir,
			})
		}
	}
	if len(rows) == 0 {
		fmt.Fprintln(os.Stderr, "no extensions installed")
		fmt.Fprintln(os.Stderr, "see docs/extensions.md to write your own, or `zot ext install <path|url>`")
		return nil
	}
	fmt.Printf("%-12s  %-20s  %-10s  %-8s  %-10s  %s\n", "scope", "name", "version", "enabled", "language", "dir")
	for _, r := range rows {
		fmt.Printf("%-12s  %-20s  %-10s  %-8s  %-10s  %s\n",
			r.Scope, r.Name, dashIfEmpty(r.Version),
			r.Enabled, dashIfEmpty(r.Language), r.Dir)
	}
	return nil
}

// extLogs locates the named extension's log file and either cats or
// tails it (-f).
func extLogs(args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: zot ext logs <name> [-f]")
	}
	name := args[0]
	follow := false
	for _, a := range args[1:] {
		if a == "-f" || a == "--follow" {
			follow = true
		}
	}
	logPath := filepath.Join(ZotHome(), "logs", "ext-"+name+".log")
	if _, err := os.Stat(logPath); err != nil {
		return fmt.Errorf("no log for %q at %s", name, logPath)
	}
	if !follow {
		f, err := os.Open(logPath)
		if err != nil {
			return err
		}
		defer f.Close()
		_, err = io.Copy(os.Stdout, f)
		return err
	}
	cmd := exec.Command("tail", "-F", logPath)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

// extToggle flips the enabled flag in an extension's manifest.
func extToggle(args []string, enabled bool) error {
	if len(args) == 0 {
		verb := "enable"
		if !enabled {
			verb = "disable"
		}
		return fmt.Errorf("usage: zot ext %s <name>", verb)
	}
	name := args[0]
	dir, err := findExtensionDir(name)
	if err != nil {
		return err
	}
	mfPath := filepath.Join(dir, "extension.json")
	raw, err := os.ReadFile(mfPath)
	if err != nil {
		return err
	}
	var generic map[string]any
	if err := json.Unmarshal(raw, &generic); err != nil {
		return fmt.Errorf("parse manifest: %w", err)
	}
	generic["enabled"] = enabled
	out, err := json.MarshalIndent(generic, "", "  ")
	if err != nil {
		return err
	}
	if err := os.WriteFile(mfPath, append(out, '\n'), 0o644); err != nil {
		return err
	}
	state := "enabled"
	if !enabled {
		state = "disabled"
	}
	fmt.Fprintf(os.Stderr, "%s %s\n", state, name)
	return nil
}

// extRemove deletes an extension's directory after a confirmation
// prompt (skip with --yes).
func extRemove(args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: zot ext remove <name> [--yes]")
	}
	name := args[0]
	yes := false
	for _, a := range args[1:] {
		if a == "--yes" || a == "-y" {
			yes = true
		}
	}
	dir, err := findExtensionDir(name)
	if err != nil {
		return err
	}
	if !yes {
		fmt.Fprintf(os.Stderr, "remove %s ? [y/N] ", dir)
		var resp string
		_, _ = fmt.Scanln(&resp)
		if !strings.EqualFold(strings.TrimSpace(resp), "y") {
			fmt.Fprintln(os.Stderr, "aborted")
			return nil
		}
	}
	if err := os.RemoveAll(dir); err != nil {
		return err
	}
	fmt.Fprintf(os.Stderr, "removed %s\n", dir)
	return nil
}

// extInstall copies a local directory or shallow-clones a git URL
// into $ZOT_HOME/extensions/. Validates the destination contains an
// extension.json before reporting success.
func extInstall(args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: zot ext install <path|git-url>")
	}
	src := args[0]
	dest := filepath.Join(ZotHome(), "extensions")
	if err := os.MkdirAll(dest, 0o755); err != nil {
		return err
	}

	if strings.HasPrefix(src, "https://") || strings.HasPrefix(src, "git@") || strings.HasSuffix(src, ".git") {
		// Git clone path. Pick the destination name from the repo basename.
		name := strings.TrimSuffix(filepath.Base(src), ".git")
		out := filepath.Join(dest, name)
		if _, err := os.Stat(out); err == nil {
			return fmt.Errorf("destination %s already exists; remove it first", out)
		}
		cmd := exec.Command("git", "clone", "--depth", "1", src, out)
		cmd.Stdout = os.Stderr
		cmd.Stderr = os.Stderr
		if err := cmd.Run(); err != nil {
			return fmt.Errorf("git clone: %w", err)
		}
		if _, err := os.Stat(filepath.Join(out, "extension.json")); err != nil {
			_ = os.RemoveAll(out)
			return fmt.Errorf("installed dir lacks extension.json; aborted and rolled back")
		}
		fmt.Fprintf(os.Stderr, "installed %s\n", out)
		return nil
	}

	// Local path: must be a directory containing extension.json.
	info, err := os.Stat(src)
	if err != nil {
		return err
	}
	if !info.IsDir() {
		return fmt.Errorf("not a directory: %s", src)
	}
	if _, err := os.Stat(filepath.Join(src, "extension.json")); err != nil {
		return fmt.Errorf("source lacks extension.json")
	}
	// Resolve to an absolute, cleaned path before deriving the install
	// name. Otherwise relative sources like "." or "./" collapse to a
	// basename of ".", and the destination wrongly resolves to the
	// extensions/ parent directory (which zot creates on first run),
	// triggering a false "already exists" failure.
	absSrc, err := filepath.Abs(src)
	if err != nil {
		return err
	}
	name := filepath.Base(absSrc)
	if name == "." || name == ".." || name == string(filepath.Separator) || name == "" {
		return fmt.Errorf("cannot derive extension name from %q", src)
	}
	out := filepath.Join(dest, name)
	if _, err := os.Stat(out); err == nil {
		return fmt.Errorf("destination %s already exists; remove it first", out)
	}
	if err := copyDir(absSrc, out); err != nil {
		return err
	}
	fmt.Fprintf(os.Stderr, "installed %s\n", out)
	return nil
}

func extensionDirs() map[string]string {
	out := map[string]string{}
	if h := ZotHome(); h != "" {
		out["global"] = filepath.Join(h, "extensions")
	}
	if cwd, err := os.Getwd(); err == nil {
		out["project"] = filepath.Join(cwd, ".zot", "extensions")
	}
	return out
}

func findExtensionDir(name string) (string, error) {
	for _, dir := range extensionDirs() {
		candidate := filepath.Join(dir, name)
		if _, err := os.Stat(filepath.Join(candidate, "extension.json")); err == nil {
			return candidate, nil
		}
	}
	return "", fmt.Errorf("extension %q not found", name)
}

func dashIfEmpty(s string) string {
	if s == "" {
		return "-"
	}
	return s
}

// copyDir does a recursive copy of src to dst preserving file mode
// bits. Used by `zot ext install <local-path>`.
//
// Entries matched by the source's root .gitignore are skipped, and
// .git itself is always skipped. This keeps non-portable, regeneratable
// directories (e.g. .venv with hardcoded rpaths, node_modules, target/)
// out of the installed copy so the extension stays functional at its new
// location.
func copyDir(src, dst string) error {
	ig := loadGitignore(src)
	return filepath.Walk(src, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		rel, err := filepath.Rel(src, path)
		if err != nil {
			return err
		}
		if rel != "." {
			name := filepath.Base(rel)
			if info.IsDir() && name == ".git" {
				return filepath.SkipDir
			}
			if ig.match(filepath.ToSlash(rel), info.IsDir()) {
				if info.IsDir() {
					return filepath.SkipDir
				}
				return nil
			}
		}
		target := filepath.Join(dst, rel)
		if info.IsDir() {
			return os.MkdirAll(target, info.Mode())
		}
		in, err := os.Open(path)
		if err != nil {
			return err
		}
		defer in.Close()
		out, err := os.OpenFile(target, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, info.Mode())
		if err != nil {
			return err
		}
		defer out.Close()
		_, err = io.Copy(out, in)
		return err
	})
}

// gitignore is a minimal .gitignore matcher. It supports the common
// patterns used in real extension repos: blank lines, comments (#),
// negation (!), directory-only patterns (trailing /), anchored
// patterns (leading /), and the * / ? / [..] wildcards via
// filepath.Match. It intentionally does not implement ** globstar or
// nested per-directory .gitignore files; the goal is to drop obvious
// non-portable directories, not to be a faithful git reimplementation.
type gitignore struct {
	rules []gitignoreRule
}

type gitignoreRule struct {
	pattern  string
	negate   bool
	dirOnly  bool
	anchored bool
}

func loadGitignore(root string) *gitignore {
	data, err := os.ReadFile(filepath.Join(root, ".gitignore"))
	if err != nil {
		return &gitignore{}
	}
	return loadGitignoreFromString(string(data))
}

func loadGitignoreFromString(data string) *gitignore {
	g := &gitignore{}
	for _, line := range strings.Split(data, "\n") {
		line = strings.TrimRight(line, "\r")
		trimmed := strings.TrimSpace(line)
		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
			continue
		}
		r := gitignoreRule{pattern: trimmed}
		if strings.HasPrefix(r.pattern, "!") {
			r.negate = true
			r.pattern = r.pattern[1:]
		}
		if strings.HasSuffix(r.pattern, "/") {
			r.dirOnly = true
			r.pattern = strings.TrimSuffix(r.pattern, "/")
		}
		if strings.HasPrefix(r.pattern, "/") {
			r.anchored = true
			r.pattern = strings.TrimPrefix(r.pattern, "/")
		}
		if r.pattern == "" {
			continue
		}
		g.rules = append(g.rules, r)
	}
	return g
}

// match reports whether the slash-separated relative path should be
// ignored. Later rules win, so a trailing negation can re-include a
// previously ignored path.
func (g *gitignore) match(rel string, isDir bool) bool {
	ignored := false
	for _, r := range g.rules {
		if r.dirOnly && !isDir {
			continue
		}
		if r.matchPath(rel) {
			ignored = !r.negate
		}
	}
	return ignored
}

func (r gitignoreRule) matchPath(rel string) bool {
	if r.anchored || strings.Contains(r.pattern, "/") {
		if ok, _ := filepath.Match(r.pattern, rel); ok {
			return true
		}
		// Anchored directory pattern also matches everything beneath it.
		return strings.HasPrefix(rel, r.pattern+"/")
	}
	// Unanchored: match the basename of any path component.
	base := rel
	if i := strings.LastIndex(rel, "/"); i >= 0 {
		base = rel[i+1:]
	}
	if ok, _ := filepath.Match(r.pattern, base); ok {
		return true
	}
	// Match a directory component anywhere in the path.
	for _, part := range strings.Split(rel, "/") {
		if ok, _ := filepath.Match(r.pattern, part); ok {
			return true
		}
	}
	return false
}