package bash

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

	"github.com/chzyer/readline"

	"github.com/cametendo/bash-for-windows/internal/shell"
)

func Run() error {
	args := os.Args[1:]

	if len(args) > 0 {
		switch args[0] {
		case "-c":
			if len(args) < 2 {
				return fmt.Errorf("-c: option requires an argument")
			}
			sh := shell.New()
			if len(args) > 2 {
				sh.SetArgs(args[2:])
			}
			return sh.Execute(strings.Join(args[1:], " "))
		case "--version":
			fmt.Println("bash-for-windows 2.0.0 (Go-based)")
			fmt.Println("Provides bash-compatible shell for Windows.")
			return nil
		default:
			return runFile(args[0], args[1:])
		}
	}

	return interactive()
}

func runFile(path string, args []string) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return fmt.Errorf("%s: %v", path, err)
	}
	sh := shell.New()
	sh.SetArgs(append([]string{path}, args...))
	sh.SetVar("0", path)
	return sh.Execute(string(data))
}

func historyFile() string {
	home, err := os.UserHomeDir()
	if err != nil {
		return ""
	}
	// On Windows this lands in %USERPROFILE%\.bash_history
	return filepath.Join(home, ".bash_history")
}

func interactive() error {
	sh := shell.New()

	// Build completer
	completer := readline.NewPrefixCompleter(
		readline.PcItemDynamic(func(line string) []string {
			return dynamicComplete(sh, line)
		}),
	)

	rl, err := readline.NewEx(&readline.Config{
		HistoryFile:            historyFile(),
		AutoComplete:           completer,
		InterruptPrompt:        "^C",
		EOFPrompt:              "exit",
		HistorySearchFold:      true,
		FuncFilterInputRune:    filterInput,
	})
	if err != nil {
		// Fall back to dumb interactive mode
		return interactiveDumb(sh)
	}
	defer rl.Close()

	fmt.Fprintln(os.Stdout, "bash-for-windows v2.0.0  (type 'exit' or Ctrl+D to quit)")

	var multiLine strings.Builder

	for {
		prompt := buildPrompt(sh)
		if multiLine.Len() > 0 {
			prompt = "> "
		}
		rl.SetPrompt(prompt)

		line, err := rl.Readline()
		if err != nil {
			if err.Error() == "Interrupt" {
				// Ctrl+C: abort current multi-line input
				multiLine.Reset()
				fmt.Fprintln(os.Stdout)
				continue
			}
			break // EOF
		}

		if multiLine.Len() > 0 {
			multiLine.WriteString("\n")
		}
		multiLine.WriteString(line)

		input := multiLine.String()
		if shell.IsIncomplete(input) {
			continue // wait for more input
		}
		multiLine.Reset()

		input = strings.TrimSpace(input)
		if input == "" {
			continue
		}

		if err := sh.Execute(input); err != nil {
			fmt.Fprintf(os.Stderr, "bash: %v\n", err)
		}
	}
	return nil
}

// interactiveDumb is a fallback that doesn't need readline.
func interactiveDumb(sh *shell.Shell) error {
	fmt.Fprintln(os.Stdout, "bash-for-windows v2.0.0")

	var multiLine strings.Builder
	buf := make([]byte, 4096)

	for {
		prompt := buildPrompt(sh)
		if multiLine.Len() > 0 {
			prompt = "> "
		}
		fmt.Fprint(os.Stdout, prompt)

		n, err := os.Stdin.Read(buf)
		if n > 0 {
			chunk := string(buf[:n])
			if multiLine.Len() > 0 {
				multiLine.WriteString("\n")
			}
			multiLine.WriteString(strings.TrimRight(chunk, "\r\n"))

			input := multiLine.String()
			if shell.IsIncomplete(input) {
				continue
			}
			multiLine.Reset()
			input = strings.TrimSpace(input)
			if input == "" {
				continue
			}
			if execErr := sh.Execute(input); execErr != nil {
				fmt.Fprintf(os.Stderr, "bash: %v\n", execErr)
			}
		}
		if err != nil {
			break
		}
	}
	return nil
}

func buildPrompt(sh *shell.Shell) string {
	pwd, _ := os.Getwd()
	home, _ := os.UserHomeDir()
	if home != "" && strings.HasPrefix(pwd, home) {
		pwd = "~" + pwd[len(home):]
	}
	// Show exit code in prompt if non-zero
	exitCode := sh.GetVar("?")
	suffix := "$ "
	if exitCode != "0" && exitCode != "" {
		suffix = "[" + exitCode + "]$ "
	}
	return pwd + suffix
}

// dynamicComplete provides tab completion for commands and paths.
func dynamicComplete(sh *shell.Shell, line string) []string {
	line = strings.TrimLeft(line, " \t")
	var completions []string

	// Check if we're completing the first word (command) or an argument (path)
	words := strings.Fields(line)
	completingCommand := len(words) == 0 || (len(words) == 1 && !strings.HasSuffix(line, " "))

	if completingCommand {
		prefix := ""
		if len(words) == 1 {
			prefix = words[0]
		}
		// Builtin/function names — access via the shell instance
		// (we can't iterate unexported fields, so use a public method)
		for _, name := range sh.BuiltinNames() {
			if strings.HasPrefix(name, prefix) {
				completions = append(completions, name)
			}
		}
		// PATH executables
		for _, dir := range filepath.SplitList(os.Getenv("PATH")) {
			entries, err := os.ReadDir(dir)
			if err != nil {
				continue
			}
			for _, e := range entries {
				name := e.Name()
				// Strip .exe on completion display
				name = strings.TrimSuffix(name, ".exe")
				if strings.HasPrefix(name, prefix) {
					completions = append(completions, name)
				}
			}
		}
	} else {
		// Path completion
		prefix := ""
		if len(words) > 0 {
			prefix = words[len(words)-1]
			if strings.HasSuffix(line, " ") {
				prefix = ""
			}
		}
		dir := filepath.Dir(prefix)
		base := filepath.Base(prefix)
		if prefix == "" || strings.HasSuffix(prefix, "/") || strings.HasSuffix(prefix, "\\") {
			dir = prefix
			base = ""
		}
		entries, err := os.ReadDir(dir)
		if err == nil {
			for _, e := range entries {
				name := e.Name()
				if strings.HasPrefix(name, base) {
					p := filepath.Join(dir, name)
					if e.IsDir() {
						p += "/"
					}
					completions = append(completions, p)
				}
			}
		}
	}

	return completions
}

func filterInput(r rune) (rune, bool) {
	// Block Ctrl+Z (26) — on Windows this would suspend; we handle it gracefully
	if r == 26 {
		return r, false
	}
	return r, true
}