package readline

import (
	"io"
	"os"
	"os/signal"
	"sync"
	"syscall"

	"github.com/ergochat/readline/internal/platform"
)

type Instance struct {
	terminal  *terminal
	operation *operation

	closeOnce sync.Once
	closeErr  error
}

type Config struct {
	// Prompt is the input prompt (ANSI escape sequences are supported on all platforms)
	Prompt string

	// HistoryFile is the path to the file where persistent history will be stored
	// (empty string disables).
	HistoryFile string
	// HistoryLimit is the maximum number of history entries to store. If it is 0
	// or unset, the default value is 500; set to -1 to disable.
	HistoryLimit           int
	DisableAutoSaveHistory bool
	// HistorySearchFold enables case-insensitive history searching.
	HistorySearchFold bool

	// AutoComplete defines the tab-completion behavior. See the documentation for
	// the AutoCompleter interface for details.
	AutoComplete AutoCompleter

	// Listener is an optional callback to intercept keypresses.
	Listener Listener

	// Painter is an optional callback to rewrite the buffer for display.
	Painter Painter

	// FuncFilterInputRune is an optional callback to translate keyboard inputs;
	// it takes in the input rune and returns (translation, ok). If ok is false,
	// the rune is skipped.
	FuncFilterInputRune func(rune) (rune, bool)

	// VimMode enables Vim-style insert mode by default.
	VimMode bool

	InterruptPrompt string
	EOFPrompt       string

	EnableMask bool
	MaskRune   rune

	// Undo controls whether to maintain an undo buffer (if enabled,
	// Ctrl+_ will undo the previous action).
	Undo bool

	// These fields allow customizing terminal handling. Most clients should ignore them.
	Stdin              io.Reader
	Stdout             io.Writer
	Stderr             io.Writer
	FuncIsTerminal     func() bool
	FuncMakeRaw        func() error
	FuncExitRaw        func() error
	FuncGetSize        func() (width int, height int)
	FuncOnWidthChanged func(func())

	// private fields
	inited        bool
	isInteractive bool
}

func (c *Config) init() error {
	if c.inited {
		return nil
	}
	c.inited = true
	if c.Stdin == nil {
		c.Stdin = os.Stdin
	}

	if c.Stdout == nil {
		c.Stdout = os.Stdout
	}
	if c.Stderr == nil {
		c.Stderr = os.Stderr
	}
	if c.HistoryLimit == 0 {
		c.HistoryLimit = 500
	}

	if c.InterruptPrompt == "" {
		c.InterruptPrompt = "^C"
	} else if c.InterruptPrompt == "\n" {
		c.InterruptPrompt = ""
	}
	if c.EOFPrompt == "" {
		c.EOFPrompt = "^D"
	} else if c.EOFPrompt == "\n" {
		c.EOFPrompt = ""
	}

	if c.FuncGetSize == nil {
		c.FuncGetSize = platform.GetScreenSize
	}
	if c.FuncIsTerminal == nil {
		c.FuncIsTerminal = platform.DefaultIsTerminal
	}
	rm := new(rawModeHandler)
	if c.FuncMakeRaw == nil {
		c.FuncMakeRaw = rm.Enter
	}
	if c.FuncExitRaw == nil {
		c.FuncExitRaw = rm.Exit
	}
	if c.FuncOnWidthChanged == nil {
		c.FuncOnWidthChanged = platform.DefaultOnSizeChanged
	}
	if c.Painter == nil {
		c.Painter = defaultPainter
	}

	c.isInteractive = c.FuncIsTerminal()

	return nil
}

// NewFromConfig creates a readline instance from the specified configuration.
func NewFromConfig(cfg *Config) (*Instance, error) {
	if err := cfg.init(); err != nil {
		return nil, err
	}
	t, err := newTerminal(cfg)
	if err != nil {
		return nil, err
	}
	o := newOperation(t)
	return &Instance{
		terminal:  t,
		operation: o,
	}, nil
}

// NewEx is an alias for NewFromConfig, for compatibility.
var NewEx = NewFromConfig

// New creates a readline instance with default configuration.
func New(prompt string) (*Instance, error) {
	return NewFromConfig(&Config{Prompt: prompt})
}

func (i *Instance) ResetHistory() {
	i.operation.ResetHistory()
}

func (i *Instance) SetPrompt(s string) {
	cfg := i.GetConfig()
	cfg.Prompt = s
	i.SetConfig(cfg)
}

// readline will refresh automatic when write through Stdout()
func (i *Instance) Stdout() io.Writer {
	return i.operation.Stdout()
}

// readline will refresh automatic when write through Stdout()
func (i *Instance) Stderr() io.Writer {
	return i.operation.Stderr()
}

// switch VimMode in runtime
func (i *Instance) SetVimMode(on bool) {
	cfg := i.GetConfig()
	cfg.VimMode = on
	i.SetConfig(cfg)
}

func (i *Instance) IsVimMode() bool {
	return i.operation.vim.IsEnableVimMode()
}

// GeneratePasswordConfig generates a suitable Config for reading passwords;
// this config can be modified and then used with ReadLineWithConfig, or
// SetConfig.
func (i *Instance) GeneratePasswordConfig() *Config {
	return i.operation.GenPasswordConfig()
}

func (i *Instance) ReadLineWithConfig(cfg *Config) (string, error) {
	return i.operation.ReadLineWithConfig(cfg)
}

func (i *Instance) ReadPassword(prompt string) ([]byte, error) {
	if result, err := i.ReadLineWithConfig(i.GeneratePasswordConfig()); err == nil {
		return []byte(result), nil
	} else {
		return nil, err
	}
}

// ReadLine reads a line from the configured input source, allowing inline editing.
// The returned error is either nil, io.EOF, or readline.ErrInterrupt.
func (i *Instance) ReadLine() (string, error) {
	return i.operation.String()
}

// Readline is an alias for ReadLine, for compatibility.
func (i *Instance) Readline() (string, error) {
	return i.ReadLine()
}

// SetDefault prefills a default value for the next call to Readline()
// or related methods. The value will appear after the prompt for the user
// to edit, with the cursor at the end of the line.
func (i *Instance) SetDefault(defaultValue string) {
	i.operation.SetBuffer(defaultValue)
}

func (i *Instance) ReadLineWithDefault(defaultValue string) (string, error) {
	i.SetDefault(defaultValue)
	return i.operation.String()
}

// SaveToHistory adds a string to the instance's stored history. This is particularly
// relevant when DisableAutoSaveHistory is configured.
func (i *Instance) SaveToHistory(content string) error {
	return i.operation.SaveToHistory(content)
}

// same as readline
func (i *Instance) ReadSlice() ([]byte, error) {
	return i.operation.Slice()
}

// Close() closes the readline instance, cleaning up state changes to the
// terminal. It interrupts any concurrent Readline() operation, so it can be
// asynchronously or from a signal handler. It is concurrency-safe and
// idempotent, so it can be called multiple times.
func (i *Instance) Close() error {
	i.closeOnce.Do(func() {
		// TODO reorder these?
		i.operation.Close()
		i.closeErr = i.terminal.Close()
	})
	return i.closeErr
}

// CaptureExitSignal registers handlers for common exit signals that will
// close the readline instance.
func (i *Instance) CaptureExitSignal() {
	cSignal := make(chan os.Signal, 1)
	// TODO handle other signals in a portable way?
	signal.Notify(cSignal, os.Interrupt, syscall.SIGTERM)
	go func() {
		for range cSignal {
			i.Close()
		}
	}()
}

// Write writes output to the screen, redrawing the prompt and buffer
// as needed.
func (i *Instance) Write(b []byte) (int, error) {
	return i.Stdout().Write(b)
}

// GetConfig returns a copy of the current config.
func (i *Instance) GetConfig() *Config {
	cfg := i.operation.GetConfig()
	result := new(Config)
	*result = *cfg
	return result
}

// SetConfig modifies the current instance's config.
func (i *Instance) SetConfig(cfg *Config) error {
	_, err := i.operation.SetConfig(cfg)
	return err
}

// Refresh redraws the input buffer on screen.
func (i *Instance) Refresh() {
	i.operation.Refresh()
}

// DisableHistory disables the saving of input lines in history.
func (i *Instance) DisableHistory() {
	i.operation.history.Disable()
}

// EnableHistory enables the saving of input lines in history.
func (i *Instance) EnableHistory() {
	i.operation.history.Enable()
}

// ClearScreen clears the screen.
func (i *Instance) ClearScreen() {
	clearScreen(i.operation.Stdout())
}

// Painter is a callback type to allow modifying the buffer before it is rendered
// on screen, for example, to implement real-time syntax highlighting.
type Painter func(line []rune, pos int) []rune

func defaultPainter(line []rune, _ int) []rune {
	return line
}

// Listener is a callback type to listen for keypresses while the line is being
// edited. It is invoked initially with (nil, 0, 0), and then subsequently for
// any keypress until (but not including) the newline/enter keypress that completes
// the input.
type Listener func(line []rune, pos int, key rune) (newLine []rune, newPos int, ok bool)