/********************************************************************++
Copyright (c) Microsoft Corporation.  All rights reserved.
--********************************************************************/

using System;
using System.Diagnostics;
using System.Management.Automation.Language;

namespace Microsoft.PowerShell
{
    public partial class PSConsoleReadLine
    {
        private int _moveToEndOfLineCommandCount;
        private int _moveToLineCommandCount;
        private int _moveToLineDesiredColumn;

        /// <summary>
        /// If the input has multiple lines, move to the end of the current line,
        /// or if already at the end of the line, move to the end of the input.
        /// If the input has a single line, move to the end of the input.
        /// </summary>
        public static void EndOfLine(ConsoleKeyInfo? key = null, object arg = null)
        {
            int i = _singleton._current;
            for (; i < _singleton._buffer.Length; i++)
            {
                if (_singleton._buffer[i] == '\n')
                {
                    break;
                }
            }

            _singleton.MoveCursor((i == _singleton._current) ? _singleton._buffer.Length : i);
        }

        /// <summary>
        /// If the input has multiple lines, move to the start of the current line,
        /// or if already at the start of the line, move to the start of the input.
        /// If the input has a single line, move to the start of the input.
        /// </summary>
        public static void BeginningOfLine(ConsoleKeyInfo? key = null, object arg = null)
        {
            var newCurrent = GetBeginningOfLinePos(_singleton._current);
            newCurrent = newCurrent == _singleton._current ? 0 : newCurrent;

            _singleton.MoveCursor(newCurrent);
        }

        /// <summary>
        /// Move the cursor one character to the right.  This may move the cursor to the next
        /// line of multi-line input.
        /// </summary>
        public static void ForwardChar(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (TryGetArgAsInt(arg, out var numericArg, 1))
            {
                if (_singleton._current == _singleton._buffer.Length && numericArg > 0)
                {
                    AcceptSuggestion(key, arg);
                }
                else
                {
                    SetCursorPosition(_singleton._current + numericArg);
                }
            }
        }

        /// <summary>
        /// Move the cursor one character to the left.  This may move the cursor to the previous
        /// line of multi-line input.
        /// </summary>
        public static void BackwardChar(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (TryGetArgAsInt(arg, out var numericArg, 1))
            {
                SetCursorPosition(_singleton._current - numericArg);
            }
        }

        /// <summary>
        /// Moves the cursor one character to the right on a single logical line.
        /// </summary>
        public static void ViForwardChar(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (TryGetArgAsInt(arg, out var numericArg, 1))
            {
                if (InViInsertMode() && _singleton._current == _singleton._buffer.Length && numericArg > 0)
                {
                    AcceptSuggestion(key, arg);
                }
                else
                {
                    ViOffsetCursorPosition(+numericArg);
                }
            }
        }

        /// <summary>
        /// Move the cursor one character to the left on a single logical line.
        /// </summary>
        public static void ViBackwardChar(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (TryGetArgAsInt(arg, out var numericArg, 1))
            {
                ViOffsetCursorPosition(-numericArg);
            }
        }

        /// <summary>
        /// Moves the cursor to the left or right a certain number of characters.
        /// If the count is negative, moves the cursor in the left direction.
        /// </summary>
        private static void ViOffsetCursorPosition(int count)
        {
            if (count < 0)
            {
                var start = GetBeginningOfLinePos(_singleton._current);
                var newCurrent = Math.Max(start, _singleton._current + count);
                if (_singleton._current != newCurrent)
                {
                    _singleton.MoveCursor(newCurrent);
                }
            }
            else if (_singleton._current < _singleton._buffer.Length)
            {
                // when in the VI command mode, 'end' is the position of the last character;
                // when in the VI insert mode, 'end' is 1 char beyond the last character.
                var end = GetEndOfLogicalLinePos(_singleton._current) + 1 + ViEndOfLineFactor;
                var newCurrent = Math.Min(end, _singleton._current + count);
                if (_singleton._current != newCurrent)
                {
                    _singleton.MoveCursor(newCurrent);
                }
            }
        }

        private void MoveToLine(int lineOffset)
        {
            if (InViCommandMode())
            {
                ViMoveToLine(lineOffset);
            }
            else
            {
                MoveToLineImpl(lineOffset);
            }
        }

        private void MoveToLineImpl(int lineOffset)
        {
            // Behavior description:
            //  - If the cursor is at the end of a logical line, then 'UpArrow' (or 'DownArrow') moves the cursor up (or down)
            //    'lineOffset' numbers of logical lines, and the cursor is always put at the end of the new logical line.
            //  - If the cursor is NOT at the end of a logical line, then 'UpArrow' (or 'DownArrow') moves the cursor up (or down)
            //    'lineOffset' numbers of physical lines, and the cursor is always placed at the same column as is now, or at the
            //    end of line if that physical line is shorter than the targeted column.

            const int endOfLine = int.MaxValue;

            Point? point = null;
            _moveToLineCommandCount += 1;

            if (_moveToLineCommandCount == 1)
            {
                point = ConvertOffsetToPoint(_current);
                _moveToLineDesiredColumn =
                    (_current == _buffer.Length || _buffer[_current] == '\n')
                        ? endOfLine
                        : point.Value.X;
            }

            // Nothing needs to be done when:
            //  - actually not moving the line, or
            //  - moving the line down when it's at the end of the last line.
            if (lineOffset == 0 || (lineOffset > 0 && _current == _buffer.Length))
            {
                return;
            }

            int newCurrent;
            if (_moveToLineDesiredColumn == endOfLine)
            {
                newCurrent = _current;

                if (lineOffset > 0)
                {
                    // Moving to the end of a subsequent logical line.
                    for (int i = 0; i < lineOffset; i++)
                    {
                        for (newCurrent++; newCurrent < _buffer.Length && _buffer[newCurrent] != '\n'; newCurrent++) ;

                        if (newCurrent == _buffer.Length)
                        {
                            break;
                        }
                    }
                }
                else
                {
                    // Moving to the end of a previous logical line.
                    int lastEndOfLineIndex = _current;
                    for (int i = 0; i < -lineOffset; i++)
                    {
                        for (newCurrent--; newCurrent >= 0 && _buffer[newCurrent] != '\n'; newCurrent--) ;

                        if (newCurrent < 0)
                        {
                            newCurrent = lastEndOfLineIndex;
                            break;
                        }

                        lastEndOfLineIndex = newCurrent;
                    }
                }
            }
            else
            {
                point = point ?? ConvertOffsetToPoint(_current);
                int newY = point.Value.Y + lineOffset;

                Point newPoint = new Point()
                {
                    X = _moveToLineDesiredColumn,
                    Y = Math.Max(newY, _initialY)
                };

                newCurrent = ConvertLineAndColumnToOffset(newPoint);
            }

            if (newCurrent != -1)
            {
                MoveCursor(newCurrent);
            }
        }

        /// <summary>
        /// Move the cursor to the previous line.
        /// </summary>
        public static void PreviousLine(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (TryGetArgAsInt(arg, out var numericArg, 1))
            {
                _singleton.MoveToLine(-numericArg);
            }
        }

        /// <summary>
        /// Move the cursor to the next line.
        /// </summary>
        public static void NextLine(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (TryGetArgAsInt(arg, out var numericArg, 1))
            {
                _singleton.MoveToLine(numericArg);
            }
        }

        /// <summary>
        /// Move the cursor forward to the start of the next word.
        /// Word boundaries are defined by a configurable set of characters.
        /// </summary>
        public static void NextWord(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (!TryGetArgAsInt(arg, out var numericArg, 1))
            {
                return;
            }

            if (numericArg < 0)
            {
                BackwardWord(key, -numericArg);
                return;
            }

            while (numericArg-- > 0)
            {
                _singleton.MoveCursor(_singleton.FindNextWordPoint(_singleton.Options.WordDelimiters));
            }
        }

        /// <summary>
        /// Move the cursor forward to the end of the current word, or if between words,
        /// to the end of the next word.  Word boundaries are defined by PowerShell tokens.
        /// </summary>
        public static void ShellNextWord(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (!TryGetArgAsInt(arg, out var numericArg, 1))
            {
                return;
            }

            if (numericArg < 0)
            {
                ShellBackwardWord(key, -numericArg);
                return;
            }

            while (numericArg-- > 0)
            {
                var token = _singleton.FindToken(_singleton._current, FindTokenMode.Next);

                Debug.Assert(token != null, "We'll always find EOF");

                _singleton.MoveCursor(token.Kind == TokenKind.EndOfInput
                    ? _singleton._buffer.Length
                    : token.Extent.StartOffset);
            }
        }

        /// <summary>
        /// Move the cursor forward to the end of the current word, or if between words,
        /// to the end of the next word.  Word boundaries are defined by a configurable
        /// set of characters.
        /// </summary>
        public static void ForwardWord(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (!TryGetArgAsInt(arg, out var numericArg, 1))
            {
                return;
            }

            if (_singleton._current == _singleton._buffer.Length && numericArg > 0)
            {
                AcceptNextSuggestionWord(numericArg);
                return;
            }

            if (numericArg < 0)
            {
                BackwardWord(key, -numericArg);
                return;
            }

            while (numericArg-- > 0)
            {
                _singleton.MoveCursor(_singleton.FindForwardWordPoint(_singleton.Options.WordDelimiters));
            }
        }

        /// <summary>
        /// Move the cursor forward to the start of the next word.
        /// Word boundaries are defined by PowerShell tokens.
        /// </summary>
        public static void ShellForwardWord(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (!TryGetArgAsInt(arg, out var numericArg, 1))
            {
                return;
            }

            if (numericArg < 0)
            {
                ShellBackwardWord(key, -numericArg);
                return;
            }

            while (numericArg-- > 0)
            {
                var token = _singleton.FindToken(_singleton._current, FindTokenMode.CurrentOrNext);

                Debug.Assert(token != null, "We'll always find EOF");

                _singleton.MoveCursor(token.Kind == TokenKind.EndOfInput
                    ? _singleton._buffer.Length
                    : token.Extent.EndOffset);
            }
        }

        private static bool CheckIsBound(Action<ConsoleKeyInfo?, object> action)
        {
            foreach (var entry in _singleton._dispatchTable)
            {
                if (entry.Value.Action == action)
                    return true;
            }
            return false;
        }

        /// <summary>
        /// Move the cursor back to the start of the current word, or if between words,
        /// the start of the previous word.  Word boundaries are defined by a configurable
        /// set of characters.
        /// </summary>
        public static void BackwardWord(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (!TryGetArgAsInt(arg, out var numericArg, 1))
            {
                return;
            }

            if (numericArg < 0)
            {
                if (CheckIsBound(ForwardWord))
                {
                    ForwardWord(key, -numericArg);
                }
                else
                {
                    NextWord(key, -numericArg);
                }
                return;
            }

            while (numericArg-- > 0)
            {
                _singleton.MoveCursor(_singleton.FindBackwardWordPoint(_singleton.Options.WordDelimiters));
            }
        }

        /// <summary>
        /// Move the cursor back to the start of the current word, or if between words,
        /// the start of the previous word.  Word boundaries are defined by PowerShell tokens.
        /// </summary>
        public static void ShellBackwardWord(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (!TryGetArgAsInt(arg, out var numericArg, 1))
            {
                return;
            }

            if (numericArg < 0)
            {
                if (CheckIsBound(ShellForwardWord))
                {
                    ShellForwardWord(key, -numericArg);
                }
                else
                {
                    ShellNextWord(key, -numericArg);
                }
                return;
            }

            while (numericArg-- > 0)
            {
                var token = _singleton.FindToken(_singleton._current, FindTokenMode.Previous);
                _singleton.MoveCursor(token?.Extent.StartOffset ?? 0);
            }
        }

        /// <summary>
        /// Go to the matching brace, paren, or square bracket.
        /// </summary>
        public static void GotoBrace(ConsoleKeyInfo? key = null, object arg = null)
        {
            if (_singleton._current >= _singleton._buffer.Length)
            {
                Ding();
                return;
            }

            _singleton.MaybeParseInput();

            Token token = null;
            var index = 0;
            for (; index < _singleton._tokens.Length; index++)
            {
                token = _singleton._tokens[index];
                if (token.Extent.StartOffset == _singleton._current)
                    break;
            }

            TokenKind toMatch;
            int direction;
            switch (token.Kind)
            {
                case TokenKind.LParen: toMatch = TokenKind.RParen; direction = 1; break;
                case TokenKind.LCurly: toMatch = TokenKind.RCurly; direction = 1; break;
                case TokenKind.LBracket: toMatch = TokenKind.RBracket; direction = 1; break;

                case TokenKind.RParen: toMatch = TokenKind.LParen; direction = -1; break;
                case TokenKind.RCurly: toMatch = TokenKind.LCurly; direction = -1; break;
                case TokenKind.RBracket: toMatch = TokenKind.LBracket; direction = -1; break;

                default:
                    // Nothing to match (don't match inside strings/comments)
                    Ding();
                    return;
            }

            var matchCount = 0;
            var limit = (direction > 0) ? _singleton._tokens.Length - 1 : -1;
            for (; index != limit; index += direction)
            {
                var t = _singleton._tokens[index];
                if (t.Kind == token.Kind)
                {
                    matchCount++;
                }
                else if (t.Kind == toMatch)
                {
                    matchCount--;
                    if (matchCount == 0)
                    {
                        _singleton.MoveCursor(t.Extent.StartOffset);
                        return;
                    }
                }
            }
            Ding();
        }

        /// <summary>
        /// Clear the screen and draw the current line at the top of the screen.
        /// </summary>
        public static void ClearScreen(ConsoleKeyInfo? key = null, object arg = null)
        {
            var console = _singleton._console;
            console.Write("\x1b[2J");
            InvokePrompt(null, console.WindowTop);
        }

        // Try to convert the arg to a char, return 0 for failure
        private static char TryGetArgAsChar(object arg)
        {
            if (arg is char c)
            {
                return c;
            }

            if (arg is string s && s.Length == 1)
            {
                return s[0];
            }

            return '\0';
        }

        /// <summary>
        /// Read a character and search forward for the next occurrence of that character.
        /// If an argument is specified, search forward (or backward if negative) for the
        /// nth occurrence.
        /// </summary>
        public static void CharacterSearch(ConsoleKeyInfo? key = null, object arg = null)
        {
            int occurrence = arg as int? ?? 1;
            if (occurrence < 0)
            {
                CharacterSearchBackward(key, -occurrence);
                return;
            }

            char toFind = TryGetArgAsChar(arg);
            if (toFind == '\0')
            {
                // Should we prompt?
                toFind = ReadKey().KeyChar;
            }
            for (int i = _singleton._current + 1; i < _singleton._buffer.Length; i++)
            {
                if (_singleton._buffer[i] == toFind)
                {
                    occurrence -= 1;
                    if (occurrence == 0)
                    {
                        _singleton.MoveCursor(i);
                        break;
                    }
                }
            }
            if (occurrence > 0)
            {
                Ding();
            }
        }

        /// <summary>
        /// Read a character and search backward for the next occurrence of that character.
        /// If an argument is specified, search backward (or forward if negative) for the
        /// nth occurrence.
        /// </summary>
        public static void CharacterSearchBackward(ConsoleKeyInfo? key = null, object arg = null)
        {
            int occurrence = arg as int? ?? 1;
            if (occurrence < 0)
            {
                CharacterSearch(key, -occurrence);
                return;
            }

            char toFind = TryGetArgAsChar(arg);
            if (toFind == '\0')
            {
                // Should we prompt?
                toFind = ReadKey().KeyChar;
            }
            for (int i = _singleton._current - 1; i >= 0; i--)
            {
                if (_singleton._buffer[i] == toFind)
                {
                    occurrence -= 1;
                    if (occurrence == 0)
                    {
                        _singleton.MoveCursor(i);
                        return;
                    }
                }
            }
            Ding();
        }
    }
}