using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;

namespace DrillTools
{
    internal static class DrillTapeParameterCleaner
    {
        private const int Gb2312CodePage = 936;
        private static readonly char[] LineEndChars = { '\r', '\n' };
        private static readonly Regex HeaderToolDefinitionStartPattern = new(
            @"^T\d+C",
            RegexOptions.Compiled | RegexOptions.IgnoreCase);
        private static readonly Regex ToolDefinitionPattern = new(
            @"^(?<prefix>\s*T\d+C\d+(?:\.\d+)?)(?<parameters>H.+)$",
            RegexOptions.Compiled | RegexOptions.IgnoreCase);

        public static bool CanClearParameters(string drillTapeContent)
        {
            var lines = SplitLines(drillTapeContent);
            if (lines.Count < 2)
                return false;

            string secondLine = lines[1].Text.Trim();
            if (!secondLine.StartsWith(";") || secondLine.Length == 1)
                return false;

            var toolDefinitionLines = GetHeaderToolDefinitionLines(lines);
            if (toolDefinitionLines.Count == 0)
                return false;

            foreach (var line in toolDefinitionLines)
            {
                if (!ToolDefinitionPattern.IsMatch(line.Text.TrimEnd()))
                    return false;
            }

            return true;
        }

        public static string ClearParameters(string drillTapeContent)
        {
            if (!CanClearParameters(drillTapeContent))
                throw new InvalidOperationException("钻带文件不符合清空参数条件");

            var lines = SplitLines(drillTapeContent);
            var builder = new StringBuilder(drillTapeContent.Length);

            for (int i = 0; i < lines.Count; i++)
            {
                if (i == 1)
                    continue;

                string text = lines[i].Text;
                var match = ToolDefinitionPattern.Match(text.TrimEnd());
                if (match.Success && IsBeforeHeaderEnd(lines, i))
                {
                    int trailingWhitespaceLength = text.Length - text.TrimEnd().Length;
                    string trailingWhitespace = trailingWhitespaceLength > 0 ? text[^trailingWhitespaceLength..] : string.Empty;
                    text = match.Groups["prefix"].Value + trailingWhitespace;
                }

                builder.Append(text);
                builder.Append(lines[i].LineEnding);
            }

            return builder.ToString();
        }

        public static void ClearParametersAndSave(string filePath)
        {
            string content = CommandTypeFileReader.ReadAllText(filePath);
            string cleanedContent = ClearParameters(content);

            string backupFilePath = filePath + ".bak";
            File.Copy(filePath, backupFilePath, true);

            using var writer = new StreamWriter(filePath, false, CreateAnsiEncoding());
            writer.Write(cleanedContent);
        }

        private static List<DrillTapeLine> SplitLines(string content)
        {
            var lines = new List<DrillTapeLine>();
            int index = 0;

            while (index < content.Length)
            {
                int lineEndIndex = content.IndexOfAny(LineEndChars, index);
                if (lineEndIndex < 0)
                {
                    lines.Add(new DrillTapeLine(content[index..], string.Empty));
                    return lines;
                }

                string text = content[index..lineEndIndex];
                string lineEnding;
                if (content[lineEndIndex] == '\r' && lineEndIndex + 1 < content.Length && content[lineEndIndex + 1] == '\n')
                {
                    lineEnding = "\r\n";
                    index = lineEndIndex + 2;
                }
                else
                {
                    lineEnding = content[lineEndIndex].ToString();
                    index = lineEndIndex + 1;
                }

                lines.Add(new DrillTapeLine(text, lineEnding));
            }

            if (content.Length == 0)
                lines.Add(new DrillTapeLine(string.Empty, string.Empty));

            return lines;
        }

        private static List<DrillTapeLine> GetHeaderToolDefinitionLines(IReadOnlyList<DrillTapeLine> lines)
        {
            var toolDefinitionLines = new List<DrillTapeLine>();

            foreach (var line in lines)
            {
                string trimmedLine = line.Text.Trim();
                if (trimmedLine == "%")
                    break;

                if (HeaderToolDefinitionStartPattern.IsMatch(trimmedLine))
                    toolDefinitionLines.Add(line);
            }

            return toolDefinitionLines;
        }

        private static bool IsBeforeHeaderEnd(IReadOnlyList<DrillTapeLine> lines, int lineIndex)
        {
            for (int i = 0; i < lineIndex; i++)
            {
                if (lines[i].Text.Trim() == "%")
                    return false;
            }

            return true;
        }

        private static Encoding CreateAnsiEncoding()
        {
            return Encoding.GetEncoding(Gb2312CodePage);
        }

        private readonly record struct DrillTapeLine(string Text, string LineEnding);
    }
}