using System.Text;
using DataModel.Database;

namespace Processor.Generators;

public class DotnetBigFile : IGenerator
{
    private static readonly List<string> CULTURE_CODES = new();
    private static int DEFAULT_CULTURE_INDEX = -1; 

    public async Task<ProcessorResult<long>> GenerateAsync()
    {
        const string filename = "I18N.cs";
        
        var destPath = await AppSettings.GetGeneratorDotnetDestinationPath();
        destPath = Environment.ExpandEnvironmentVariables(destPath);
        long destBytesWritten = 0;
        
        var pathFinal = Path.Join(destPath, filename);
        var pathTemp = Path.Join(destPath, filename + ".gen");
        var issueFinal = string.Empty;

        try
        {
            if(File.Exists(pathTemp))
                File.Delete(pathTemp);
        }
        catch (IOException e)
        {
            return new ProcessorResult<long>(0, false, $"Cannot delete the temporary file: '{e.Message}'. Hint: Is the ransomware protection enabled in your Windows system? If so, please make sure that the I18N Commander has write permission.");
        }

        CULTURE_CODES.Clear();
        var cultures = await AppSettings.GetCultureInfos();
        foreach (var (code, _) in cultures)
            CULTURE_CODES.Add(code);

        DEFAULT_CULTURE_INDEX = await AppSettings.GetGeneratorDotnetDefaultCultureIndex();
        DEFAULT_CULTURE_INDEX -= 1; // 1-based to 0-based

        try
        {
            await using var fileStream = new FileStream(pathTemp, FileMode.CreateNew, FileAccess.Write, FileShare.None);
            await using var writer = new StreamWriter(fileStream, Encoding.UTF8);

            await writer.WriteLineAsync("""using System.Globalization;""");
            await writer.WriteLineAsync($"""namespace {await AppSettings.GetGeneratorDotnetNamespace()};""");
            await this.CreateStaticClass(writer, "I18N", 0, async (streamWriter, indention) =>
            {
                var indentionString = this.AddIndention(indention);
                var buildTime = DateTime.UtcNow;
                await writer.WriteLineAsync($"{indentionString}public static readonly string BUILD_TIME = \"{buildTime:yyyy.MM.dd HH:mm:ss}\";");
                await writer.WriteLineAsync($"{indentionString}public static readonly long BUILD_TIME_TICKS = {buildTime.Ticks};");

                // Go through the first layer of sections:
                var sections = await SectionProcessor.LoadLayer(0);
                foreach (var section in sections)
                    await this.TransformSection(writer, indention, section);
            });
        }
        catch (IOException e)
        {
            // Happens, e.g. when the ransomware protection on Windows is active and
            // the I18N commander is not on the exclusion list.
            return new ProcessorResult<long>(0, false, $"Cannot write the generator's result file: '{e.Message}'. Hint: Is the ransomware protection enabled in your Windows system? If so, please make sure that the I18N Commander has write permission.");
        }
        finally
        {
            if (File.Exists(pathTemp))
            {
                destBytesWritten = new FileInfo(pathTemp).Length;
                if (destBytesWritten > 0)
                {
                    try
                    {
                        if (File.Exists(pathFinal))
                            File.Delete(pathFinal);

                        File.Move(pathTemp, pathFinal);
                    }
                    catch (IOException e)
                    {
                        // Happens when the file is still in use by the compiler, the IDE, etc.
                        // Depends on the timing, this happens sometimes. We ignore it, though.
                        issueFinal = e.Message;
                    }
                }
            }
        }

        if(string.IsNullOrWhiteSpace(issueFinal))
            return new ProcessorResult<long>(destBytesWritten, true, string.Empty);
        else
            return new ProcessorResult<long>(0, false, $"Cannot move the generator's result file to the destination: '{issueFinal}'. Hint: Is the ransomware protection enabled in your Windows system? If so, please make sure that the I18N Commander has write permission.");
    }

    private string AddIndention(int indention) => new string(' ', indention * 3);

    private async Task TransformSection(TextWriter writer, int indention, Section section)
    {
        await this.CreateStaticClass(writer, section.DataKey, indention, async (_, innerIndention) =>
        {
            var textElements = section.TextElements;
            foreach (var textElement in textElements)
                    await this.TransformTextElement(writer, innerIndention, textElement);

            var childSections = await SectionProcessor.GetChildSections(section.DataKey);
            foreach (var childSection in childSections)
                await this.TransformSection(writer, innerIndention, childSection);
        });
    }
    
    private async Task TransformTextElement(TextWriter writer, int indention, TextElement textElement)
    {
        var indentionString = this.AddIndention(indention);
        var indentionInner1 = this.AddIndention(indention + 1);
        var indentionInner2 = this.AddIndention(indention + 2);

        await writer.WriteLineAsync($"""{indentionString}public static string E_{textElement.Code}() => E_{textElement.Code}(CultureInfo.CurrentCulture);""");
        await writer.WriteLineAsync($"""{indentionString}public static string E_{textElement.Code}(CultureInfo culture)""");
        await writer.WriteLineAsync($$"""{{indentionString}}{"""); // opening {

        // Write the default culture's text:
        var defaultCultureTranslation = textElement.Translations.FirstOrDefault(x => x.Culture == CULTURE_CODES[DEFAULT_CULTURE_INDEX]);
        var defaultCultureText = defaultCultureTranslation?.Text ?? string.Empty;
        await this.WriteTextContent(writer, indentionInner1, textElement.IsMultiLine, defaultCultureText, variableName: "defaultText");
        
        await writer.WriteLineAsync($"""{indentionInner1}var name = culture.Name;""");
        await writer.WriteLineAsync($"""{indentionInner1}if(name.Length < 2)""");
        await writer.WriteLineAsync($$"""{{indentionInner1}}{"""); // opening {
        await writer.WriteLineAsync($"""{indentionInner2}return defaultText;""");
        await writer.WriteLineAsync($$"""{{indentionInner1}}}"""); // closing }
        
        for (var cultureIndex = 0; cultureIndex < CULTURE_CODES.Count; cultureIndex++)
        {
            await writer.WriteLineAsync($"""{indentionInner1}if ({this.CreateIf(CULTURE_CODES[cultureIndex])})""");
            await writer.WriteLineAsync($$"""{{indentionInner1}}{"""); // opening {
            
            if(cultureIndex == DEFAULT_CULTURE_INDEX)
                await writer.WriteLineAsync($"""{indentionInner2}return defaultText;""");
            else
            {
                var cultureTranslation = textElement.Translations.FirstOrDefault(x => x.Culture == CULTURE_CODES[cultureIndex]);
                var cultureText = cultureTranslation?.Text ?? string.Empty;
                await this.WriteTextContent(writer, indentionInner2, textElement.IsMultiLine, cultureText);
                await writer.WriteLineAsync($"""{indentionInner2}return text;""");
            }

            await writer.WriteLineAsync($$"""{{indentionInner1}}}"""); // closing }            
        }
        
        // Add the default case:
        await writer.WriteLineAsync($"""{indentionInner1}return defaultText;""");
        await writer.WriteLineAsync($$"""{{indentionString}}}"""); // closing }
        await writer.WriteLineAsync();
    }
    
    private async Task CreateStaticClass(TextWriter writer, string name, int indention, Func<TextWriter, int, Task> content)    
    {
        var indentionString = this.AddIndention(indention);

        await writer.WriteLineAsync(indentionString);
        await writer.WriteLineAsync($"{indentionString}public static class {name}");
        await writer.WriteLineAsync($"{indentionString}{{");
        await content(writer, indention + 1);
        await writer.WriteLineAsync($"{indentionString}}}");
    }

    private async Task WriteTextContent(TextWriter writer, string indention, bool isMultiline, string content, string variableName = "text")
    {
        if(isMultiline)
        {
            await writer.WriteLineAsync($"""""""""
{indention}const string {variableName} = """"""""
""""""""");
            await writer.WriteLineAsync(content);
            await writer.WriteLineAsync($"""""""""
"""""""";
""""""""");
        }
        else
            await writer.WriteLineAsync($"""""""""{indention}const string {variableName} = """"""""{content}"""""""";""""""""");
    }

    private string CreateIf(string cultureCode)
    {
        if (string.IsNullOrWhiteSpace(cultureCode))
            return "false";

        var sb = new StringBuilder();
        var len = cultureCode.Length;
        if (len > 2)
            sb.Append($"""name.Length >= {len} && """);
        
        for (var i = 0; i < cultureCode.Length; i++)
        {
            sb.Append($"""name[{i}] is '{cultureCode[i]}'""");
            
            // When this is not the last character, we need to add " && ":
            if (i < cultureCode.Length - 1)
                sb.Append(" && ");
        }

        return sb.ToString();
    }
}