using System.IO.Enumeration;

namespace AIStudio.Assistants.BatchProcessing;

public partial class AssistantBatchProcessing
{
    private string? ValidateInputDirectory(string directory)
    {
        if (string.IsNullOrWhiteSpace(directory))
            return T("Please select the folder that contains the documents you want to process.");

        if (!Directory.Exists(directory))
            return T("The selected folder does not exist.");

        return null;
    }

    private string? ValidateFilePatterns(string patterns)
    {
        if (string.IsNullOrWhiteSpace(patterns))
            return T("Please provide at least one file pattern, e.g., *.pdf. Separate multiple patterns with a semicolon.");

        return null;
    }

    private string? ValidateCsvFileName(string fileName)
    {
        if (string.IsNullOrWhiteSpace(fileName))
            return null;

        if (fileName.Trim().IndexOfAny(Path.GetInvalidFileNameChars()) >= 0)
            return T("Please provide a file name without a path, e.g., my-results.csv");

        return null;
    }

    private string? ValidateFreePrompt(string prompt)
    {
        if (this.promptSource is BatchProcessingPromptSource.FREE_PROMPT && string.IsNullOrWhiteSpace(prompt))
            return T("Please describe what the AI should do with each document.");

        return null;
    }

    /// <summary>
    /// Validates the instruction sources which have no input field of their own.
    /// </summary>
    private string? ValidateInstructionSource() => this.promptSource switch
    {
        BatchProcessingPromptSource.POLICY when this.selectedPolicy is null => T("Please select a document analysis policy."),
        BatchProcessingPromptSource.FILE_IMPORT when string.IsNullOrWhiteSpace(this.importedPrompt) => T("Please select the file which contains your instructions."),

        _ => null,
    };

    private string? ValidatingProviderWithBatchState(AIStudio.Settings.Provider provider)
    {
        if (this.isProcessingBatch)
            return null;

        return this.ValidatingProvider(provider);
    }

    private string ResolveOutputDirectory()
    {
        if (string.IsNullOrWhiteSpace(this.outputDirectory))
            return Path.Join(this.inputDirectory, DEFAULT_OUTPUT_DIRECTORY_NAME);

        return this.outputDirectory;
    }

    private IReadOnlyList<string> FindInputFiles(string resolvedOutputDirectory)
    {
        var patterns = this.filePatterns
            .Split(';', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
            .ToList();

        var searchOption = this.includeSubdirectories ? SearchOption.AllDirectories : SearchOption.TopDirectoryOnly;
        var files = new SortedSet<string>(StringComparer.OrdinalIgnoreCase);

        var normalizedInputDirectory = TrimDirectorySeparator(Path.GetFullPath(this.inputDirectory));
        var normalizedOutputDirectory = TrimDirectorySeparator(Path.GetFullPath(resolvedOutputDirectory));

        // When the output folder is a folder of its own, we skip everything
        // inside it. When it is the input folder itself, we must not skip the
        // whole folder: we would not find any document at all. We then skip
        // our own output artifacts instead.
        var isOutputSeparateFolder = !string.Equals(normalizedInputDirectory, normalizedOutputDirectory, StringComparison.OrdinalIgnoreCase);

        // The separator is essential: without it, an output folder named 'out'
        // would also exclude a document named 'output-notes.md':
        var outputDirectoryPrefix = normalizedOutputDirectory + Path.DirectorySeparatorChar;

        foreach (var pattern in patterns)
        {
            foreach (var file in Directory.EnumerateFiles(this.inputDirectory, pattern, searchOption))
            {
                var normalizedFile = Path.GetFullPath(file);
                if (isOutputSeparateFolder)
                {
                    if (normalizedFile.StartsWith(outputDirectoryPrefix, StringComparison.OrdinalIgnoreCase))
                        continue;
                }
                else if (this.IsOwnOutputArtifact(normalizedFile))
                    continue;

                // On Windows, a pattern with a three-character extension also
                // matches longer extensions: '*.pdf' also returns 'report.pdfx'.
                // We therefore check the pattern ourselves:
                if (!MatchesAnyPattern(normalizedFile, patterns))
                    continue;

                files.Add(normalizedFile);
            }
        }

        return [.. files];
    }

    private static string TrimDirectorySeparator(string path) => path.TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);

    private static bool MatchesAnyPattern(string filePath, IReadOnlyList<string> patterns)
    {
        var fileName = Path.GetFileName(filePath);
        foreach (var pattern in patterns)
        {
            // A pattern may contain a folder part, which does not take part in
            // matching the file name:
            var namePattern = Path.GetFileName(pattern);
            if (string.IsNullOrWhiteSpace(namePattern))
                continue;

            if (FileSystemName.MatchesSimpleExpression(namePattern, fileName))
                return true;
        }

        return false;
    }

    /// <summary>
    /// Checks whether a file is an output artifact of this assistant. We need
    /// this when the output folder is the input folder: without it, the results
    /// of a previous run would be processed as documents.
    /// </summary>
    private bool IsOwnOutputArtifact(string filePath)
    {
        var fileName = Path.GetFileName(filePath);
        if (string.Equals(fileName, LOG_FILENAME, StringComparison.OrdinalIgnoreCase))
            return true;

        if (string.Equals(fileName, this.ResolveResultsFileName(), StringComparison.OrdinalIgnoreCase))
            return true;

        return fileName.EndsWith(RESULT_FILE_SUFFIX, StringComparison.OrdinalIgnoreCase);
    }

    /// <summary>
    /// Validates the form, finds the documents, and creates the output folder.
    /// </summary>
    /// <returns>The output folder and the documents, or <c>null</c> when the run must not start.</returns>
    private async Task<(string ResolvedOutputDirectory, IReadOnlyList<string> Files)?> PrepareRunAsync()
    {
        await this.Form!.Validate();

        var instructionIssue = this.ValidateInstructionSource();
        if (instructionIssue is not null)
        {
            this.AddInputIssue(instructionIssue);
            return null;
        }

        if (!this.InputIsValid)
            return null;

        var resolvedOutputDirectory = this.ResolveOutputDirectory();
        IReadOnlyList<string> files;
        try
        {
            files = this.FindInputFiles(resolvedOutputDirectory);
        }
        catch (Exception e)
        {
            this.AddInputIssue(string.Format(T("Was not able to read the input folder: {0}"), e.Message));
            return null;
        }

        if (files.Count == 0)
        {
            this.AddInputIssue(T("No matching files were found in the selected folder."));
            return null;
        }

        try
        {
            Directory.CreateDirectory(resolvedOutputDirectory);
        }
        catch (Exception e)
        {
            this.AddInputIssue(string.Format(T("Was not able to create the output folder: {0}"), e.Message));
            return null;
        }

        return (resolvedOutputDirectory, files);
    }
}