using DocumentOperator.Application.MergePdfs;
using DocumentOperator.Domain.Common.Exceptions;
using MediatR;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;

namespace DocumentOperator.API.Controllers;

/// <summary>
/// Controller for PDF operations (merge, stamp, annotate).
/// </summary>
[ApiController]
[Route("api/pdf/operations")]
public class PdfOperationsController(IMediator mediator) : ControllerBase
{
    /// <summary>
    /// Merges multiple PDF files into a single PDF.
    /// Supports multipart/form-data file upload.
    /// </summary>
    /// <param name="files">PDF files to merge (minimum 2 required)</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>Merged PDF file</returns>
    /// <response code="200">PDFs merged successfully - returns merged PDF</response>
    /// <response code="400">Invalid input (fewer than 2 files, corrupted PDF)</response>
    /// <response code="500">Internal server error during PDF processing</response>
    [HttpPost("merge")]
    [Consumes("multipart/form-data")]
    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
    public async Task<IActionResult> MergeFromFiles(
        [FromForm] List<IFormFile> files,
        CancellationToken cancellationToken)
    {
        // Convert IFormFile[] to Stream[] (use OpenReadStream directly - no buffering)
        var streams = files.Select(f => f.OpenReadStream()).ToList();

        // Send command to MediatR (no page ranges for now - multipart binding is complex)
        var command = new MergePdfsCommand 
        { 
            PdfStreams = streams,
            PageRanges = null
        };
        
        byte[] mergedPdf = await mediator.Send(command, cancellationToken);

        // Return merged PDF
        return File(mergedPdf, "application/pdf", "merged.pdf");
    }

    /// <summary>
    /// Merges multiple PDF files into a single PDF.
    /// Supports Base64-encoded PDFs via JSON payload.
    /// </summary>
    /// <param name="request">Request containing Base64-encoded PDFs and optional page ranges</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>Merged PDF file</returns>
    /// <response code="200">PDFs merged successfully - returns merged PDF</response>
    /// <response code="400">Invalid input (Base64 format error, fewer than 2 files, corrupted PDF, invalid page range)</response>
    /// <response code="500">Internal server error during PDF processing</response>
    [HttpPost("merge")]
    [Consumes("application/json")]
    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
    public async Task<IActionResult> MergeFromBase64(
        [FromBody] MergePdfsRequest request,
        CancellationToken cancellationToken)
    {
        // Convert Base64[] to MemoryStream[]
        List<Stream> streams = new();
        try
        {
            foreach (var base64Pdf in request.Base64Pdfs)
            {
                byte[] pdfBytes = Convert.FromBase64String(base64Pdf);
                streams.Add(new MemoryStream(pdfBytes));
            }
        }
        catch (FormatException ex)
        {
            // Dispose opened streams on error
            foreach (var stream in streams) stream.Dispose();
            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
        }

        var command = new MergePdfsCommand 
        { 
            PdfStreams = streams,
            PageRanges = request.PageRanges
        };
        
        byte[] mergedPdf = await mediator.Send(command, cancellationToken);

        // Cleanup streams (important for MemoryStreams we created)
        foreach (var stream in streams) stream.Dispose();

        return File(mergedPdf, "application/pdf", "merged.pdf");
    }
}

/// <summary>
/// Request DTO for Base64-encoded PDF merge operation
/// </summary>
public record MergePdfsRequest
{
    /// <summary>
    /// Array of Base64-encoded PDF files (minimum 2 required)
    /// </summary>
    /// <example>["JVBERi0xLjQK...", "JVBERi0xLjQK..."]</example>
    public List<string> Base64Pdfs { get; init; } = new();

    /// <summary>
    /// Optional page ranges per PDF (null = all pages). 
    /// Format: "1-3,5" means pages 1, 2, 3, and 5.
    /// If provided, array length must match Base64Pdfs length.
    /// </summary>
    /// <example>["1-2", "1,3,5", null]</example>
    public List<string?>? PageRanges { get; init; }
}