package download

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"

	"rhemawavetech.com/rhemawave/internal/logger"
)

// DownloadStatus holds information related to downloads and is
// the container for information returned via channels within this
// package.
type DownloadStatus struct {
	Max int64  // Total bytes to download
	Cur int64  // Total bytes downloaded
	Msg string // Status message
	Err error  // Error, if any
}

// DownloadAudioFiles downloads multiple audio files and sends progress updates
// to the provided channel. The channel is closed when all downloads are complete.
func DownloadAudioFiles(progressChan chan<- DownloadStatus, filenames []string, destDir string) {
	defer close(progressChan)

	urlBase := "https://files.rhemawavetech.com/audio/"

	// First, calculate the total size of files that need to be downloaded
	totalSize := int64(0)
	filesToDownload := []string{}
	totalDownloaded := int64(0)

	for _, filename := range filenames {
		destPath := filepath.Join(destDir, filename)
		// Check if the file already exists
		url := urlBase + filename
		resp, err := http.Head(url)
		if err != nil {
			progressChan <- DownloadStatus{
				Msg: fmt.Sprintf("Failed to get size for %s: %v", filename, err),
				Err: err,
			}
			return
		}
		if resp.StatusCode != http.StatusOK {
			progressChan <- DownloadStatus{
				Msg: fmt.Sprintf("Failed to get size for %s: status %s", filename, resp.Status),
				Err: fmt.Errorf("bad status: %s", resp.Status),
			}
			return
		}
		fileStat, err := os.Stat(destPath)
		// If the file is incomplete, or does not exist
		if os.IsNotExist(err) || fileStat.Size() != resp.ContentLength {
			// Oh, and log a warning if the file is not complete
			if !os.IsNotExist(err) {
				logger.Warning("%s incomplete/corrupt. Adding to download queue.", filename)
			} else {
				logger.Info("%s not found. Adding to download queue.", filename)
			}

			// Append it to the list to download
			filesToDownload = append(filesToDownload, filename)
		} else if err != nil {
			logger.Error("unknown error: %v", err)
		} else {
			logger.Error("File %s exists, skipping...", filename)
			totalDownloaded += fileStat.Size()
		}
		// Calculate the total of ALL files to give the illusion of
		// "picking up where you left off" to the user
		totalSize += resp.ContentLength
		resp.Body.Close()
	}

	// Send initial status
	progressChan <- DownloadStatus{
		Max: totalSize,
		Cur: 0,
		Msg: "Starting download...",
	}

	// Download each file that doesn't exist
	for _, filename := range filesToDownload {
		url := urlBase + filename
		destPath := filepath.Join(destDir, filename)

		// Create the destination file
		out, err := os.Create(destPath)
		if err != nil {
			progressChan <- DownloadStatus{
				Msg: fmt.Sprintf("Failed to create file %s: %v", destPath, err),
				Err: err,
			}
			return
		}

		// Get the file
		resp, err := http.Get(url)
		if err != nil {
			out.Close()
			os.Remove(destPath)
			progressChan <- DownloadStatus{
				Msg: fmt.Sprintf("Failed to download %s: %v", filename, err),
				Err: err,
			}
			return
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			out.Close()
			os.Remove(destPath)
			progressChan <- DownloadStatus{
				Msg: fmt.Sprintf("Failed to download %s: status %s", filename, resp.Status),
				Err: fmt.Errorf("bad status: %s", resp.Status),
			}
			return
		}

		// Use a buffered reader for efficiency
		buf := make([]byte, 8192)
		for {
			n, err := resp.Body.Read(buf)
			if err != nil && err != io.EOF {
				out.Close()
				os.Remove(destPath)
				progressChan <- DownloadStatus{
					Msg: fmt.Sprintf("Failed to read %s: %v", filename, err),
					Err: err,
				}
				return
			}
			if n == 0 {
				break
			}

			// Write to file
			if _, err := out.Write(buf[:n]); err != nil {
				out.Close()
				os.Remove(destPath)
				progressChan <- DownloadStatus{
					Msg: fmt.Sprintf("Failed to write %s: %v", filename, err),
					Err: err,
				}
				return
			}

			// Update progress
			totalDownloaded += int64(n)
			progressChan <- DownloadStatus{
				Max: totalSize,
				Cur: totalDownloaded,
				Msg: fmt.Sprintf("%s", filename),
			}
		}

		out.Close()

		// Send completion for this file
		progressChan <- DownloadStatus{
			Max: totalSize,
			Cur: totalDownloaded,
			Msg: "Finished Downloading",
		}
	}

	// Send final status
	progressChan <- DownloadStatus{
		Max: totalSize,
		Cur: totalDownloaded,
		Msg: "All audio downloads completed!",
	}
}