package server

import (
	"bytes"
	"context"
	"crypto/md5"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"os"
	"path/filepath"
	"slices"

	"git.lastassault.de/speatzle/morffix/constants"
	"github.com/jackc/pgx/v5"
)

var videoFileExtensions = []string{".mkv", ".mp4", ".webm", ".flv", ".avi"}

func handleScan(w http.ResponseWriter, r *http.Request) {
	if r.Method == "GET" {
		scanStatus(w, r)
		return
	}

	id := r.PathValue("id")
	if id == "" {
		http.Error(w, "No ID Set", http.StatusBadRequest)
		return
	}

	full := r.FormValue("full") == "on"

	var name string
	var path string
	var enabled bool
	err := db.QueryRow(r.Context(), "SELECT name, path, enable FROM libraries WHERE id = $1", id).Scan(&name, &path, &enabled)
	if err != nil {
		slog.ErrorContext(r.Context(), "Get Library", "err", err)
		http.Error(w, "Error Get Library: "+err.Error(), http.StatusInternalServerError)
		return
	}

	scanCtx := context.Background()
	go scan(scanCtx, id, full)

	message := "Scan Started"

	buf := bytes.Buffer{}
	err = templates.ExecuteTemplate(&buf, constants.MESSAGE_TEMPLATE_NAME, message)
	if err != nil {
		slog.ErrorContext(r.Context(), "Executing Library Template", "err", err)
		http.Error(w, "Error Executing Template: "+err.Error(), http.StatusInternalServerError)
		return
	}

	_, err = w.Write(buf.Bytes())
	if err != nil {
		slog.ErrorContext(r.Context(), "Writing http Response", "err", err)
	}
}

func scanStatus(w http.ResponseWriter, r *http.Request) {
	message := "TODO"

	buf := bytes.Buffer{}
	err := templates.ExecuteTemplate(&buf, constants.MESSAGE_TEMPLATE_NAME, message)
	if err != nil {
		slog.ErrorContext(r.Context(), "Executing Library Template", "err", err)
		http.Error(w, "Error Executing Template: "+err.Error(), http.StatusInternalServerError)
		return
	}

	_, err = w.Write(buf.Bytes())
	if err != nil {
		slog.ErrorContext(r.Context(), "Writing http Response", "err", err)
	}
}

func scan(ctx context.Context, id string, full bool) {
	slog.InfoContext(ctx, "Starting Scan", "id", id)

	// TODO Scan settings:
	// - Auto Queue Healthcheck for Changed Files
	// - Auto Queue Healthcheck for New Files
	// - Auto Queue Transcode for New Files
	// - Auto Queue Transcode for Changed Files (? Instead have library setting to queue transcode for changed files on healthcheck success)
	// - Auto Queue Health/Transcode for Unkown Status ? (might result in requeue loop)
	// - Schedule Scans Periodically
	// - Add File Monitoring for Setting Changed status and triggering tasks

	var name string
	var lpath string
	var enabled bool
	err := db.QueryRow(ctx, "SELECT name, path, enable FROM libraries WHERE id = $1", id).Scan(&name, &lpath, &enabled)
	if err != nil {
		slog.ErrorContext(ctx, "Get Library", "err", err)
		return
	}

	if !enabled {
		slog.ErrorContext(ctx, "Scan Aborted, Library not Enabled", "id", id)
		return
	}

	dirInfo, err := os.Stat(lpath)
	if err != nil {
		slog.ErrorContext(ctx, "Stating Library Path", "id", id, "path", lpath, "err", err)
		return
	}

	if !dirInfo.IsDir() {
		slog.ErrorContext(ctx, "Library Path is not a Folder", "id", id, "path", lpath)
		return
	}

	tx, err := db.Begin(ctx)
	if err != nil {
		slog.ErrorContext(ctx, "Begin Transaction", "err", err)
		return
	}
	defer tx.Rollback(ctx)

	slog.InfoContext(ctx, "Checking Files...", "id", id, "path", lpath)

	// Mark all Files as Missing
	_, err = tx.Exec(ctx, "UPDATE files SET status = $2 where library_id = $1", id, constants.FILE_STATUS_MISSING)
	if err != nil {
		slog.ErrorContext(ctx, "Setting Missing Status", "err", err)
		return
	}

	err = filepath.Walk(lpath,
		func(fullPath string, info os.FileInfo, err error) error {
			if errors.Is(err, os.ErrPermission) {
				slog.WarnContext(ctx, "Permission Denied While Scanning File", "path", fullPath)
				return nil
			} else if err != nil {
				return err
			}

			if info.IsDir() {
				// We don't care about folders
				return nil
			}

			if !slices.Contains(videoFileExtensions, filepath.Ext(fullPath)) {
				slog.InfoContext(ctx, "Skipping non video file", "path", fullPath)
				return nil
			}
			slog.InfoContext(ctx, "Hashing File", "path", fullPath, "size", info.Size())

			file, err := os.Open(fullPath)
			if err != nil {
				return fmt.Errorf("Opening File: %w", err)
			}

			hash := md5.New()
			if _, err := io.Copy(hash, file); err != nil {
				return fmt.Errorf("Reading File: %w", err)
			}
			newMD5 := hash.Sum(nil)

			slog.InfoContext(ctx, "File MD5", "path", fullPath, "size", info.Size(), "md5", newMD5)

			fPath, err := filepath.Rel(lpath, fullPath)
			if err != nil {
				return fmt.Errorf("Getting Relative Path: %w", err)
			}

			var fileID int
			var oldMD5 []byte
			var health constants.FileHealth
			err = tx.QueryRow(ctx, "SELECT id, md5, health FROM files WHERE library_id = $1 AND path = $2", id, fPath).Scan(&fileID, &oldMD5, &health)
			if errors.Is(err, pgx.ErrNoRows) {
				// File Does not Exist Yet

				slog.InfoContext(ctx, "File is New", "path", fullPath)
				_, err = tx.Exec(ctx, "INSERT INTO files (library_id, path, size, status, health, md5) VALUES ($1, $2, $3, $4, $5, $6)", id, fPath, info.Size(), constants.FILE_STATUS_EXISTS, constants.FILE_HEALTH_UNKNOWN, newMD5)
				if err != nil {
					return fmt.Errorf("Add New File to DB: %w", err)
				}
				return nil
			} else if err != nil {
				return fmt.Errorf("Getting File: %w", err)
			}

			if slices.Compare[[]byte](newMD5, oldMD5) != 0 {
				// File has changed on disk so reset health
				health = constants.FILE_HEALTH_UNKNOWN
			}
			// File Exists so update Size, status and hash
			_, err = tx.Exec(ctx, "UPDATE files SET size = $2, status = $3, health = $4, md5 = $5 WHERE id = $1", fileID, info.Size(), constants.FILE_STATUS_EXISTS, health, newMD5)
			if err != nil {
				return fmt.Errorf("Updating File in DB: %w", err)
			}
			return nil
		})
	if err != nil {
		slog.ErrorContext(ctx, "Error Walking Library", "err", err)
		return
	}

	err = tx.Commit(ctx)
	if err != nil {
		slog.ErrorContext(ctx, "Error Committing Changes", "err", err)
		return
	}

	// TODO, create health and transcode tasks if requested
	slog.InfoContext(ctx, "Scan Done", "id", id)
}