package cli

import (
	"fmt"
	"os"
	"path/filepath"

	"github.com/spf13/cobra"

	"galahad2lcd/internal/config"
)

// applyOverrides merges explicitly provided flags into cfg. Zero-valued
// flags are ignored unless the user actually changed them.
func applyOverrides(cmd *cobra.Command, cfg *config.Config, input string, rotate int, speed, fps float64) error {
	if cmd.Flags().Changed("input") {
		abs, err := resolveInput(input)
		if err != nil {
			return err
		}
		cfg.Display.Input = abs
	}
	if cmd.Flags().Changed("rotate") {
		cfg.Display.Rotate = rotate
	}
	if cmd.Flags().Changed("speed") {
		cfg.Display.Speed = speed
	}
	if cmd.Flags().Changed("fps") {
		cfg.Stream.FPS = fps
	}
	return nil
}

// resolveInput converts a relative path to an absolute one and verifies the
// file exists, returning a helpful error otherwise.
func resolveInput(input string) (string, error) {
	abs, err := filepath.Abs(input)
	if err != nil {
		return "", fmt.Errorf("resolve input %q: %w", input, err)
	}
	if st, err := os.Stat(abs); err != nil {
		return "", fmt.Errorf("input file %q does not exist", abs)
	} else if st.IsDir() {
		return "", fmt.Errorf("input %q is a directory, expected a media file", abs)
	}
	return abs, nil
}