package main

import (
	"bufio"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

// runGuided is what happens when somebody double-clicks the program instead of
// typing its name at a prompt.
//
// Without this, Explorer opens a console, main() finds no arguments, prints
// the usage text to stderr and exits — and Windows destroys the window in the
// same instant. From the other side of the screen that is indistinguishable
// from a crash. So when we know we were double-clicked, we ask the one
// question the program actually needs and stay on screen until the reader is
// done.
//
// This path is entered ONLY when there are no arguments and both ends of the
// program are a real console. Any scripted or piped use takes exactly the same
// code path it always did.
//
// Guided mode runs the scan, which only reads. The repair side of PhotoRevive
// is deliberately not offered here.
func runGuided() {
	in := bufio.NewScanner(os.Stdin)

	fmt.Println()
	fmt.Println("  PhotoRevive")
	fmt.Println("  Check a photo folder for pictures that have gone bad.")
	fmt.Println()
	fmt.Println("  Point it at a folder and it opens every picture inside it, including")
	fmt.Println("  the ones in sub-folders, and tells you which ones still open cleanly,")
	fmt.Println("  which ones are damaged, and which are not really pictures at all.")
	fmt.Println()
	fmt.Println("  It only looks. Nothing is changed, moved or deleted.")
	fmt.Println()

	suggested := suggestedFolder()
	for {
		fmt.Println("  Which folder shall I check?")
		if suggested != "" {
			fmt.Printf("  (press Enter for %s)\n", suggested)
		}
		fmt.Print("  > ")

		if !in.Scan() {
			// stdin closed on us; there is nothing sensible left to ask.
			return
		}
		answer := strings.TrimSpace(in.Text())
		answer = strings.Trim(answer, `"`)
		if answer == "" {
			answer = suggested
		}
		if answer == "" {
			fmt.Println()
			fmt.Println("  I need a folder to check. Try again, or close this window.")
			fmt.Println()
			continue
		}

		info, err := os.Stat(answer)
		switch {
		case err != nil:
			fmt.Println()
			fmt.Printf("  I cannot find %q.\n", answer)
			fmt.Println("  Tip: you can drag a folder from Explorer onto this window to")
			fmt.Println("  paste its location, then press Enter.")
			fmt.Println()
			continue
		case !info.IsDir():
			fmt.Println()
			fmt.Printf("  %q is a file, not a folder. Give me the folder it sits in.\n", answer)
			fmt.Println()
			continue
		}

		fmt.Println()
		fmt.Println("  Working. Every picture has to be opened, so a big library can take")
		fmt.Println("  a few minutes.")
		fmt.Println()
		runScan([]string{answer})
		break
	}

	fmt.Println()
	fmt.Println("  Done. Run it again any time on another folder.")
	fmt.Println("  There is a command-line version too, which can also try to rescue")
	fmt.Println("  damaged JPEGs into a separate folder: photorevive help")
	pause(in)
}

// suggestedFolder offers somewhere worth checking that is certain to exist, so
// the reader can get a useful answer by pressing one key.
func suggestedFolder() string {
	home, err := os.UserHomeDir()
	if err != nil {
		return ""
	}
	// The folder full of photographs is the one worth checking first.
	for _, name := range []string{"Pictures", "Downloads"} {
		candidate := filepath.Join(home, name)
		if info, err := os.Stat(candidate); err == nil && info.IsDir() {
			return candidate
		}
	}
	return home
}

// pause keeps the console window open. Explorer closes it the moment the
// process exits, so without this the reader never sees the output.
func pause(in *bufio.Scanner) {
	fmt.Println()
	fmt.Print("  Press Enter to close this window. ")
	in.Scan()
}