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.
func runGuided() {
	in := bufio.NewScanner(os.Stdin)

	fmt.Println()
	fmt.Println("  SpaceMedic")
	fmt.Println("  Find out what KIND of thing is filling up your disk.")
	fmt.Println()
	fmt.Println("  Point it at a folder and it sorts everything inside into groups —")
	fmt.Println("  temporary files, log files, cache folders, old installers, forgotten")
	fmt.Println("  downloads and big videos — then tells you how much room each group")
	fmt.Println("  takes and which files in it are the largest.")
	fmt.Println()
	fmt.Println("  It only reads. Nothing is deleted, moved or changed.")
	fmt.Println()

	suggested := suggestedFolder()
	for {
		fmt.Println("  Which folder shall I look at?")
		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 look at. 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. On a large folder this can take a minute.")
		fmt.Println()
		cmdReport([]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: spacemedic help")
	pause(in)
}

// suggestedFolder offers somewhere worth looking 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 ""
	}
	// A home directory is the honest default, but the folders that collect
	// stale installers and forgotten files are the ones worth offering first.
	for _, name := range []string{"Downloads", "Documents"} {
		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()
}