package main

import (
	"bytes"
	"flag"
	"fmt"
	"io"
	"os"

	"olexsmir.xyz/clerk/journal"
	"olexsmir.xyz/clerk/journal/printer"
)

func runFormat(args []string) {
	fs := flag.NewFlagSet("format", flag.ExitOnError)
	write := fs.Bool("w", false, "Write result back to file instead of stdout")
	diff := fs.Bool("d", false, "Display diffs instead of rewriting files")
	check := fs.Bool("check", false, "Exit code 0 if already formatted, 1 otherwise")
	fs.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: clerk format [flags] [path ...]\n")
		fs.PrintDefaults()
	}
	fs.Parse(args)

	paths := fs.Args()

	// Read from stdin if no paths given
	if len(paths) == 0 {
		src, err := io.ReadAll(os.Stdin)
		if err != nil {
			fmt.Fprintf(os.Stderr, "error reading stdin: %v\n", err)
			os.Exit(1)
		}

		pf, err := journal.NewLoader().LoadBytes("stdin", src)
		if err != nil {
			fmt.Fprintf(os.Stderr, "parse error: %v\n", err)
			os.Exit(1)
		}

		var buf bytes.Buffer
		if err := printer.Fprint(&buf, pf.Ast); err != nil {
			fmt.Fprintf(os.Stderr, "format error: %v\n", err)
			os.Exit(1)
		}

		if *check {
			if bytes.Equal(src, buf.Bytes()) {
				os.Exit(0)
			}
			os.Exit(1)
		}
		os.Stdout.Write(buf.Bytes())
		return
	}

	// Process each file
	exitCode := 0
	for _, path := range paths {
		info, err := os.Stat(path)
		if err != nil {
			fmt.Fprintf(os.Stderr, "error: %s: %v\n", path, err)
			exitCode = 1
			continue
		}
		if info.IsDir() {
			fmt.Fprintf(os.Stderr, "error: %s: can only format files, not directories\n", path)
			exitCode = 1
			continue
		}

		src, err := os.ReadFile(path)
		if err != nil {
			fmt.Fprintf(os.Stderr, "error: %s: %v\n", path, err)
			exitCode = 1
			continue
		}

		pf, err := journal.NewLoader().LoadBytes(path, src)
		if err != nil {
			fmt.Fprintf(os.Stderr, "error: %s: %v\n", path, err)
			exitCode = 1
			continue
		}

		var buf bytes.Buffer
		if err := printer.Fprint(&buf, pf.Ast); err != nil {
			fmt.Fprintf(os.Stderr, "error: %s: %v\n", path, err)
			exitCode = 1
			continue
		}

		formatted := buf.Bytes()

		if *check {
			if !bytes.Equal(src, formatted) {
				fmt.Fprintf(os.Stderr, "%s: not formatted\n", path)
				exitCode = 1
			}
			continue
		}

		if *diff {
			diffLines(path, src, formatted)
			continue
		}

		if *write {
			if err := os.WriteFile(path, formatted, 0o644); err != nil {
				fmt.Fprintf(os.Stderr, "error: %s: %v\n", path, err)
				exitCode = 1
			}
		} else {
			os.Stdout.Write(formatted)
		}
	}

	os.Exit(exitCode)
}

func diffLines(path string, src, formatted []byte) {
	// simple diff display
	if bytes.Equal(src, formatted) {
		return
	}
	fmt.Fprintf(os.Stderr, "--- %s\n+++ %s\n", path, path)
	// TODO: proper line-by-line diff
}