// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

// Command gasm is the developer frontend for GAsm — Go's Plan 9 assembler.
// It bundles a token dumper, a parser, a formatter, a linter and a language
// server into one binary.  Every subcommand works headlessly so it can be
// driven from scripts and CI as well as from an editor.
package main

import (
	"flag"
	"fmt"
	"io"
	"os"
	"strings"

	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
	"sourcedock.dev/petrbalvin/gasm-devkit/asm"
	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
	"sourcedock.dev/petrbalvin/gasm-devkit/format"
	"sourcedock.dev/petrbalvin/gasm-devkit/lexer"
	"sourcedock.dev/petrbalvin/gasm-devkit/lint"
	"sourcedock.dev/petrbalvin/gasm-devkit/lsp"
	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
)

// version is the release version, stamped at build time via
// -ldflags "-X main.version=…" (defaulting to the current release).
var version = "0.4.0"

func main() {
	if len(os.Args) < 2 {
		usage(os.Stderr)
		os.Exit(2)
	}
	switch os.Args[1] {
	case "tokens":
		os.Exit(cmdTokens(os.Args[2:]))
	case "parse":
		os.Exit(cmdParse(os.Args[2:]))
	case "fmt":
		os.Exit(cmdFmt(os.Args[2:]))
	case "lint":
		os.Exit(cmdLint(os.Args[2:]))
	case "asm":
		os.Exit(cmdAsm(os.Args[2:]))
	case "lsp":
		os.Exit(cmdLSP(os.Args[2:]))
	case "version", "--version", "-V":
		fmt.Printf("gasm %s\n", version)
	case "help", "-h", "--help":
		usage(os.Stdout)
	default:
		fmt.Fprintf(os.Stderr, "gasm: unknown command %q\n\n", os.Args[1])
		usage(os.Stderr)
		os.Exit(2)
	}
}

func usage(w io.Writer) {
	fmt.Fprintf(w, `gasm %s — developer tooling for Go's Plan 9 assembler

Usage:
  gasm tokens <file>          print the lexical token stream
  gasm parse  <file>          parse and report syntax errors
  gasm fmt    [-w] <file...>  canonicalise formatting (-w writes in place)
  gasm lint   <file...>       run static checks
  gasm asm    [-o out.bin] <file>  assemble to machine code (amd64, Phase 2)
  gasm lsp                    run the language server over stdio
  gasm version                print the version
`, version)
}

// readSource returns the contents of path, or stdin when path is "-".
func readSource(path string) (string, error) {
	if path == "-" {
		b, err := io.ReadAll(os.Stdin)
		return string(b), err
	}
	b, err := os.ReadFile(path)
	return string(b), err
}

func cmdTokens(args []string) int {
	fs := flag.NewFlagSet("tokens", flag.ExitOnError)
	fs.Parse(args)
	if fs.NArg() != 1 {
		fmt.Fprintln(os.Stderr, "usage: gasm tokens <file>")
		return 2
	}
	src, err := readSource(fs.Arg(0))
	if err != nil {
		fmt.Fprintln(os.Stderr, "gasm:", err)
		return 1
	}
	for _, tok := range lexer.Tokenize(src) {
		fmt.Printf("%s\t%s\t%q\n", tok.Pos, tok.Kind, tok.Text)
	}
	return 0
}

func cmdParse(args []string) int {
	fs := flag.NewFlagSet("parse", flag.ExitOnError)
	fs.Parse(args)
	if fs.NArg() != 1 {
		fmt.Fprintln(os.Stderr, "usage: gasm parse <file>")
		return 2
	}
	path := fs.Arg(0)
	src, err := readSource(path)
	if err != nil {
		fmt.Fprintln(os.Stderr, "gasm:", err)
		return 1
	}
	file, errs := parser.Parse(path, src)
	for _, e := range errs {
		fmt.Fprintf(os.Stderr, "%s: %v\n", path, e)
	}
	if len(errs) > 0 {
		return 1
	}
	funcs := 0
	for _, d := range file.Decls {
		if _, ok := d.(*ast.Text); ok {
			funcs++
		}
	}
	fmt.Printf("%s: OK — %d declarations, %d functions\n", path, len(file.Decls), funcs)
	return 0
}

func cmdFmt(args []string) int {
	fs := flag.NewFlagSet("fmt", flag.ExitOnError)
	write := fs.Bool("w", false, "write result to the source file")
	fs.Parse(args)
	if fs.NArg() == 0 {
		fmt.Fprintln(os.Stderr, "usage: gasm fmt [-w] <file...>")
		return 2
	}
	rc := 0
	for _, path := range fs.Args() {
		src, err := readSource(path)
		if err != nil {
			fmt.Fprintln(os.Stderr, "gasm:", err)
			rc = 1
			continue
		}
		out := format.Source(path, src)
		if *write {
			if out != src {
				if err := os.WriteFile(path, []byte(out), 0o644); err != nil {
					fmt.Fprintln(os.Stderr, "gasm:", err)
					rc = 1
				}
			}
			continue
		}
		fmt.Print(out)
	}
	return rc
}

func cmdLint(args []string) int {
	fs := flag.NewFlagSet("lint", flag.ExitOnError)
	disable := fs.String("disable", "", "comma-separated rule codes to disable")
	fs.Parse(args)
	if fs.NArg() == 0 {
		fmt.Fprintln(os.Stderr, "usage: gasm lint <file...>")
		return 2
	}
	disabled := map[string]bool{}
	for _, code := range strings.Split(*disable, ",") {
		if code = strings.TrimSpace(code); code != "" {
			disabled[code] = true
		}
	}
	hadError := false
	for _, path := range fs.Args() {
		src, err := readSource(path)
		if err != nil {
			fmt.Fprintln(os.Stderr, "gasm:", err)
			hadError = true
			continue
		}
		file, errs := parser.Parse(path, src)
		for _, e := range errs {
			fmt.Fprintf(os.Stderr, "%s: %v\n", path, e)
			hadError = true
		}
		diags := lint.File(file, lint.Config{Arch: arch.FromFilename(path), Disable: disabled})
		for _, d := range diags {
			fmt.Printf("%s:%d:%d: %s: %s [%s]\n", path, d.Pos.Line, d.Pos.Column, d.Severity, d.Message, d.Code)
			if d.Severity == lint.Error {
				hadError = true
			}
		}
	}
	if hadError {
		return 1
	}
	return 0
}

func cmdLSP(args []string) int {
	fs := flag.NewFlagSet("lsp", flag.ExitOnError)
	fs.Parse(args)
	srv := lsp.New(os.Stdin, os.Stdout)
	if err := srv.Run(); err != nil {
		fmt.Fprintln(os.Stderr, "gasm lsp:", err)
		return 1
	}
	return 0
}

func cmdAsm(args []string) int {
	fs := flag.NewFlagSet("asm", flag.ExitOnError)
	out := fs.String("o", "", "write the concatenated machine code to this file")
	fs.Parse(args)
	if fs.NArg() != 1 {
		fmt.Fprintln(os.Stderr, "usage: gasm asm [-o out.bin] <file>")
		return 2
	}
	path := fs.Arg(0)
	if arch.FromFilename(path) != arch.AMD64 {
		fmt.Fprintln(os.Stderr, "gasm asm: only amd64 is supported in this Phase 2 increment")
		return 1
	}
	src, err := readSource(path)
	if err != nil {
		fmt.Fprintln(os.Stderr, "gasm:", err)
		return 1
	}
	f, errs := parser.Parse(path, src)
	for _, e := range errs {
		fmt.Fprintf(os.Stderr, "%s: %v\n", path, e)
	}
	if len(errs) > 0 {
		return 1
	}

	img, err := asm.AssembleFile(f)
	if err != nil {
		fmt.Fprintf(os.Stderr, "%s: %v\n", path, err)
		return 1
	}
	if len(img.Funcs) == 0 {
		fmt.Fprintln(os.Stderr, "gasm asm: no assemblable TEXT functions found")
		return 1
	}
	for _, fn := range img.Funcs {
		code := img.Code[fn.Offset : fn.Offset+fn.Size]
		fmt.Printf("%s: %d bytes\n", fn.Name, fn.Size)
		for i := 0; i < len(code); i += 16 {
			end := i + 16
			if end > len(code) {
				end = len(code)
			}
			fmt.Printf("  %04x:", i)
			for _, b := range code[i:end] {
				fmt.Printf(" %02x", b)
			}
			fmt.Println()
		}
	}
	if len(img.Data) > 0 {
		fmt.Printf("data: %d bytes at 0x%x\n", len(img.Data), len(img.Code))
		for _, d := range f.Decls {
			g, ok := d.(*ast.Globl)
			if !ok || g.Name == nil || g.Name.Pseudo != "SB" {
				continue
			}
			size := 0
			if g.Size != nil && g.Size.Imm.HasVal {
				size = int(g.Size.Imm.Val)
			}
			fmt.Printf("  %s: %d bytes at 0x%x\n", g.Name.Name, size, img.Symbols[g.Name.Name])
		}
		for i := 0; i < len(img.Data); i += 16 {
			end := i + 16
			if end > len(img.Data) {
				end = len(img.Data)
			}
			fmt.Printf("  %04x:", len(img.Code)+i)
			for _, b := range img.Data[i:end] {
				fmt.Printf(" %02x", b)
			}
			fmt.Println()
		}
	}
	if *out != "" {
		all := img.Bytes()
		if err := os.WriteFile(*out, all, 0o644); err != nil {
			fmt.Fprintln(os.Stderr, "gasm asm:", err)
			return 1
		}
		fmt.Printf("wrote %d bytes to %s\n", len(all), *out)
	}
	return 0
}