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

package asm

import (
	"os"
	"path/filepath"
	"strings"
	"testing"

	"sourcedock.dev/petrbalvin/gasm-sdk/parser"
)

// arm64AcceptedErrorShapes lists the toolchain's arm64error.s spellings gasm
// still accepts, each an acceptance superset with a known shape.  The list
// only shrinks: every tightening of the encoder moves spellings out of it,
// and a spelling reappearing here means a regression.  The catalogue is
// empty as of Go 1.27: every line the toolchain's corpus rejects, gasm
// rejects too.
var arm64AcceptedErrorShapes = []string{}

// TestArm64ToolchainErrorParity walks the toolchain's arm64error.s (Go
// 1.27, arm64) and requires gasm to reject every case the toolchain rejects.
// A live Go toolchain is needed for the source file; the test skips without
// one or in -short.
func TestArm64ToolchainErrorParity(t *testing.T) {
	if testing.Short() {
		t.Skip("live arm64error.s corpus: skipped in -short mode")
	}
	goroot := os.Getenv("GOROOT")
	if goroot == "" {
		t.Skip("no GOROOT")
	}
	path := filepath.Join(goroot, "src", "cmd", "asm", "internal", "asm", "testdata", "arm64error.s")
	data, err := os.ReadFile(path)
	if err != nil {
		t.Skip(err)
	}
	allowed := map[string]bool{}
	for _, s := range arm64AcceptedErrorShapes {
		allowed[s] = true
	}
	for raw := range strings.SplitSeq(string(data), "\n") {
		line := strings.TrimSpace(raw)
		if line == "" || strings.HasPrefix(line, "//") || strings.HasPrefix(line, "TEXT") || !strings.Contains(line, "ERROR") {
			continue
		}
		body := line
		if i := strings.Index(body, "//"); i >= 0 {
			body = strings.TrimSpace(body[:i])
		}
		body = strings.ReplaceAll(body, "\t", " ")
		body = strings.Join(strings.Fields(body), " ")
		src := "#include \"textflag.h\"\n\nTEXT ·f(SB), NOSPLIT, $0-0\n\t" + body + "\n\tRET\n"
		f, perr := parser.Parse("errorparity.s", src)
		if len(perr) > 0 {
			continue // the parser already rejects the spelling
		}
		if _, aerr := AssembleFileARM64(f); aerr == nil && !allowed[body] {
			t.Errorf("gasm accepts what the toolchain rejects: %s", body)
		}
	}
}