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

package format

import (
	"slices"
	"strings"
	"testing"

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

// TestFormatPreservesMacroAdjacency pins the distinction the macro language
// draws from the source's layout: a '(' glued to a #define name makes the
// macro parameterised, while one separated by a space leaves it an object
// macro whose body happens to open with a parenthesis.  Both spellings are
// valid input and each must format to itself, because swapping one for the
// other changes what every use of the macro expands to.
func TestFormatPreservesMacroAdjacency(t *testing.T) {
	for _, in := range []string{
		"#define A(x) x+1\n",
		"#define A (x) x+1\n",
		"#define A(x) y x y\n",
		"#define A ()\n",
	} {
		if got := Source(in); got != in {
			t.Errorf("formatting %q:\n got %q", in, got)
		}
	}
}

// TestFormatPreservesExpansionSemantics proves the formatter's contract on
// the assembly path: a file the expander reads cleanly must expand to exactly
// the same statements after formatting.  Each case is a macro shape whose
// meaning lives in the source's layout, where a formatter that only counts
// tokens cannot see the difference it destroys.
func TestFormatPreservesExpansionSemantics(t *testing.T) {
	cases := []struct {
		name string
		src  string
	}{
		{
			// An object macro whose body opens with a parenthesis: gluing the
			// '(' to the name would turn it into a parameterised one, and the
			// bare use would stop expanding at all.
			name: "object macro with parenthesised body",
			src: "#define M (BX)\n" +
				"TEXT ·f(SB), $0\n" +
				"\tMOVL M, AX\n" +
				"\tRET\n",
		},
		{
			// A zero-argument macro invoked on a line whose mnemonic padding
			// opens a gap before the '(': the invocation must still expand,
			// because the parentheses are tokens however far apart.
			name: "zero-argument macro with alignment padding",
			src: "#define A() ADD $1, R0\n" +
				"TEXT ·f(SB), $0\n" +
				"\tA()\n" +
				"\tRET\n",
		},
		{
			// The arm64 style: a macro body written across continuations
			// without ';' separators.  The expansion splits the body at the
			// line boundaries, so flattening the continuations would fuse two
			// instructions into one operand list.
			name: "continuation body without semicolons",
			src: "#define M() \\\n" +
				"\tADD $1, R0 \\\n" +
				"\tSUB $2, R1\n" +
				"TEXT ·f(SB), $0\n" +
				"\tM()\n" +
				"\tRET\n",
		},
		{
			// The mixed style of the runtime sources: continuations that also
			// carry ';' separators inside some of their lines.
			name: "continuation body with semicolons",
			src: "#define PAIR(v) \\\n" +
				"\tADD $v, R0; \\\n" +
				"\tSUB $v, R1\n" +
				"TEXT ·f(SB), $0\n" +
				"\tPAIR(3)\n" +
				"\tRET\n",
		},
		{
			// A parameterised macro whose formal list itself spans a
			// continuation: the body opens on the next line, and the formal
			// list must stay glued to the name.
			name: "continuation after the formal list",
			src: "#define M(a, b) \\\n" +
				"\tADD $a, b\n" +
				"TEXT ·f(SB), $0\n" +
				"\tM(1, R0)\n" +
				"\tRET\n",
		},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			out := Source(tc.src)
			if again := Source(out); again != out {
				t.Fatalf("not idempotent:\n%s", again)
			}
			assertSameExpansion(t, tc.src, out)
		})
	}
}

// assertSameExpansion expands src and formatted with the macro machinery and
// compares the statement sequences they produce.
func assertSameExpansion(t *testing.T, src, formatted string) {
	t.Helper()
	before, errs := parser.ParseWithOptions("in.s", src, parser.Options{Expand: true})
	if len(errs) > 0 {
		t.Fatalf("source does not expand: %v", errs)
	}
	after, errs := parser.ParseWithOptions("out.s", formatted, parser.Options{Expand: true})
	if len(errs) > 0 {
		t.Fatalf("formatted source does not expand: %v\n%s", errs, formatted)
	}
	want, got := stmtSignature(before), stmtSignature(after)
	if !slices.Equal(got, want) {
		t.Fatalf("expansion changed:\n--- before ---\n%q\n--- after ---\n%q\n%s", want, got, formatted)
	}
}

// TestContinuationBodyNotFlattened pins the rendered spelling of a
// continuation body directly: the backslash boundaries the input carried are
// the canonical form, not a flattened single line.
func TestContinuationBodyNotFlattened(t *testing.T) {
	in := "#define M() \\\n\tADD $1, R0 \\\n\tSUB $2, R1\n"
	if got := Source(in); got != in {
		t.Fatalf("continuation body must render to itself:\n got %q\nwant %q", got, in)
	}
	if strings.Contains(strings.ReplaceAll(Source(in), "\\\n", ""), "ADD $1, R0 SUB") {
		t.Fatal("continuation body was flattened into one physical line")
	}
}