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

package asm

import (
	"testing"

	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
)

func TestArm64LDRSTREncoding(t *testing.T) {
	tests := []struct {
		name string
		got  uint32
		want uint32
	}{
		{"LDR X4, [SP, #56]", a64LSU(3, 0, 1, 7, 31, 4), 0xf9401fe4},
		{"STR X4, [SP, #64]", a64LSU(3, 0, 0, 8, 31, 4), 0xf90023e4},
		{"STR X5, [SP, #32]", a64LSU(3, 0, 0, 4, 31, 5), 0xf90013e5},
		{"LDR X6, [SP, #32]", a64LSU(3, 0, 1, 4, 31, 6), 0xf94013e6},
	}
	for _, tt := range tests {
		if tt.got != tt.want {
			t.Errorf("%s: got %08x, want %08x", tt.name, tt.got, tt.want)
		}
	}
}

func TestArm64PrologueEncoding(t *testing.T) {
	fi := arm64FrameInfo{autosize: 48, frame: 32, leaf: false}
	pro := arm64Prologue(fi)
	if len(pro) != 12 {
		t.Fatalf("prologue length: got %d, want 12", len(pro))
	}
	expected := []uint32{0xf81d0ffe, 0xf81f83fd, 0xd10023fd}
	for i, w := range leWords(pro) {
		if w != expected[i] {
			t.Errorf("prologue word %d: got %08x, want %08x", i, w, expected[i])
		}
	}
}

func TestArm64EpilogueSmallEncoding(t *testing.T) {
	fi := arm64FrameInfo{autosize: 48, frame: 32, leaf: false}
	ret := arm64Return(fi)
	if len(ret) != 12 {
		t.Fatalf("epilogue length: got %d, want 12", len(ret))
	}
	// Non-leaf small frame: LDR FP, [SP, #-8]; LDR.P LR, [SP], #48; RET
	expected := []uint32{0xf85f83fd, 0xf84307fe, 0xd65f03c0}
	for i, w := range leWords(ret) {
		if w != expected[i] {
			t.Errorf("epilogue word %d: got %08x, want %08x", i, w, expected[i])
		}
	}
}

func TestArm64LargeFrameEncoding(t *testing.T) {
	fi := arm64FrameInfo{autosize: 272, frame: 256, leaf: false}
	pro := arm64Prologue(fi)
	if len(pro) != 16 {
		t.Fatalf("prologue length: got %d, want 16", len(pro))
	}
	expected := []uint32{0xd10443f4, 0xa93ffa9d, 0x9100029f, 0xd10023fd}
	for i, w := range leWords(pro) {
		if w != expected[i] {
			t.Errorf("prologue word %d: got %08x, want %08x", i, w, expected[i])
		}
	}

	epi := arm64Return(fi)
	if len(epi) != 12 {
		t.Fatalf("epilogue length: got %d, want 12", len(epi))
	}
	eexpected := []uint32{0xa97ffbfd, 0x910443ff, 0xd65f03c0}
	for i, w := range leWords(epi) {
		if w != eexpected[i] {
			t.Errorf("epilogue word %d: got %08x, want %08x", i, w, eexpected[i])
		}
	}
}

func TestArm64NoFrame(t *testing.T) {
	fi := arm64FrameInfo{autosize: 0, frame: 0, leaf: true}
	pro := arm64Prologue(fi)
	if len(pro) != 0 {
		t.Errorf("no-frame prologue: got %d bytes, want 0", len(pro))
	}
	ret := arm64Return(fi)
	if len(ret) != 4 {
		t.Fatalf("no-frame return: got %d bytes, want 4", len(ret))
	}
	if leWord(ret) != 0xd65f03c0 {
		t.Errorf("no-frame RET: got %08x, want d65f03c0", leWord(ret))
	}
}

func TestArm64RegNum(t *testing.T) {
	tests := []struct {
		name string
		want int
	}{
		{"R0", 0}, {"R4", 4}, {"R29", 29}, {"R30", 30}, {"R31", 31},
		{"FP", 29}, {"LR", 30}, {"LINK", 30}, {"SP", 31}, {"ZR", 31},
		{"F0", 0}, {"F4", 4}, {"F31", 31},
		{"INVALID", -1}, {"X0", -1}, {"", -1},
	}
	for _, tt := range tests {
		got := arm64RegNum(tt.name)
		if got != tt.want {
			t.Errorf("arm64RegNum(%q) = %d, want %d", tt.name, got, tt.want)
		}
	}
}

func TestArm64ComputeFrame(t *testing.T) {
	src := "TEXT ·f(SB), NOSPLIT, $32-0\n\tADD\tR4, R5\n\tRET\n"
	f, errs := parser.Parse("test_arm64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	fi := arm64ComputeFrame(f.Decls[0].(*ast.Text))
	if fi.frame != 32 {
		t.Errorf("frame: got %d, want 32", fi.frame)
	}
	if fi.autosize != 48 { // 32+8=40, aligned to48
		t.Errorf("autosize: got %d, want 48", fi.autosize)
	}
	// ADD + RET with no CALL/BL → leaf
	if !fi.leaf {
		t.Error("expected leaf")
	}
}

func TestArm64IsLeaf(t *testing.T) {
	src := "TEXT ·f(SB), NOSPLIT, $0-0\n\tADD\tR4, R5\n\tRET\n"
	f, errs := parser.Parse("test_arm64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	if !arm64IsLeaf(f.Decls[0].(*ast.Text)) {
		t.Error("expected leaf")
	}

	src2 := "TEXT ·f(SB), NOSPLIT, $0-0\n\tBL\tother(SB)\n\tRET\n"
	f2, errs := parser.Parse("test_arm64.s", src2)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	if arm64IsLeaf(f2.Decls[0].(*ast.Text)) {
		t.Error("expected non-leaf")
	}
}

func TestArm64Bitmask(t *testing.T) {
	tests := []struct {
		v             uint64
		sf            int
		N, immr, imms uint32
		ok            bool
	}{
		{1, 1, 1, 0, 0, true},                     // single bit at pos 0
		{2, 1, 1, 63, 0, true},                    // single bit at pos 1 (immr = esize-1)
		{0, 1, 0, 0, 0, false},                    // zero is not a bitmask
		{0xFFFFFFFFFFFFFFFF, 1, 0, 0, 0, false},   // all ones is not a bitmask
		{0x5555555555555555, 1, 0, 0, 0x3E, true}, // alternating bits (esize=2, ones=1)
		{0xFFFFFFFF00000000, 1, 1, 32, 31, true},  // upper 32 bits set (esize=64, ones=32)
	}
	for _, tt := range tests {
		N, immr, imms, ok := arm64Bitmask(tt.v, tt.sf)
		if ok != tt.ok {
			t.Errorf("arm64Bitmask(%#x, %d): ok=%v, want %v", tt.v, tt.sf, ok, tt.ok)
			continue
		}
		if ok && (N != tt.N || immr != tt.immr || imms != tt.imms) {
			t.Errorf("arm64Bitmask(%#x, %d): N=%d immr=%d imms=%d, want N=%d immr=%d imms=%d",
				tt.v, tt.sf, N, immr, imms, tt.N, tt.immr, tt.imms)
		}
	}
}

func TestArm64AssembleFile(t *testing.T) {
	src := `#include "textflag.h"

TEXT ·simple(SB), NOSPLIT, $0-0
	MOV	R4, R5
	ADD	R4, R5, R6
	RET
`
	f, errs := parser.Parse("test_arm64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileARM64(f)
	if err != nil {
		t.Fatalf("AssembleFileARM64: %v", err)
	}
	if len(img.Funcs) != 1 {
		t.Fatalf("got %d funcs, want 1", len(img.Funcs))
	}
	fn := img.Funcs[0]
	if fn.Name != "simple" {
		t.Errorf("func name: got %q, want %q", fn.Name, "simple")
	}
	//3 instructions ×4 bytes =12
	if fn.Size != 12 {
		t.Errorf("func size: got %d, want 12", fn.Size)
	}
}

func TestArm64AssembleFileWithFrame(t *testing.T) {
	src := `#include "textflag.h"

TEXT ·framed(SB), NOSPLIT, $16-8
	MOVD	arg+0(FP), R4
	ADD	$1, R4, R4
	MOVD	R4, ret+0(FP)
	RET
`
	f, errs := parser.Parse("test_arm64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileARM64(f)
	if err != nil {
		t.Fatalf("AssembleFileARM64: %v", err)
	}
	if len(img.Funcs) != 1 {
		t.Fatalf("got %d funcs, want 1", len(img.Funcs))
	}
	fn := img.Funcs[0]
	if fn.Frame != 16 {
		t.Errorf("frame: got %d, want 16", fn.Frame)
	}
	// Prologue (3×4=12) + body (3×4=12) + RET epilogue (3×4=12) = 36
	if fn.Size != 36 {
		t.Errorf("func size: got %d, want 36", fn.Size)
	}
}

func TestArm64AssembleFileWithBranches(t *testing.T) {
	src := `#include "textflag.h"

TEXT ·branch(SB), NOSPLIT, $0-0
	BEQ	done
	BNE	skip
skip:
	ADD	R4, R5
done:
	RET
`
	f, errs := parser.Parse("test_arm64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileARM64(f)
	if err != nil {
		t.Fatalf("AssembleFileARM64: %v", err)
	}
	fn := img.Funcs[0]
	if fn.Size != 16 {
		t.Errorf("func size: got %d, want 16", fn.Size)
	}
}

func TestArm64AssembleFileWithJumpChain(t *testing.T) {
	src := `#include "textflag.h"

TEXT ·chain(SB), NOSPLIT, $0-0
	BNE	skip
	ADD	R4, R5
	RET
skip:
	B	target
target:
	ADD	R6, R7
	RET
`
	f, errs := parser.Parse("test_arm64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileARM64(f)
	if err != nil {
		t.Fatalf("AssembleFileARM64: %v", err)
	}
	// BNE should be redirected past skip→target to target directly.
	if img.Funcs[0].Size != 24 {
		t.Errorf("func size: got %d, want 24", img.Funcs[0].Size)
	}
}

func TestArm64AssembleErrors(t *testing.T) {
	tests := []struct {
		name string
		src  string
	}{
		{"unsupported", "TEXT ·f(SB), NOSPLIT, $0-0\n\tINVALID\tR4, R5\n\tRET\n"},
		{"undefined label", "TEXT ·f(SB), NOSPLIT, $0-0\n\tB\tnosuch\n\tRET\n"},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			f, errs := parser.Parse("test_arm64.s", tt.src)
			if len(errs) > 0 {
				return // parse error, that's fine
			}
			_, err := AssembleFileARM64(f)
			if err == nil {
				t.Error("expected error, got nil")
			}
		})
	}
}

func TestArm64Movcon(t *testing.T) {
	tests := []struct {
		v    int64
		want int
	}{
		{0, 0},            // 0 fits at shift 0
		{1, 0},            // single bit at shift 0
		{0x10000, 16},     // single bit at shift 16
		{0x100000000, 32}, // single bit at shift 32
		{0xFF, 0},         // 0xFF fits at shift 0
		{0x12345, -1},     // multiple chunks, not movcon
	}
	for _, tt := range tests {
		got := arm64Movcon(tt.v)
		if got != tt.want {
			t.Errorf("arm64Movcon(%#x) = %d, want %d", tt.v, got, tt.want)
		}
	}
}

func TestArm64RegClassOf(t *testing.T) {
	if arm64RegClassOf("R4") != arm64ClsGR {
		t.Error("R4 should be GR")
	}
	if arm64RegClassOf("F4") != arm64ClsFP {
		t.Error("F4 should be FP")
	}
	if arm64RegClassOf("") != arm64ClsNone {
		t.Error("empty should be None")
	}
}

func TestArm64ResolvePseudo(t *testing.T) {
	fi := arm64FrameInfo{autosize: 48, frame: 32}
	// FP: offset = sym.Offset + autosize +8
	base, off := arm64ResolvePseudo(&ast.Symbol{Pseudo: "FP", Offset: 0}, fi)
	if base != 31 || off != 56 {
		t.Errorf("FP: base=%d off=%d, want 31, 56", base, off)
	}
	// SP: offset = sym.Offset + frame +8
	base, off = arm64ResolvePseudo(&ast.Symbol{Pseudo: "SP", Offset: -8}, fi)
	if base != 31 || off != 32 {
		t.Errorf("SP: base=%d off=%d, want 31, 32", base, off)
	}
	// SB: unresolved
	base, _ = arm64ResolvePseudo(&ast.Symbol{Pseudo: "SB"}, fi)
	if base != -1 {
		t.Errorf("SB: base=%d, want -1", base)
	}
}

// leWord reads a little-endian uint32 from b.
func leWord(b []byte) uint32 {
	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
}

// leWords reads all little-endian uint32s from b.
func leWords(b []byte) []uint32 {
	n := len(b) / 4
	w := make([]uint32, n)
	for i := range w {
		w[i] = leWord(b[i*4:])
	}
	return w
}