package commands

import (
	"strings"
	"testing"

	"c65gm/internal/compiler"
	"c65gm/internal/preproc"
)

func TestSubtractCommand_WillHandle(t *testing.T) {
	cmd := &SubtractCommand{}

	tests := []struct {
		name string
		line string
		want bool
	}{
		{"old syntax SUBTRACT FROM/GIVING", "SUBTRACT a FROM b GIVING c", true},
		{"old syntax SUBT FROM/arrow", "SUBT a FROM b -> c", true},
		{"old syntax SUBT minus/arrow", "SUBT a - b -> c", true},
		{"old syntax SUBTRACT minus/GIVING", "SUBTRACT a - b GIVING c", true},
		{"new syntax", "result = x - y", true},
		{"not SUBTRACT", "ADD a TO b GIVING c", false},
		{"wrong param count", "SUBTRACT a b c", false},
		{"empty", "", false},
		{"new syntax wrong op", "result = x + y", false},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			line := preproc.Line{Text: tt.line, Kind: preproc.Source}
			got := cmd.WillHandle(line)
			if got != tt.want {
				t.Errorf("WillHandle() = %v, want %v", got, tt.want)
			}
		})
	}
}

func TestSubtractCommand_OldSyntax_FROM(t *testing.T) {
	tests := []struct {
		name      string
		line      string
		setupVars func(*compiler.SymbolTable)
		wantAsm   []string
		wantErr   bool
	}{
		{
			name: "SUBTRACT a FROM b (means b-a)",
			line: "SUBTRACT 5 FROM 10 GIVING result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tlda #$05",
				"\tsta result",
			},
		},
		{
			name: "SUBTRACT byte FROM byte -> byte (variables)",
			line: "SUBTRACT a FROM b GIVING result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 10)
				st.AddVar("b", "", compiler.KindByte, 20)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda b",
				"\tsbc a",
				"\tsta result",
			},
		},
		{
			name: "SUBT a FROM b -> c with arrow",
			line: "SUBT a FROM b -> result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 10)
				st.AddVar("b", "", compiler.KindByte, 20)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda b",
				"\tsbc a",
				"\tsta result",
			},
		},
		{
			name: "SUBTRACT literal FROM variable",
			line: "SUBTRACT 10 FROM a GIVING result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 20)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda a",
				"\tsbc #$0a",
				"\tsta result",
			},
		},
		{
			name: "word FROM word -> word",
			line: "SUBTRACT x FROM y GIVING result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("x", "", compiler.KindWord, 0x1000)
				st.AddVar("y", "", compiler.KindWord, 0x2000)
				st.AddVar("result", "", compiler.KindWord, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda y",
				"\tsbc x",
				"\tsta result",
				"\tlda y+1",
				"\tsbc x+1",
				"\tsta result+1",
			},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			ctx := compiler.NewCompilerContext(&preproc.Pragma{})
			tt.setupVars(ctx.SymbolTable)

			cmd := &SubtractCommand{}
			line := preproc.Line{Text: tt.line, Kind: preproc.Source}

			err := cmd.Interpret(line, ctx)
			if tt.wantErr {
				if err == nil {
					t.Error("expected error, got nil")
				}
				return
			}
			if err != nil {
				t.Fatalf("Interpret() error = %v", err)
			}

			asm, err := cmd.Generate(ctx)
			if err != nil {
				t.Fatalf("Generate() error = %v", err)
			}

			if !equalAsmSubtr(asm, tt.wantAsm) {
				t.Errorf("Generate() mismatch\ngot:\n%s\nwant:\n%s",
					strings.Join(asm, "\n"),
					strings.Join(tt.wantAsm, "\n"))
			}
		})
	}
}

func TestSubtractCommand_OldSyntax_Minus(t *testing.T) {
	tests := []struct {
		name      string
		line      string
		setupVars func(*compiler.SymbolTable)
		wantAsm   []string
		wantErr   bool
	}{
		{
			name: "SUBT a - b (means a-b, no swap)",
			line: "SUBT 10 - 5 GIVING result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tlda #$05",
				"\tsta result",
			},
		},
		{
			name: "SUBT byte - byte -> byte (variables)",
			line: "SUBT a - b -> result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 20)
				st.AddVar("b", "", compiler.KindByte, 10)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda a",
				"\tsbc b",
				"\tsta result",
			},
		},
		{
			name: "SUBTRACT a - b GIVING c",
			line: "SUBTRACT a - b GIVING result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 20)
				st.AddVar("b", "", compiler.KindByte, 10)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda a",
				"\tsbc b",
				"\tsta result",
			},
		},
		{
			name: "SUBT variable - literal",
			line: "SUBT a - 10 -> result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 20)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda a",
				"\tsbc #$0a",
				"\tsta result",
			},
		},
		{
			name: "word - word -> word",
			line: "SUBT x - y -> result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("x", "", compiler.KindWord, 0x2000)
				st.AddVar("y", "", compiler.KindWord, 0x1000)
				st.AddVar("result", "", compiler.KindWord, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda x",
				"\tsbc y",
				"\tsta result",
				"\tlda x+1",
				"\tsbc y+1",
				"\tsta result+1",
			},
		},
		{
			name: "byte - byte -> word",
			line: "SUBT a - b GIVING result",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 20)
				st.AddVar("b", "", compiler.KindByte, 10)
				st.AddVar("result", "", compiler.KindWord, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda a",
				"\tsbc b",
				"\tsta result",
				"\tlda #0",
				"\tsbc #0",
				"\tsta result+1",
			},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			ctx := compiler.NewCompilerContext(&preproc.Pragma{})
			tt.setupVars(ctx.SymbolTable)

			cmd := &SubtractCommand{}
			line := preproc.Line{Text: tt.line, Kind: preproc.Source}

			err := cmd.Interpret(line, ctx)
			if tt.wantErr {
				if err == nil {
					t.Error("expected error, got nil")
				}
				return
			}
			if err != nil {
				t.Fatalf("Interpret() error = %v", err)
			}

			asm, err := cmd.Generate(ctx)
			if err != nil {
				t.Fatalf("Generate() error = %v", err)
			}

			if !equalAsmSubtr(asm, tt.wantAsm) {
				t.Errorf("Generate() mismatch\ngot:\n%s\nwant:\n%s",
					strings.Join(asm, "\n"),
					strings.Join(tt.wantAsm, "\n"))
			}
		})
	}
}

func TestSubtractCommand_NewSyntax(t *testing.T) {
	tests := []struct {
		name      string
		line      string
		setupVars func(*compiler.SymbolTable)
		wantAsm   []string
		wantErr   bool
	}{
		{
			name: "byte - byte -> byte",
			line: "result = a - b",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 20)
				st.AddVar("b", "", compiler.KindByte, 10)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda a",
				"\tsbc b",
				"\tsta result",
			},
		},
		{
			name: "byte - byte -> word",
			line: "result = a - b",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 20)
				st.AddVar("b", "", compiler.KindByte, 10)
				st.AddVar("result", "", compiler.KindWord, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda a",
				"\tsbc b",
				"\tsta result",
				"\tlda #0",
				"\tsbc #0",
				"\tsta result+1",
			},
		},
		{
			name: "word - word -> word",
			line: "result = x - y",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("x", "", compiler.KindWord, 0x2000)
				st.AddVar("y", "", compiler.KindWord, 0x1000)
				st.AddVar("result", "", compiler.KindWord, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda x",
				"\tsbc y",
				"\tsta result",
				"\tlda x+1",
				"\tsbc y+1",
				"\tsta result+1",
			},
		},
		{
			name: "variable - literal",
			line: "result = a - 10",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 20)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda a",
				"\tsbc #$0a",
				"\tsta result",
			},
		},
		{
			name: "literal - variable",
			line: "result = 20 - b",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("b", "", compiler.KindByte, 10)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda #$14",
				"\tsbc b",
				"\tsta result",
			},
		},
		{
			name: "constant folding",
			line: "result = 100 - 25",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tlda #$4b",
				"\tsta result",
			},
		},
		{
			name: "constant folding word",
			line: "result = $2000 - $1000",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("result", "", compiler.KindWord, 0)
			},
			wantAsm: []string{
				"\tlda #$00",
				"\tsta result",
				"\tlda #$10",
				"\tsta result+1",
			},
		},
		{
			name: "using constant in expression",
			line: "result = a - OFFSET",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 100)
				st.AddConst("OFFSET", "", compiler.KindByte, 10)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda a",
				"\tsbc #$0a",
				"\tsta result",
			},
		},
		{
			name: "word - byte -> word",
			line: "result = wval - bval",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("wval", "", compiler.KindWord, 0x1234)
				st.AddVar("bval", "", compiler.KindByte, 0x10)
				st.AddVar("result", "", compiler.KindWord, 0)
			},
			wantAsm: []string{
				"\tsec",
				"\tlda wval",
				"\tsbc bval",
				"\tsta result",
				"\tlda wval+1",
				"\tsbc #0",
				"\tsta result+1",
			},
		},
		{
			name: "error: unknown destination",
			line: "unknown = a - b",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 0)
				st.AddVar("b", "", compiler.KindByte, 0)
			},
			wantErr: true,
		},
		{
			name: "error: wrong operator",
			line: "result = a + b",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 0)
				st.AddVar("b", "", compiler.KindByte, 0)
				st.AddVar("result", "", compiler.KindByte, 0)
			},
			wantErr: true,
		},
		{
			name: "error: cannot assign to constant",
			line: "MAXVAL = a - b",
			setupVars: func(st *compiler.SymbolTable) {
				st.AddVar("a", "", compiler.KindByte, 0)
				st.AddVar("b", "", compiler.KindByte, 0)
				st.AddConst("MAXVAL", "", compiler.KindByte, 255)
			},
			wantErr: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			ctx := compiler.NewCompilerContext(&preproc.Pragma{})
			tt.setupVars(ctx.SymbolTable)

			cmd := &SubtractCommand{}
			line := preproc.Line{Text: tt.line, Kind: preproc.Source}

			err := cmd.Interpret(line, ctx)
			if tt.wantErr {
				if err == nil {
					t.Error("expected error, got nil")
				}
				return
			}
			if err != nil {
				t.Fatalf("Interpret() error = %v", err)
			}

			asm, err := cmd.Generate(ctx)
			if err != nil {
				t.Fatalf("Generate() error = %v", err)
			}

			if !equalAsmSubtr(asm, tt.wantAsm) {
				t.Errorf("Generate() mismatch\ngot:\n%s\nwant:\n%s",
					strings.Join(asm, "\n"),
					strings.Join(tt.wantAsm, "\n"))
			}
		})
	}
}

// equalAsmSubtr compares two assembly slices for equality
func equalAsmSubtr(a, b []string) bool {
	if len(a) != len(b) {
		return false
	}
	for i := range a {
		if a[i] != b[i] {
			return false
		}
	}
	return true
}