package interpreter

import (
	"fmt"
	"strings"
	"testing"

	"usebox.net/lang/ast"
	"usebox.net/lang/errors"
	"usebox.net/lang/parser"
	"usebox.net/lang/tokenizer"
)

func run(input string) (any, error) {
	tr := tokenizer.NewTokenizer("-", strings.NewReader(input))
	toks, err := tr.Scan()
	if err != nil {
		return nil, err
	}
	p := parser.NewParser(BuiltInTypes())
	tree, err := p.Parse(toks)
	if err != nil {
		errs := err.(errors.ErrorList)
		return nil, errs.Errors[0]
	}

	i := NewInterpreter()
	var val any
	for _, expr := range tree {
		if val, err = i.Interp(expr); err != nil {
			return nil, err
		}
	}
	return val, nil
}

func expectNumber(t *testing.T, input string, n ast.Number) {
	val, err := run(input)
	if err != nil {
		t.Errorf("Unexpected error %s (input: %s)", err, input)
	}
	i, ok := val.(ast.Number)
	if !ok {
		t.Errorf("Number expected, got %T instead (input: %s)", val, input)
	} else if i != n {
		t.Errorf("%d expected, got %d instead (input: %s)", n, i, input)
	}
}

func expectBool(t *testing.T, input string, b bool) {
	val, err := run(input)
	if err != nil {
		t.Errorf("Unexpected error %s (input: %s)", err, input)
	}
	i, ok := val.(bool)
	if !ok {
		t.Errorf("bool expected, got %T instead (input: %s)", val, input)
	} else if i != b {
		t.Errorf("%v expected, got %v instead (input: %s)", b, i, input)
	}
}

func expectString(t *testing.T, input string, s string) {
	val, err := run(input)
	if err != nil {
		t.Errorf("unexpected error %s (input: %s)", err, input)
	}
	i, ok := val.(string)
	if !ok {
		t.Errorf("string expected, got %T instead (input: %s)", val, input)
	} else if i != s {
		t.Errorf("%s expected, got %s instead (input: %s)", s, i, input)
	}
}

func expectError(t *testing.T, input string, code errors.ErrCode) {
	_, err := run(input)
	if err == nil {
		t.Errorf("expected error and didn't happen (input: %s)", input)
	}
	if e, ok := err.(errors.Error); !ok {
		t.Errorf("error not an Error (input: %s): %s", input, err)
	} else {
		if e.Code != code {
			t.Errorf("error %d expected, got %d -> %s (input: %s)", code, e.Code, e, input)
		}
	}
}

func TestNumExpr(t *testing.T) {
	expectNumber(t, "1;", 1)
	expectNumber(t, "123;", 123)
	expectNumber(t, "0x123;", 0x123)
	expectNumber(t, "0b101;", 0b101)
	expectNumber(t, "1 + 1;", 2)
	expectNumber(t, "2 + 3 * 4;", 14)
	expectNumber(t, "(5 - (3 - 1)) + -1;", 2)
}

func TestInvalidOp(t *testing.T) {
	// these operators are only valid for numbers

	expectError(t, "true + \"a\";", errors.InvalidOperation)
	expectError(t, "\"a\" + false;", errors.InvalidOperation)
	expectError(t, "\"a\" + \"a\";", errors.InvalidOperation)
	expectError(t, "-false;", errors.InvalidOperation)
	expectError(t, "-true;", errors.InvalidOperation)
	expectError(t, "~false;", errors.InvalidOperation)
	expectError(t, "~true;", errors.InvalidOperation)
	expectError(t, "-\"a\";", errors.InvalidOperation)
	expectError(t, "~\"a\";", errors.InvalidOperation)

	for _, op := range []string{
		"-", "+", "*", "/", "%", "&", "<<", ">>", "|", "^", "<", ">", "<=", ">=",
	} {
		expectError(t, fmt.Sprintf("1 %s true;", op), errors.InvalidOperation)
		expectError(t, fmt.Sprintf("true %s 1;", op), errors.InvalidOperation)
		expectError(t, fmt.Sprintf("1 %s \"a\";", op), errors.InvalidOperation)
		expectError(t, fmt.Sprintf("\"a\" %s 1;", op), errors.InvalidOperation)
	}

	// these are invalid with numbers too
	expectError(t, "1 / 0;", errors.InvalidOperation)
	expectError(t, "1 % 0;", errors.InvalidOperation)
}

func TestAssign(t *testing.T) {
	expectNumber(t, "var a number; a = 1;", 1)
	expectString(t, "var a string = \"v\"; var b string = a; b;", "v")
	expectBool(t, "var a number = 1; var b number = 2; var c number = 3; a = b = c; a == b && a== 3;", true)
	expectBool(t, "var a number; var b number = a = 1; a == b && a == 1;", true)

	// local
	expectNumber(t, `{
        var a number = 1;
        if a != 1 {
            panic("1 expected");
        }
        a = 2;
        if a != 2 {
            panic("2 expected");
        }
        println(a = 3);
        a;
    }`, 3)

	// scopes and shadowing
	expectNumber(t, `
        var a number = 1;
        if a != 1 {
            panic("1 expected");
        }
        {
            var a number = 2;
            if a != 2 {
                panic("2 expected");
            }
        }
        a;`, 1)

	expectError(t, "a = 1;", errors.UndefinedIdent)

	// syntax error; perhaps should be in the parser
	if _, err := run("var a number; (a) = 1;"); err == nil {
		t.Error("error expected by didn't happen")
	}
	if _, err := run("var a number; a + a = 1;"); err == nil {
		t.Error("error expected by didn't happen")
	}
}

func TestPrintln(t *testing.T) {
	expectNumber(t, "println();", 1)
	expectNumber(t, "println(1);", 2)
	expectNumber(t, "println(true);", 5)
	expectNumber(t, "println(\"hello\");", 6)
	expectNumber(t, "println(1, \"one\");", 5)
}

func TestEquality(t *testing.T) {
	expectBool(t, "true == true;", true)
	expectBool(t, "true == false;", false)
	expectBool(t, "false == true;", false)
	expectBool(t, "false == false;", true)

	expectBool(t, "1 == 1;", true)
	expectBool(t, "0 != 1;", true)
	expectBool(t, "\"a\" == \"a\";", true)
	expectBool(t, "\"a\" != \"b\";", true)

	expectBool(t, "true != true;", false)
	expectBool(t, "true != false;", true)
	expectBool(t, "false != true;", true)
	expectBool(t, "false != false;", false)

	expectError(t, "true == 1;", errors.TypeMismatch)
	expectError(t, "true == \"true\";", errors.TypeMismatch)
	expectError(t, "false == 0;", errors.TypeMismatch)
	expectError(t, "false == \"\";", errors.TypeMismatch)
	expectError(t, "false == \"false\";", errors.TypeMismatch)
}

func TestNot(t *testing.T) {
	expectBool(t, "!true;", false)
	expectBool(t, "!false;", true)

	expectBool(t, "!0;", true)
	expectBool(t, "!1;", false)
	expectBool(t, "!\"\";", true)
	expectBool(t, "!\"a\";", false)

	expectBool(t, "!!true;", true)
}

func TestLogical(t *testing.T) {
	expectBool(t, "true && true;", true)
	expectBool(t, "true && false;", false)
	expectBool(t, "false && true;", false)

	expectBool(t, "true || true;", true)
	expectBool(t, "true || false;", true)
	expectBool(t, "false || true;", true)

	expectBool(t, "1 == 1 && 1 != 2;", true)
	expectBool(t, "1 != 1 || 1 != 2;", true)

	expectBool(t, "1 & 1 && 0 | 1;", true)
	expectBool(t, "1 & 1 && 2 & 1;", false)
	expectBool(t, "1 & 1 || 0 | 1;", true)
	expectBool(t, "2 & 1 || 1 & 2;", false)
}

func TestIfElse(t *testing.T) {
	expectBool(t, "if 1 == 1 { true; }", true)

	val, err := run("if 1 != 1 { true; }")
	if err != nil {
		t.Errorf("unexpected error %s", err)
	}
	if val != nil {
		t.Errorf("none expected, %T found", val)
	}

	expectBool(t, "if 1 != 1 { false; } else { true; }", true)
	expectBool(t, "if 1 == 1 { false; } else { true; }", false)

	expectBool(t, "if 1 != 1 { false; } else { if 1 == 1 { true; }}", true)

	val, err = run("if 1 != 1 { true; } else { if 1 != 1 { false; }}")
	if err != nil {
		t.Errorf("unexpected error %s", err)
	}
	if val != nil {
		t.Errorf("none expected, %T found", val)
	}
}

func TestPanic(t *testing.T) {
	_, err := run("panic(\"error\");")
	if err == nil {
		t.Error("error expected and didn't happen")
	}
}

func TestFunc(t *testing.T) {
	expectString(t, `
    def wrap() func () string {
        def inFn() string {
            return "output";
        }
        return inFn;
    }
    var fn func () string = wrap();
    fn();
    `, "output")

	expectNumber(t, `
    def makeCounter() func () number {
        var i number;
        def count() number {
            i = i + 1;
            return i;
        }
        return count;
    }
    makeCounter()();
    `, 1)

	expectBool(t, `
    // why not?
    def loop(from number, to number, fn func (number)) {
        if from > to {
            return;
        }
        fn(from);
        // return is needed to trigger the tail-call optimization
        return loop(from + 1, to, fn);
    }

    def wilsonPrime(n number) bool {
        var acc number = 1;
        def fact(i number) {
            acc = (acc * i) % n;
        }
        loop(2, n - 1, fact);
        return acc == n - 1;
    }

    wilsonPrime(1789);
    `, true)

	expectNumber(t, `
    var a number = 1;
    {
      var c number;
      def add() {
          c = c + a;
          println(c, " ", a);
      }
      add(); // c is 1
      var a string;
      add(); // c is 2
      println(c);
      c;
    }
    `, 2)

	expectBool(t, `
    var a bool;
    def fn() func () {
        def inFn() {
            println("works");
            a = true;
        }
        return inFn;
    }
    fn()();
    a;`, true)

	expectBool(t, `
    var a bool;
    def fn(a bool) bool {
        return a;
    }
    fn(true);`, true)

	expectString(t, `
    def fn() { }
    {
        def fn() { }
    }
    "OK";`, "OK")

}

func TestFuncError(t *testing.T) {
	expectString(t, `
    var fn func () bool;
    "OK";`, "OK")

	expectError(t, `
    var fn func () bool;
    fn();`, errors.NotCallable)

	expectError(t, `
    def a() bool { return true; }
    var b func () number = a;
    `, errors.TypeMismatch)

	expectError(t, `
    // return with no function
    return false;
    `, errors.InvalidOperation)

	expectError(t, `
    def fn() bool { return 0; }
    fn();
    `, errors.TypeMismatch)

	expectError(t, `
    def fn() bool { }
    fn();
    `, errors.NoReturn)

	expectError(t, "true();", errors.NotCallable)
	expectError(t, "\"bad\"();", errors.NotCallable)
	expectError(t, "10();", errors.NotCallable)
	expectError(t, "true(1);", errors.NotCallable)
	expectError(t, "\"bad\"(1);", errors.NotCallable)
	expectError(t, "10(1);", errors.NotCallable)

	expectError(t, `
    var fn func() number = println;
    fn("hello");`, errors.CallError)
}

func TestFor(t *testing.T) {
	expectString(t, `
    for false {
        panic("oops");
    }
    "OK";
    `, "OK")

	// the value emited by the loops is the last
	// evaluated value inside the loop
	expectNumber(t, `
    var i number;
    for i < 10 {
        i = i + 1;
    }
    `, 10)

	expectNumber(t, `
    def mkGen() func () number {
        var n number;
        def gen() number {
            n = n + 1;
            return n;
        }
        return gen;
    }
    var c func() number = mkGen();
    var acc number;
    for c() < 10 {
        acc = acc + 1;
    }
    acc;
    `, 9)

	expectNumber(t, `
    var acc number;
    var j number;
    for j < 10 {
        var i number;
        for i < 10 {
            i = i + 1;
            acc = acc + 1;
        }
        j = j + 1;
    }
    acc;
    `, 100)

	expectError(t, `
    var a number;
    for {
        a = 1 / a;
    }
    `, errors.InvalidOperation)
}

func TestForIn(t *testing.T) {
	// the value emited by the loops is the last
	// evaluated value inside the loop
	expectNumber(t, `
    var arr [3]number = [1, 2, 10];
    for i in arr {
        i;
    }
    `, 10)

	// shadow the array variable
	expectNumber(t, `
    var a [3]number = [1, 2, 10];
    for a in a {
        println(a);
        a;
    }
    `, 10)

	expectNumber(t, `
    var acc number;
    var j [10]number;
    for i in j {
        for i in j {
            acc = acc + 1;
        }
    }
    acc;
    `, 100)
}

func TestContinue(t *testing.T) {
	expectString(t, `
    var a number;
    for a < 10 {
        a = a + 1;
        if a & 1 {
            continue;
            panic("oops");
        }
        println(a);
    }
    "OK";
    `, "OK")

	expectString(t, `
    var arr [5]number = [1, 2, 3, 4, 5];
    for a in arr {
        if a & 1 {
            continue;
            panic("oops");
        }
        println(a);
    }
    "OK";
    `, "OK")

	expectNumber(t, `
    var acc number;
    var a number;
    for a < 10 {
        var b number;
        for b < 10 {
            b = b + 1;
            if b & 1 {
                continue;
                panic("oops");
            }
            acc = acc + b;
        }
        a = a + 1;
    }
    acc;
    `, (2+4+6+8+10)*10)
}

func TestBreak(t *testing.T) {
	expectString(t, `
    for {
        break;
        panic("oops");
    }
    "OK";
    `, "OK")

	expectString(t, `
    var a [10] number;
    for i in a {
        break;
        panic("oops");
    }
    "OK";
    `, "OK")

	expectNumber(t, `
    var a number;
    for {
        if a == 20 {
            break;
        }
        a = a + 1;
        for true {
            a = a + 1;
            break;
            a = a + 1;
        }
    }
    a;
    `, 20)
}

func TestArray(t *testing.T) {
	expectError(t, "var a [0]number;", errors.InvalidLength)
	expectError(t, "var a [1]number; a[-1];", errors.InvalidIndex)
	expectError(t, "var a [1]number; a[2];", errors.InvalidIndex)
	expectError(t, "var a [1]number; a[-1] = 1;", errors.InvalidIndex)
	expectError(t, "var a [1]number; a[2] = 1;", errors.InvalidIndex)
	expectError(t, "var a [5][5]number;", errors.InvalidType)
	expectError(t, "var a number; len(a);", errors.TypeMismatch)

	expectNumber(t, `
    var arr [5]number = [1, 2, 3, 4, 5];

    var i number = 1;
    for i < len(arr) {
        arr[0] = arr[0] + arr[i];
        i = i + 1;
    }
    arr[0];
    `, 1+2+3+4+5)

	expectString(t, `
    var arr [3]string = ["one", "two", "three"];
    var arr2 [3]string;

    var i number;
    for i < len(arr) {
        arr2[i] = arr[i];
        i = i + 1;
    }
    i = 0;
    for i < len(arr) {
        if arr2[i] != arr[i] {
            panic("failed");
        }
        i = i + 1;
    }
    "OK";
    `, "OK")

	expectBool(t, `
    var a [5]bool;
    def fn(v [5]bool) {
        v[2] = true;
    }
    fn(a);
    println(a);
    a[2];
    `, true)

	expectNumber(t, `
    const a [3]number = [1, 2, 3];
    const b [3]number = [3, 2, 1];
    const c [3]number = a;
    c = b;
    c[0];
    `, 3)

	expectNumber(t, `
    var acc number;

    def a() {
        println("this is a");
        acc = acc + 10;
    }

    def b() {
        println("this is b");
        acc = acc + 10;
    }

    var arr [2]func () = [a, b];

    for i in arr {
        i();
    }
    acc;`, 20)
}

func TestErrorTag(t *testing.T) {
	expectString(t, `
    def fn() { return !?; }
    if ? fn() {
        "KO";
    }
    `, "KO")
	expectString(t, `
    def fn() { return; }
    if ? fn() {
        "KO";
    } else {
        "OK";
    }
    `, "OK")
	expectString(t, `
    def fn() number { return !? 0; }
    if ? fn() {
        "KO";
    }
    `, "KO")
	expectString(t, `
    def fn() number { return 0; }
    if !(? fn()) {
        "OK";
    }
    `, "OK")
	expectNumber(t, `
    def fn() number { return !? 99; }
    var n number;
    if ? (n = fn()) {
        n;
    }
    `, 99)
	expectString(t, `
    def fn() { return !?; }
    fn();
    // ? resets the error flag before evaluating the right side
    if ? true {
        "KO";
    } else {
        "OK";
    }
    `, "OK")
}

func TestStruct(t *testing.T) {
	expectString(t, `
    def A { var p string = "OK"; }
    var a A;
    a.p;
    `, "OK")
	expectNumber(t, `
    def A { var p number = 10; }
    var a A;
    a.p;
    `, 10)
	expectNumber(t, `
    def A { var p number; }
    var a A;
    a.p = 10;
    a.p;
    `, 10)
	expectNumber(t, `
    def A { var p number = 10; }
    var a A;
    a.p = 100;
    var b A;
    b.p;
    `, 10)
	expectNumber(t, `
    def A { var p number = 10; }
    var a [3]A;
    a[0].p + a[1].p + a[2].p;
    `, 30)
	expectNumber(t, `
    def A {
        var arr [3]number = [1, 2, 3];

        def p(index number) number {
            return arr[index];
        }
    }
    var a A;
    a.p(0) + a.p(1) + a.p(2);
    `, 6)
	expectNumber(t, `
    def A {
        var p number;
    }
    def B {
        var arr [3]A;
        var i number;

        def new() A {
            var r A = arr[i];
            r.p = i + 1;
            i = (i + 1) % 3;
            return r;
        }
    }
    var b B;
    b.new().p + b.new().p + b.new().p;
    // new should have returned a reference
    b.arr[0].p + b.arr[1].p + b.arr[2].p;
    `, 6)

	expectError(t, `
    def A {
        var a A;
    }
    `, errors.RecursiveStruct)
}