// Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
// All rights reserved.

// Comparison and logical operations for the Five runtime.
// Implements Harbour-compatible comparison semantics including:
//   - NIL == NIL → true, NIL == anything → false
//   - Numeric cross-type comparison (Int/Long/Double auto-promotion)
//   - String comparison respecting SET EXACT
//   - Date/Timestamp comparison
//   - Logical XOR equality (Clipper quirk)
//
// Operator hierarchy inspired by tsgo's isEqualityOperator/isRelationalOperatorOrHigher
// pattern (ref/typescript-go/internal/checker/utilities.go:772).
//
// See docs/harbour-type-system-analysis.md Section 6 for full rules.
package hbrt

import "strings"

// --- Equality operators ---

// Equal pops two values, pushes boolean result.
// Harbour: hb_vmEqual (hvm.c:3974)
func (t *Thread) Equal() {
	if t.tryBinaryOp(OpEqual) {
		return
	}
	t.sp -= 2
	a := t.stack[t.sp]
	b := t.stack[t.sp+1]
	t.stack[t.sp+1] = cachedNil
	// Fast path: Int == Int
	if a.Type() == tInt && b.Type() == tInt {
		if int64(a.scalar) == int64(b.scalar) {
			t.stack[t.sp] = cachedTrue
		} else {
			t.stack[t.sp] = cachedFalse
		}
		t.sp++
		return
	}
	if valueEqual(a, b) {
		t.stack[t.sp] = cachedTrue
	} else {
		t.stack[t.sp] = cachedFalse
	}
	t.sp++
}

// ExactEqual pops two values, pushes boolean result.
// Harbour: hb_vmExactlyEqual — arrays cannot override.
func (t *Thread) ExactEqual() {
	b := t.pop()
	a := t.pop()
	t.push(MakeBool(valueExactEqual(a, b)))
}

// NotEqual pops two values, pushes boolean result.
func (t *Thread) NotEqual() {
	if t.tryBinaryOp(OpNotEqual) {
		return
	}
	t.sp -= 2
	a := t.stack[t.sp]
	b := t.stack[t.sp+1]
	t.stack[t.sp+1] = cachedNil
	if a.Type() == tInt && b.Type() == tInt {
		if int64(a.scalar) != int64(b.scalar) {
			t.stack[t.sp] = cachedTrue
		} else {
			t.stack[t.sp] = cachedFalse
		}
		t.sp++
		return
	}
	if !valueEqual(a, b) {
		t.stack[t.sp] = cachedTrue
	} else {
		t.stack[t.sp] = cachedFalse
	}
	t.sp++
}

// --- Relational operators ---

// Less pops two values, pushes boolean result.
// Harbour: hb_vmLess (hvm.c:4176)
func (t *Thread) Less() {
	if t.tryBinaryOp(OpLess) {
		return
	}
	t.sp -= 2
	a := t.stack[t.sp]
	b := t.stack[t.sp+1]
	t.stack[t.sp+1] = cachedNil
	if a.Type() == tInt && b.Type() == tInt {
		if int64(a.scalar) < int64(b.scalar) {
			t.stack[t.sp] = cachedTrue
		} else {
			t.stack[t.sp] = cachedFalse
		}
		t.sp++
		return
	}
	cmp, ok := valueCompare(a, b)
	if !ok {
		panic(t.argError("<", a, b))
	}
	if cmp < 0 {
		t.stack[t.sp] = cachedTrue
	} else {
		t.stack[t.sp] = cachedFalse
	}
	t.sp++
}

// LessEqual pops two values, pushes boolean result.
func (t *Thread) LessEqual() {
	if t.tryBinaryOp(OpLessEqual) {
		return
	}
	t.sp -= 2
	a := t.stack[t.sp]
	b := t.stack[t.sp+1]
	t.stack[t.sp+1] = cachedNil
	// Fast path: Int <= Int (most common in FOR loops)
	if a.Type() == tInt && b.Type() == tInt {
		if int64(a.scalar) <= int64(b.scalar) {
			t.stack[t.sp] = cachedTrue
		} else {
			t.stack[t.sp] = cachedFalse
		}
		t.sp++
		return
	}
	cmp, ok := valueCompare(a, b)
	if !ok {
		panic(t.argError("<=", a, b))
	}
	if cmp <= 0 {
		t.stack[t.sp] = cachedTrue
	} else {
		t.stack[t.sp] = cachedFalse
	}
	t.sp++
}

// Greater pops two values, pushes boolean result.
func (t *Thread) Greater() {
	if t.tryBinaryOp(OpGreater) {
		return
	}
	t.sp -= 2
	a := t.stack[t.sp]
	b := t.stack[t.sp+1]
	t.stack[t.sp+1] = cachedNil
	if a.Type() == tInt && b.Type() == tInt {
		if int64(a.scalar) > int64(b.scalar) {
			t.stack[t.sp] = cachedTrue
		} else {
			t.stack[t.sp] = cachedFalse
		}
		t.sp++
		return
	}
	cmp, ok := valueCompare(a, b)
	if !ok {
		panic(t.argError(">", a, b))
	}
	if cmp > 0 {
		t.stack[t.sp] = cachedTrue
	} else {
		t.stack[t.sp] = cachedFalse
	}
	t.sp++
}

// GreaterEqual pops two values, pushes boolean result.
func (t *Thread) GreaterEqual() {
	if t.tryBinaryOp(OpGreaterEqual) {
		return
	}
	t.sp -= 2
	a := t.stack[t.sp]
	b := t.stack[t.sp+1]
	t.stack[t.sp+1] = cachedNil
	if a.Type() == tInt && b.Type() == tInt {
		if int64(a.scalar) >= int64(b.scalar) {
			t.stack[t.sp] = cachedTrue
		} else {
			t.stack[t.sp] = cachedFalse
		}
		t.sp++
		return
	}
	cmp, ok := valueCompare(a, b)
	if !ok {
		panic(t.argError(">=", a, b))
	}
	if cmp >= 0 {
		t.stack[t.sp] = cachedTrue
	} else {
		t.stack[t.sp] = cachedFalse
	}
	t.sp++
}

// --- Logical operators ---

// Not negates the boolean value on top of stack.
func (t *Thread) Not() {
	t.sp--
	a := t.stack[t.sp]
	// Fast path: logical not (most common — DO WHILE !EOF())
	if a.Type() == tLogical {
		if a.scalar != 0 {
			t.stack[t.sp] = cachedFalse
		} else {
			t.stack[t.sp] = cachedTrue
		}
		t.sp++
		return
	}
	panic(t.argError(".NOT.", a))
}

// And pops two values, pushes logical AND.
// Harbour evaluates both sides (no short-circuit in VM ops).
func (t *Thread) And() {
	t.sp -= 2
	a := t.stack[t.sp]
	b := t.stack[t.sp+1]
	t.stack[t.sp+1] = cachedNil
	if a.Type() == tLogical && b.Type() == tLogical {
		if a.scalar != 0 && b.scalar != 0 {
			t.stack[t.sp] = cachedTrue
		} else {
			t.stack[t.sp] = cachedFalse
		}
		t.sp++
		return
	}
	panic(t.argError(".AND.", a, b))
}

// Or pops two values, pushes logical OR.
func (t *Thread) Or() {
	t.sp -= 2
	a := t.stack[t.sp]
	b := t.stack[t.sp+1]
	t.stack[t.sp+1] = cachedNil
	if a.Type() == tLogical && b.Type() == tLogical {
		if a.scalar != 0 || b.scalar != 0 {
			t.stack[t.sp] = cachedTrue
		} else {
			t.stack[t.sp] = cachedFalse
		}
		t.sp++
		return
	}
	panic(t.argError(".OR.", a, b))
}

// InString implements the $ operator: "bc" $ "abcde" → .T.
func (t *Thread) InString() {
	b := t.pop()
	a := t.pop()
	if a.IsString() && b.IsString() {
		t.push(MakeBool(strings.Contains(b.AsString(), a.AsString())))
	} else {
		panic(t.argError("$", a, b))
	}
}

// PopLogical pops the top of stack and returns it as bool.
// Used by generated code for IF/WHILE conditions.
// Harbour: hb_xvmPopLogical
func (t *Thread) PopLogical() bool {
	t.sp--
	v := t.stack[t.sp]
	t.stack[t.sp] = cachedNil
	// Fast path: check type tag directly (avoid method call overhead)
	if v.Type() == tLogical {
		return v.scalar != 0
	}
	// NIL → false (Harbour treats NIL as .F. in conditions)
	if v.Type() == tNil {
		return false
	}
	panic(t.argError("logical", v))
}

// --- Fused opcodes: combined stack operations for hot loops ---
// Eliminates 3-4 function calls per FOR iteration.

// LocalLessEqualInt: t.Local(idx) <= val (no stack ops). Byref-aware.
func (t *Thread) LocalLessEqualInt(localIdx, val int) bool {
	v := t.locals[t.curFrame.localBase+localIdx-1]
	if v.Type() == tByref {
		v = (*HbRefCell)(v.ptr).V
	}
	if v.Type() == tInt {
		return int64(v.scalar) <= int64(val)
	}
	if v.Type() == tDouble {
		return v.AsNumDouble() <= float64(val)
	}
	return false
}

// LocalGreaterEqualInt: t.Local(idx) >= val (for descending FOR). Byref-aware.
func (t *Thread) LocalGreaterEqualInt(localIdx, val int) bool {
	v := t.locals[t.curFrame.localBase+localIdx-1]
	if v.Type() == tByref {
		v = (*HbRefCell)(v.ptr).V
	}
	if v.Type() == tInt {
		return int64(v.scalar) >= int64(val)
	}
	if v.Type() == tDouble {
		return v.AsNumDouble() >= float64(val)
	}
	return false
}

// --- Optimized comparison (used by generated code) ---

// EqualIntIs compares stack top with an integer constant, returns bool.
// Harbour: hb_xvmEqualIntIs (fused PUSHINT + EQUAL)
func (t *Thread) EqualIntIs(n int64) bool {
	a := t.pop()
	if a.IsNumInt() {
		return a.AsNumInt() == n
	}
	if a.IsDouble() {
		return a.AsDouble() == float64(n)
	}
	return false
}

// --- Internal comparison functions ---

// valueEqual implements Harbour's equality semantics.
// NIL == NIL → true; NIL == anything → false
// Numeric: cross-type double comparison
// String: case-sensitive (SET EXACT ON assumed for now)
// Logical: XOR-like (Clipper quirk)
// Array/Hash/Block/Pointer: pointer identity
func valueEqual(a, b Value) bool {
	at, bt := a.Type(), b.Type()

	// NIL handling
	if at == tNil && bt == tNil {
		return true
	}
	if at == tNil || bt == tNil {
		return false
	}

	// Numeric cross-type comparison
	if a.IsNumeric() && b.IsNumeric() {
		if a.IsNumInt() && b.IsNumInt() {
			return a.AsNumInt() == b.AsNumInt()
		}
		return a.AsNumDouble() == b.AsNumDouble()
	}

	// Same type required from here
	if at != bt {
		return false
	}

	switch at {
	case tString:
		return a.AsString() == b.AsString()

	case tDate:
		return a.AsJulian() == b.AsJulian()

	case tTimestamp:
		return a.AsJulian() == b.AsJulian() && a.AsTimeMs() == b.AsTimeMs()

	case tLogical:
		// Harbour/Clipper quirk: XOR-like behavior
		// .T. = .T. → .T.    .F. = .F. → .T.
		// .T. = .F. → .F.    .F. = .T. → .F.
		return a.AsBool() == b.AsBool()

	case tArray, tObject:
		// Pointer identity
		return a.ptr == b.ptr

	case tHash:
		return a.ptr == b.ptr

	case tBlock:
		return a.ptr == b.ptr

	case tPointer:
		return a.scalar == b.scalar
	}

	return false
}

// valueExactEqual is like valueEqual but arrays/objects cannot override.
// Harbour: hb_vmExactlyEqual
func valueExactEqual(a, b Value) bool {
	// For strings, exact equality checks full length (ignoring SET EXACT)
	if a.IsString() && b.IsString() {
		return a.AsString() == b.AsString()
	}
	return valueEqual(a, b)
}

// valueCompare returns comparison result (-1, 0, +1) and whether comparison is valid.
// Only String, Numeric, Date, Timestamp support ordering.
// Harbour: hb_vmLess, hb_vmGreater, etc. (hvm.c:4176+)
func valueCompare(a, b Value) (int, bool) {
	// Numeric comparison
	if a.IsNumeric() && b.IsNumeric() {
		if a.IsNumInt() && b.IsNumInt() {
			return compareInt64(a.AsNumInt(), b.AsNumInt()), true
		}
		return compareFloat64(a.AsNumDouble(), b.AsNumDouble()), true
	}

	at, bt := a.Type(), b.Type()
	if at != bt {
		return 0, false // type mismatch → error
	}

	switch at {
	case tString:
		return strings.Compare(a.AsString(), b.AsString()), true

	case tDate:
		return compareInt64(a.AsJulian(), b.AsJulian()), true

	case tTimestamp:
		cmp := compareInt64(a.AsJulian(), b.AsJulian())
		if cmp != 0 {
			return cmp, true
		}
		return compareInt32(a.AsTimeMs(), b.AsTimeMs()), true
	}

	return 0, false // unsupported type for ordering
}

// --- Primitive comparison helpers ---
// Following tsgo pattern of small, inlineable helper functions.

func compareInt64(a, b int64) int {
	if a < b {
		return -1
	}
	if a > b {
		return 1
	}
	return 0
}

func compareInt32(a, b int32) int {
	if a < b {
		return -1
	}
	if a > b {
		return 1
	}
	return 0
}

func compareFloat64(a, b float64) int {
	if a < b {
		return -1
	}
	if a > b {
		return 1
	}
	return 0
}