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

// macroeval.go — Full runtime macro compiler for Five.
//
// Implements &(expression) by reusing Five's own lexer/parser at runtime.
// This is the key advantage of Five: since the compiler is in Go,
// it can be embedded in the runtime for macro compilation.
//
// Harbour's macro compiler (src/macro/macro.y) is a separate YACC grammar.
// Five simply reuses the same parser.
//
// Usage:
//   &cVar              → simple variable lookup
//   &(cVar + "_name")  → evaluate string expression, use result as name
//   &("Upper(cName)")  → evaluate function call at runtime

package hbrt

import (
	"five/compiler/ast"
	"five/compiler/parser"
	"five/compiler/token"
	"strconv"
	"strings"
)

// MacroEval compiles and evaluates a Harbour expression string at runtime.
// This is the full macro compiler — uses Five's parser to parse the expression,
// then evaluates the AST directly.
func (t *Thread) MacroEval(exprStr string) Value {
	exprStr = strings.TrimSpace(exprStr)
	if exprStr == "" {
		return MakeNil()
	}

	// Quick path: simple identifier → variable/function lookup
	if isSimpleIdent(exprStr) {
		return t.macroLookupIdent(exprStr)
	}

	// Full path: parse the expression and evaluate the AST
	source := "FUNCTION __macro__()\nRETURN " + exprStr + "\n"
	file, errs := parser.Parse("macro", source)
	if len(errs) > 0 || len(file.Decls) == 0 {
		// Parse failed — try as simple string
		return t.MacroCompile(exprStr)
	}

	fn, ok := file.Decls[0].(*ast.FuncDecl)
	if !ok || len(fn.Body) == 0 {
		return t.MacroCompile(exprStr)
	}

	// Get the RETURN expression
	ret, ok := fn.Body[0].(*ast.ReturnStmt)
	if !ok || ret.Value == nil {
		return t.MacroCompile(exprStr)
	}

	// Evaluate the AST expression
	return t.evalExpr(ret.Value)
}

// evalExpr evaluates an AST expression at runtime.
func (t *Thread) evalExpr(expr ast.Expr) Value {
	switch e := expr.(type) {
	case *ast.LiteralExpr:
		return t.evalLiteral(e)

	case *ast.IdentExpr:
		return t.macroLookupIdent(e.Name)

	case *ast.BinaryExpr:
		left := t.evalExpr(e.Left)
		right := t.evalExpr(e.Right)
		return t.evalBinaryOp(e.Op, left, right)

	case *ast.UnaryExpr:
		x := t.evalExpr(e.X)
		return t.evalUnaryOp(e.Op, x)

	case *ast.CallExpr:
		return t.evalCall(e)

	case *ast.SendExpr:
		obj := t.evalExpr(e.Object)
		args := make([]Value, len(e.Args))
		for i, a := range e.Args {
			args[i] = t.evalExpr(a)
		}
		t.push(obj)
		for _, a := range args {
			t.push(a)
		}
		t.Send(e.Method, len(args))
		return t.pop()

	case *ast.IndexExpr:
		arr := t.evalExpr(e.X)
		idx := t.evalExpr(e.Index)
		if arr.IsArray() {
			items := arr.AsArray().Items
			i := idx.AsInt()
			if i >= 1 && i <= len(items) {
				return items[i-1]
			}
		}
		return MakeNil()

	case *ast.ArrayLitExpr:
		items := make([]Value, len(e.Items))
		for i, item := range e.Items {
			items[i] = t.evalExpr(item)
		}
		return MakeArrayFrom(items)

	case *ast.HashLitExpr:
		h := &HbHash{}
		for i := range e.Keys {
			h.Set(t.evalExpr(e.Keys[i]), t.evalExpr(e.Values[i]))
		}
		return MakeHashFrom(h)

	case *ast.BlockExpr:
		// Return as code block
		body := e.Body
		return MakeBlock(func(bt *Thread) {
			result := bt.evalExpr(body)
			bt.push(result)
			bt.RetValue()
		}, len(e.Params))

	case *ast.DotExpr:
		// pkg.Func — try GoCallFunc
		obj := t.evalExpr(e.X)
		results := GoCall(obj, e.Member)
		if len(results) > 0 {
			return results[0]
		}
		return MakeNil()

	case *ast.SelfExpr:
		return t.self

	case *ast.AliasExpr:
		// alias->field
		if ident, ok := e.Alias.(*ast.IdentExpr); ok {
			if field, ok := e.Field.(*ast.IdentExpr); ok {
				t.PushAliasField(ident.Name, field.Name)
				return t.pop()
			}
		}
		return MakeNil()

	case *ast.AssignExpr:
		val := t.evalExpr(e.Right)
		// Assignment in macro — store to memvar or local
		if ident, ok := e.Left.(*ast.IdentExpr); ok {
			t.macroStoreIdent(ident.Name, val)
		}
		return val

	default:
		return MakeNil()
	}
}

// evalLiteral converts an AST literal to a Value.
func (t *Thread) evalLiteral(e *ast.LiteralExpr) Value {
	switch e.Kind {
	case token.NIL_LIT:
		return MakeNil()
	case token.TRUE:
		return MakeBool(true)
	case token.FALSE:
		return MakeBool(false)
	case token.INT:
		n, _ := strconv.ParseInt(e.Value, 10, 64)
		return MakeNumInt(n)
	case token.LONG:
		n, _ := strconv.ParseInt(e.Value, 10, 64)
		return MakeLong(n)
	case token.DOUBLE:
		f, _ := strconv.ParseFloat(e.Value, 64)
		return MakeDoubleAuto(f)
	case token.STRING:
		return MakeString(e.Value)
	default:
		return MakeString(e.Value)
	}
}

// evalBinaryOp evaluates a binary operation.
func (t *Thread) evalBinaryOp(op token.Kind, left, right Value) Value {
	t.push(left)
	t.push(right)
	switch op {
	case token.PLUS:
		t.Plus()
	case token.MINUS:
		t.Minus()
	case token.STAR:
		t.Mult()
	case token.SLASH:
		t.Divide()
	case token.PERCENT:
		t.Modulus()
	case token.POWER:
		t.Power()
	case token.EQ, token.EXEQ:
		t.Equal()
	case token.NEQ:
		t.NotEqual()
	case token.LT:
		t.Less()
	case token.GT:
		t.Greater()
	case token.LTE:
		t.LessEqual()
	case token.GTE:
		t.GreaterEqual()
	case token.AND:
		t.And()
	case token.OR:
		t.Or()
	case token.DOLLAR:
		t.InString()
	default:
		return MakeNil()
	}
	return t.pop()
}

// evalUnaryOp evaluates a unary operation.
func (t *Thread) evalUnaryOp(op token.Kind, x Value) Value {
	t.push(x)
	switch op {
	case token.MINUS:
		t.Negate()
	case token.NOT:
		t.Not()
	case token.INC:
		t.Inc()
	case token.DEC:
		t.Dec()
	default:
		return x
	}
	return t.pop()
}

// evalCall evaluates a function call expression.
func (t *Thread) evalCall(e *ast.CallExpr) Value {
	// Get function name
	var funcName string
	if ident, ok := e.Func.(*ast.IdentExpr); ok {
		funcName = strings.ToUpper(ident.Name)
	} else {
		return MakeNil()
	}

	// Evaluate arguments
	args := make([]Value, len(e.Args))
	for i, a := range e.Args {
		args[i] = t.evalExpr(a)
	}

	// Find and call function via VM
	sym := t.vm.FindSymbol(funcName)
	if sym == nil || sym.Func == nil {
		return MakeNil()
	}

	t.PushSymbol(sym)
	t.PushNil()
	for _, a := range args {
		t.push(a)
	}
	t.Function(len(args))
	return t.pop()
}

// macroLookupIdent looks up a name: local → memvar → function.
func (t *Thread) macroLookupIdent(name string) Value {
	upper := strings.ToUpper(name)

	// Try memvar first (PUBLIC/PRIVATE)
	if v, ok := t.Memvars.Get(upper); ok {
		return v
	}

	// Try as function
	sym := t.vm.FindSymbol(upper)
	if sym != nil && sym.Func != nil {
		return MakeString(name) // return name (function reference)
	}

	// Return as string (field name, unknown variable)
	return MakeString(name)
}

// macroStoreIdent stores a value to a named variable (memvar).
func (t *Thread) macroStoreIdent(name string, val Value) {
	if !t.Memvars.Set(name, val) {
		t.Memvars.SetPrivate(name, val, t.callSP)
	}
}