// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
// All rights reserved.

// operand-func.go
package expr

import (
	"errors"
	"fmt"
)

// -------- function call term
func newFuncCallTerm(tk *Token, args []*term) *term {
	return &term{
		tk:       *tk,
		parent:   nil,
		children: args,
		position: posLeaf,
		priority: priValue,
		evalFunc: evalFuncCall,
	}
}

// -------- eval func call
func checkFunctionCall(ctx ExprContext, name string, params []any) (err error) {
	if info, exists, owner := GetFuncInfo(ctx, name); exists {
		if info.MinArgs() > len(params) {
			if info.MaxArgs() < 0 {
				err = fmt.Errorf("too few params -- expected %d or more, got %d", info.MinArgs(), len(params))
			} else {
				err = fmt.Errorf("too few params -- expected %d, got %d", info.MinArgs(), len(params))
			}
		}
		if err == nil && info.MaxArgs() >= 0 && info.MaxArgs() < len(params) {
			err = fmt.Errorf("too much params -- expected %d, got %d", info.MaxArgs(), len(params))
		}
		if err == nil && owner != ctx {
			ctx.RegisterFunc(name, info.Functor(), info.MinArgs(), info.MaxArgs())
		}
	} else {
		err = fmt.Errorf("unknown function %s()", name)
	}
	return
}

func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
	ctx := cloneContext(parentCtx)
	name, _ := self.tk.Value.(string)
	// fmt.Printf("Call %s(), context: %p\n", name, ctx)
	params := make([]any, len(self.children))
	for i, tree := range self.children {
		var param any
		if param, err = tree.compute(ctx); err != nil {
			break
		}
		params[i] = param
	}
	if err == nil {
		if err = checkFunctionCall(ctx, name, params); err == nil {
			if v, err = ctx.Call(name, params); err == nil {
				exportObjects(parentCtx, ctx)
			}
		}
	}
	return
}

// -------- function definition term
func newFuncDefTerm(tk *Token, args []*term) *term {
	return &term{
		tk:       *tk, // value is the expression body
		parent:   nil,
		children: args, // function params
		position: posLeaf,
		priority: priValue,
		evalFunc: evalFuncDef,
	}
}

// -------- eval func def
// TODO
type funcDefFunctor struct {
	params []string
	expr   Expr
}

func (functor *funcDefFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
	for i, p := range functor.params {
		if i < len(args) {
			arg := args[i]
			if functor, ok := arg.(Functor); ok {
				ctx.RegisterFunc(p, functor, 0, -1)
			} else {
				ctx.setVar(p, arg)
			}
		} else {
			ctx.setVar(p, nil)
		}
	}
	result, err = functor.expr.eval(ctx, false)
	return
}

func evalFuncDef(ctx ExprContext, self *term) (v any, err error) {
	bodySpec := self.value()
	if expr, ok := bodySpec.(*ast); ok {
		paramList := make([]string, 0, len(self.children))
		for _, param := range self.children {
			paramList = append(paramList, param.source())
		}
		v = &funcDefFunctor{
			params: paramList,
			expr:   expr,
		}
	} else {
		err = errors.New("invalid function definition: the body specification must be an expression")
	}
	return
}