/*
 Serene --- Yet an other Lisp

Copyright (c) 2020  Sameer Rahmani <lxsameer@gnu.org>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

package core

import (
	"fmt"

	"serene-lang.org/bootstrap/pkg/ast"
)

// Def defines a global binding in the current namespace. The first
// arguments in `args` has to be a symbol ( none ns qualified ) and
// the second param should be the value of the binding
func Def(rt *Runtime, scope IScope, args *List) (IExpr, IError) {
	// TODO: Add support for docstrings and meta
	switch args.Count() {
	case 2:
		name := args.First()

		if name.GetType() != ast.Symbol {
			return nil, MakeError(rt, name, "the first argument of 'def' has to be a symbol")
		}

		sym := name.(*Symbol)

		valueExpr := args.Rest().First()
		value, err := EvalForms(rt, scope, valueExpr)

		if err != nil {
			return nil, err
		}

		if value.GetType() == ast.Fn {
			value.(*Function).SetName(sym.GetName())
		}

		ns := rt.CurrentNS()
		ns.DefineGlobal(sym.GetName(), value, true)
		return sym, nil
	}

	return nil, MakeError(rt, args, "'def' form need at least 2 arguments")
}

// Def defines a macro in the current namespace. The first
// arguments in `args` has to be a symbol ( none ns qualified ) and
// the rest of params should be the body of the macro. Unlike other
// expressions in Serene `defmacro` DOES NOT evaluate its arguments.
// That is what makes macros great
func DefMacro(rt *Runtime, scope IScope, args *List) (IExpr, IError) {

	// TODO: Add support for docstrings and meta

	if args.Count() < 2 {
		return nil, MakeError(rt, args, "'defmacro' form need at least 2 arguments")
	}

	name := args.Rest().First()

	if name.GetType() != ast.Symbol {
		return nil, MakeError(rt, name, "the first argument of 'defmacro' has to be a symbol")
	}

	sym := name.(*Symbol)

	var params IColl
	body := MakeEmptyBlock()

	arguments := args.Rest().Rest().First()

	// TODO: Add vector in here
	// Or any other icoll
	if arguments.GetType() == ast.List {
		params = arguments.(IColl)
	}

	if args.Count() > 2 {
		body.SetContent(args.Rest().Rest().Rest().(*List).ToSlice())
	}

	macro := MakeMacro(scope, sym.GetName(), params, body)

	ns := scope.GetNS(rt)
	ns.DefineGlobal(sym.GetName(), macro, true)

	return macro, nil

}

// Fn defines a function inside the given scope `scope` with the given `args`.
// `args` contains the arugment list, docstring and body of the function.
func Fn(rt *Runtime, scope IScope, args *List) (IExpr, IError) {

	if args.Count() < 2 {
		return nil, MakeError(rt, args, "'fn' needs at least an arguments list")
	}

	var params IColl
	body := MakeEmptyBlock()

	arguments := args.Rest().First()

	// TODO: Add vector in here
	// Or any other icoll
	if arguments.GetType() == ast.List {
		params = arguments.(IColl)
	}

	if args.Count() > 1 {
		body.SetContent(args.Rest().Rest().(*List).ToSlice())
	}

	return MakeFunction(MakeNodeFromExpr(args.First()), scope, params, body), nil
}

func NSForm(rt *Runtime, scope IScope, args *List) (IExpr, IError) {
	if args.Count() == 1 {
		return nil, MakeError(rt, args, "namespace's name is missing")
	}

	name := args.Rest().First()

	if name.GetType() != ast.Symbol {
		return nil, MakeError(rt, name, "the first argument to the 'ns' has to be a symbol")
	}
	nsName := name.(*Symbol).GetName()

	if nsName != rt.CurrentNS().GetName() {
		return nil, MakeError(
			rt,
			args,
			fmt.Sprintf("the namespace '%s' doesn't match the file name.", nsName),
		)
	}
	ns, ok := rt.GetNS(nsName)

	if !ok {
		return nil, MakeError(rt, name, fmt.Sprintf("can't find the namespace '%s'. Is it the same as the file name?", nsName))
	}

	return ns, nil
	// TODO: Handle the params like `require` and `meta`
	// params := args.Rest().Rest()

}