salix/for_tag.go

/*
 * Salix - Go templating engine
 * Copyright (C) 2023 Elara Musayelyan
 *
 * 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 3 of the License, or
 * (at your option) any later version.
 *
 * 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 salix

import (
	"reflect"

	"go.elara.ws/salix/ast"
)

// forTag represents a #for tag within a Salix template
type forTag struct{}

func (ft forTag) Run(tc *TagContext, block, args []ast.Node) error {
	if len(args) == 0 || len(args) > 2 {
		return tc.PosError(tc.Tag, "invalid argument amount")
	}

	var expr ast.Expr
	if len(args) == 1 {
		expr2, ok := args[0].(ast.Expr)
		if !ok {
			return tc.PosError(args[0], "invalid argument type: %T (expected ast.Expr)", args[0])
		}
		expr = expr2
	} else if len(args) == 2 {
		expr2, ok := args[1].(ast.Expr)
		if !ok {
			return tc.PosError(args[1], "invalid argument type: %T (expected ast.Expr)", args[1])
		}
		expr = expr2
	}

	var vars []string
	var in reflect.Value

	if len(args) == 2 {
		varName, ok := unwrap(args[0]).(ast.Ident)
		if !ok {
			return tc.PosError(args[0], "invalid argument type: %T (expected ast.Ident)", expr.First)
		}
		vars = append(vars, varName.Value)
	}

	varName, ok := unwrap(expr.First).(ast.Ident)
	if !ok {
		return tc.PosError(expr.First, "invalid argument type: %T (expected ast.Ident)", args[0])
	}
	vars = append(vars, varName.Value)

	if len(expr.Rest) != 1 {
		return tc.PosError(expr.First, "invalid expression (expected 1 element, got %d)", len(expr.Rest))
	}
	rest := expr.Rest[0]

	if rest.Operator.Value != "in" {
		return tc.PosError(expr.First, `invalid operator in expression (expected "in", got %q)`, rest.Operator.Value)
	}

	val, err := tc.GetValue(rest, nil)
	if err != nil {
		return err
	}
	in = reflect.ValueOf(val)

	switch in.Kind() {
	case reflect.Slice, reflect.Array:
		local := map[string]any{}
		for i := 0; i < in.Len(); i++ {
			if len(vars) == 1 {
				local[vars[0]] = in.Index(i).Interface()
			} else if len(vars) == 2 {
				local[vars[0]] = i
				local[vars[1]] = in.Index(i).Interface()
			}

			err = tc.Execute(block, local)
			if err != nil {
				return err
			}
		}
	case reflect.Map:
		local := map[string]any{}
		iter := in.MapRange()
		for iter.Next() {
			if len(vars) == 1 {
				local[vars[0]] = iter.Value().Interface()
			} else if len(vars) == 2 {
				local[vars[0]] = iter.Key().Interface()
				local[vars[1]] = iter.Value().Interface()
			}

			err = tc.Execute(block, local)
			if err != nil {
				return err
			}
		}
	}

	return nil
}

func unwrap(n ast.Node) ast.Node {
	if v, ok := n.(ast.Value); ok {
		return v.Node
	}
	return n
}