salix/expr.go

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/*
* 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/>.
*/
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package salix
import (
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"errors"
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"reflect"
"strings"
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"go.elara.ws/salix/ast"
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)
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var (
ErrModulusFloat = errors.New("modulo operation cannot be performed on floats")
ErrTypeMismatch = errors.New("mismatched types")
ErrLogicalNonBool = errors.New("logical operations may only be performed on boolean values")
ErrInOpInvalidTypes = errors.New("the in operator can only be used on strings, arrays, and slices")
)
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func (t *Template) evalExpr(expr ast.Expr, local map[string]any) (any, error) {
val, err := t.getValue(expr.First, local)
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if err != nil {
return nil, err
}
a := reflect.ValueOf(val)
for _, exprB := range expr.Rest {
val, err := t.getValue(exprB.First, local)
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if err != nil {
return nil, err
}
b := reflect.ValueOf(val)
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result, err := t.performOp(a, b, exprB.Operator)
if err != nil {
return nil, err
}
a = reflect.ValueOf(result)
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}
return a.Interface(), nil
}
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func (t *Template) performOp(a, b reflect.Value, op ast.Operator) (any, error) {
if op.Value == "in" {
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switch b.Kind() {
case reflect.Slice, reflect.Array:
if a.CanConvert(b.Type().Elem()) {
a = a.Convert(b.Type().Elem())
} else {
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return nil, t.posError(op, "%w (%s and %s)", ErrTypeMismatch, a.Type(), b.Type())
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}
case reflect.String:
if a.Kind() != reflect.String {
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return nil, t.posError(op, "%w (%s and %s)", ErrTypeMismatch, a.Type(), b.Type())
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}
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default:
return nil, t.posError(op, "%w (got %s and %s)", ErrInOpInvalidTypes, a.Type(), b.Type())
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}
} else if b.CanConvert(a.Type()) {
b = b.Convert(a.Type())
} else {
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return nil, t.posError(op, "%w (%s and %s)", ErrTypeMismatch, a.Type(), b.Type())
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}
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switch op.Value {
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case "==":
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return a.Equal(b), nil
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case "&&":
if a.Kind() != reflect.Bool || b.Kind() != reflect.Bool {
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return nil, t.posError(op, "%w", ErrLogicalNonBool)
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}
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return a.Bool() && b.Bool(), nil
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case "||":
if a.Kind() != reflect.Bool || b.Kind() != reflect.Bool {
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return nil, t.posError(op, "%w", ErrLogicalNonBool)
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}
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return a.Bool() || b.Bool(), nil
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case ">=":
switch a.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return a.Int() >= b.Int(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return a.Uint() >= b.Uint(), nil
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case reflect.Float64, reflect.Float32:
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return a.Float() >= b.Float(), nil
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}
case "<=":
switch a.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return a.Int() <= b.Int(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return a.Uint() <= b.Uint(), nil
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case reflect.Float64, reflect.Float32:
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return a.Float() <= b.Float(), nil
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}
case ">":
switch a.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return a.Int() > b.Int(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return a.Uint() > b.Uint(), nil
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case reflect.Float64, reflect.Float32:
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return a.Float() > b.Float(), nil
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}
case "<":
switch a.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return a.Int() < b.Int(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return a.Uint() < b.Uint(), nil
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case reflect.Float64, reflect.Float32:
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return a.Float() < b.Float(), nil
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}
case "+":
switch a.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return a.Int() + b.Int(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return a.Uint() + b.Uint(), nil
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case reflect.Float64, reflect.Float32:
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return a.Float() + b.Float(), nil
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}
case "-":
switch a.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return a.Int() - b.Int(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return a.Uint() - b.Uint(), nil
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case reflect.Float64, reflect.Float32:
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return a.Float() - b.Float(), nil
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}
case "*":
switch a.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return a.Int() * b.Int(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return a.Uint() * b.Uint(), nil
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case reflect.Float64, reflect.Float32:
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return a.Float() * b.Float(), nil
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}
case "/":
switch a.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return a.Int() / b.Int(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return a.Uint() / b.Uint(), nil
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case reflect.Float64, reflect.Float32:
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return a.Float() / b.Float(), nil
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}
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case "%":
switch a.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return a.Int() % b.Int(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return a.Uint() % b.Uint(), nil
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case reflect.Float64, reflect.Float32:
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return nil, t.posError(op, "%w", ErrModulusFloat)
}
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case "in":
if a.Kind() == reflect.String && b.Kind() == reflect.String {
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return strings.Contains(b.String(), a.String()), nil
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} else {
for i := 0; i < b.Len(); i++ {
if a.Equal(b.Index(i)) {
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return true, nil
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}
}
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return false, nil
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}
}
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return false, nil
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}