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Common Expression Language Runtime for Java
// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package dev.cel.common.ast;
import com.google.common.collect.ImmutableSet;
/** Provides string formatting support for {@link CelExpr}. */
final class CelExprFormatter {
private final StringBuilder indent = new StringBuilder();
private final StringBuilder exprBuilder = new StringBuilder();
/** Denotes a set of expression kinds that will not have a new line inserted. */
private static final ImmutableSet EXCLUDED_NEWLINE_KINDS =
ImmutableSet.of(CelExpr.ExprKind.Kind.CONSTANT, CelExpr.ExprKind.Kind.NOT_SET);
static String format(CelExpr celExpr) {
CelExprFormatter formatter = new CelExprFormatter();
formatter.formatExpr(celExpr);
return formatter.exprBuilder.toString();
}
private void formatExpr(CelExpr celExpr) {
append(String.format("%s [%d] {", celExpr.exprKind().getKind(), celExpr.id()));
CelExpr.ExprKind.Kind exprKind = celExpr.exprKind().getKind();
if (!EXCLUDED_NEWLINE_KINDS.contains(exprKind)) {
appendNewline();
}
switch (exprKind) {
case CONSTANT:
appendConst(celExpr.constant());
break;
case IDENT:
appendIdent(celExpr.ident());
break;
case SELECT:
appendSelect(celExpr.select());
break;
case CALL:
appendCall(celExpr.call());
break;
case CREATE_LIST:
appendCreateList(celExpr.createList());
break;
case CREATE_STRUCT:
appendCreateStruct(celExpr.createStruct());
break;
case CREATE_MAP:
appendCreateMap(celExpr.createMap());
break;
case COMPREHENSION:
appendComprehension(celExpr.comprehension());
break;
case NOT_SET:
break;
default:
// This should be unreachable unless if we've added any other kinds.
indent();
append("Unknown kind: " + exprKind);
outdent();
break;
}
if (!EXCLUDED_NEWLINE_KINDS.contains(exprKind)) {
appendNewline();
append("}");
} else {
appendWithoutIndent("}");
}
}
private void appendConst(CelConstant celConstant) {
appendWithoutIndent(" value: ");
switch (celConstant.getKind()) {
case NULL_VALUE:
appendWithoutIndent("null");
break;
case BOOLEAN_VALUE:
appendWithoutIndent(Boolean.toString(celConstant.booleanValue()));
break;
case INT64_VALUE:
appendWithoutIndent(Long.toString(celConstant.int64Value()));
break;
case UINT64_VALUE:
appendWithoutIndent(celConstant.uint64Value() + "u");
break;
case DOUBLE_VALUE:
appendWithoutIndent(Double.toString(celConstant.doubleValue()));
break;
case STRING_VALUE:
appendWithoutIndent("\"" + celConstant.stringValue() + "\"");
break;
case BYTES_VALUE:
appendWithoutIndent(String.format("b\"%s\"", celConstant.bytesValue().toStringUtf8()));
break;
default:
append("Unknown kind: " + celConstant.getKind());
break;
}
appendWithoutIndent(" ");
}
private void appendIdent(CelExpr.CelIdent celIdent) {
indent();
append("name: " + celIdent.name());
outdent();
}
private void appendSelect(CelExpr.CelSelect celSelect) {
indent();
formatExpr(celSelect.operand());
outdent();
appendWithoutIndent(".");
appendWithoutIndent(celSelect.field());
if (celSelect.testOnly()) {
appendWithoutIndent("~presence_test");
}
}
private void appendCall(CelExpr.CelCall celCall) {
indent();
appendWithNewline("function: " + celCall.function());
if (celCall.target().isPresent()) {
appendWithNewline("target: {");
indent();
formatExpr(celCall.target().get());
outdent();
appendNewline();
appendWithNewline("}");
}
append("args: {");
indent();
for (CelExpr celExpr : celCall.args()) {
appendNewline();
formatExpr(celExpr);
}
outdent();
appendNewline();
append("}");
outdent();
}
private void appendCreateList(CelExpr.CelCreateList celCreateList) {
indent();
append("elements: {");
indent();
for (CelExpr expr : celCreateList.elements()) {
appendNewline();
formatExpr(expr);
}
outdent();
appendNewline();
append("}");
if (!celCreateList.optionalIndices().isEmpty()) {
appendNewline();
append("optional_indices: [");
for (int i = 0; i < celCreateList.optionalIndices().size(); i++) {
appendWithoutIndent(String.valueOf(i));
if (i != celCreateList.optionalIndices().size() - 1) {
appendWithoutIndent(", ");
}
}
appendWithoutIndent("]");
}
outdent();
}
private void appendCreateStruct(CelExpr.CelCreateStruct celCreateStruct) {
indent();
appendWithNewline("name: " + celCreateStruct.messageName());
append("entries: {");
indent();
for (CelExpr.CelCreateStruct.Entry entry : celCreateStruct.entries()) {
appendNewline();
appendWithNewline(String.format("ENTRY [%d] {", entry.id()));
indent();
appendWithNewline("field_key: " + entry.fieldKey());
if (entry.optionalEntry()) {
appendWithNewline("optional_entry: true");
}
appendWithNewline("value: {");
indent();
formatExpr(entry.value());
outdent();
appendNewline();
appendWithNewline("}");
outdent();
append("}");
}
outdent();
appendNewline();
append("}");
outdent();
}
private void appendCreateMap(CelExpr.CelCreateMap celCreateMap) {
indent();
boolean firstLine = true;
for (CelExpr.CelCreateMap.Entry entry : celCreateMap.entries()) {
if (!firstLine) {
appendNewline();
} else {
firstLine = false;
}
appendWithNewline(String.format("MAP_ENTRY [%d] {", entry.id()));
indent();
appendWithNewline("key: {");
indent();
formatExpr(entry.key());
outdent();
appendNewline();
appendWithNewline("}");
if (entry.optionalEntry()) {
appendWithNewline("optional_entry: true");
}
appendWithNewline("value: {");
indent();
formatExpr(entry.value());
outdent();
appendNewline();
appendWithNewline("}");
outdent();
append("}");
}
outdent();
}
private void appendComprehension(CelExpr.CelComprehension celComprehension) {
indent();
appendWithNewline("iter_var: " + celComprehension.iterVar());
// Iter range
appendWithNewline("iter_range: {");
indent();
formatExpr(celComprehension.iterRange());
outdent();
appendNewline();
appendWithNewline("}");
appendWithNewline("accu_var: " + celComprehension.accuVar());
// Accu init
appendWithNewline("accu_init: {");
indent();
formatExpr(celComprehension.accuInit());
outdent();
appendNewline();
appendWithNewline("}");
// Loop condition
appendWithNewline("loop_condition: {");
indent();
formatExpr(celComprehension.loopCondition());
outdent();
appendNewline();
appendWithNewline("}");
// Loop step
appendWithNewline("loop_step: {");
indent();
formatExpr(celComprehension.loopStep());
outdent();
appendNewline();
appendWithNewline("}");
// Result
appendWithNewline("result: {");
indent();
formatExpr(celComprehension.result());
outdent();
appendNewline();
append("}");
outdent();
}
private void append(String str) {
exprBuilder.append(indent);
exprBuilder.append(str);
}
private void appendWithNewline(String str) {
append(str);
appendNewline();
}
private void appendWithoutIndent(String str) {
exprBuilder.append(str);
}
private void appendNewline() {
exprBuilder.append('\n');
}
private void indent() {
indent.append(" ");
}
private void outdent() {
indent.setLength(indent.length() - 2);
}
private CelExprFormatter() {}
}