jq path wip
parent
92a20c82f8
commit
5a5d1492a5
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package eu.jonahbauer.json;
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import lombok.EqualsAndHashCode;
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import org.jetbrains.annotations.NotNull;
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import org.jetbrains.annotations.Nullable;
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import java.util.*;
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@EqualsAndHashCode
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public final class JsonPath {
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public static final JsonPath EMPTY = new JsonPath(Collections.emptyList());
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private final @NotNull List<@NotNull Component> components;
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public static @NotNull JsonPath parse(@NotNull String path) {
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var components = new ArrayList<Component>();
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var reader = new StringReader(path);
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if (reader.hasNext()) {
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if (reader.next() == '.' && !reader.hasNext()) return JsonPath.EMPTY;
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reader.pushback();
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}
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do {
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if (reader.next() != '.') throw unexpectedCharacter(reader.current(), "'.'");
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components.add(switch (reader.next()) {
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// object access with string
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case '"' -> {
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reader.pushback();
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yield new Component.ObjectAccess(readString(reader));
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}
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case '[' -> {
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var out = switch (reader.next()) {
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// object access with string
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case '"' -> {
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reader.pushback();
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yield new Component.ObjectAccess(readString(reader));
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}
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// array access with index
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case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' -> {
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var negative = reader.current() == '-';
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if (negative) reader.pushback();
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var index = readInteger(reader);
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yield new Component.ArrayAccess(index, negative && index != 0);
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}
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default -> throw unexpectedCharacter(reader.current(), "'\"' or '1'-'9'");
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};
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if (reader.next() != ']') throw unexpectedCharacter(reader.current(), "']'");
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yield out;
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}
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// object access with identifier
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default -> {
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var chr = reader.current();
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if (chr == '_' || 'a' <= chr && chr <= 'z' || 'A' <= chr && chr <= 'Z') {
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yield new Component.ObjectAccess(readIdentifier(reader));
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} else {
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throw unexpectedCharacter(chr, "one of '\"', '[', '_', 'a'-'z' or 'A'-'Z'");
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}
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}
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});
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} while (reader.hasNext());
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return new JsonPath(Collections.unmodifiableList(components));
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}
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private JsonPath(@NotNull List<@NotNull Component> components) {
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this.components = components;
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}
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public @Nullable JsonValue select(@Nullable JsonValue value) {
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for (Component component : components) {
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value = component.select(value);
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}
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return value;
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}
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public @NotNull JsonPath resolve(@NotNull String key) {
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var components = new ArrayList<Component>(this.components.size() + 1);
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components.addAll(this.components);
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components.add(new Component.ObjectAccess(key));
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return new JsonPath(Collections.unmodifiableList(components));
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}
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public @NotNull JsonPath resolve(int index) {
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var components = new ArrayList<Component>(this.components.size() + 1);
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components.addAll(this.components);
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components.add(new Component.ArrayAccess(Math.abs(index), index < 0));
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return new JsonPath(Collections.unmodifiableList(components));
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}
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private sealed interface Component {
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@Nullable JsonValue select(@Nullable JsonValue value);
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record ArrayAccess(int index, boolean end) implements Component {
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@Override
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public @Nullable JsonValue select(@Nullable JsonValue value) {
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if (value instanceof JsonArray array) {
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if (end) return array.get(array.size() - index);
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return array.get(index);
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} else {
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throw new JsonProcessingException("unexpected type");
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}
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}
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@Override
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public String toString() {
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return "[" + index + "]";
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}
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}
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record ObjectAccess(@NotNull String key) implements Component {
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@Override
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public @Nullable JsonValue select(@Nullable JsonValue value) {
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if (value instanceof JsonObject object) {
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return object.get(key);
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} else {
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throw new JsonProcessingException("unexpected type");
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}
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}
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@Override
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public String toString() {
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return ".[\"" + JsonString.quote(key) + "\"]";
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}
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}
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}
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private static int readInteger(@NotNull StringReader reader) {
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var i = reader.next() - '0';
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while (reader.hasNext()) {
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var chr = reader.next();
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if (chr < '0' || chr > '9') {
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reader.pushback();
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break;
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} else if (i == 0) {
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throw unexpectedCharacter(chr, "']'");
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} else {
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i = Math.multiplyExact(i, 10);
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i = Math.addExact(i, chr - '0');
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}
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}
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return i;
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}
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private static @NotNull String readString(@NotNull StringReader reader) {
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var out = new StringBuilder();
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if (reader.next() != '"') throw new IllegalStateException();
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while (true) {
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char chr = reader.next();
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if (chr == '"') {
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return out.toString();
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} else if (chr == '\\') {
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out.append(switch (reader.next()) {
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case '"' -> '"';
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case '\\' -> '\\';
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case '/' -> '/';
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case 'b' -> '\b';
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case 'f' -> '\f';
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case 'n' -> '\n';
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case 'r' -> '\r';
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case 't' -> '\t';
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case 'u' -> {
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var u0 = toHex(reader.next());
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var u1 = toHex(reader.next());
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var u2 = toHex(reader.next());
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var u3 = toHex(reader.next());
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yield (char) ((u0 << 12) + (u1 << 8) + (u2 << 4) + u3);
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}
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default -> throw unexpectedCharacter(reader.current(), "one of '\"', '\\', '/', 'b', 'f', 'n', 'r', 't' or 'u'");
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});
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} else if (chr < 32) {
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throw new JsonProcessingException("unescaped control character in string literal");
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} else {
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out.append(chr);
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}
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}
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}
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private static int toHex(char chr) {
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if ('0' <= chr && chr <= '9') {
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return chr - '0';
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} else if ('a' <= chr && chr <= 'f') {
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return 11 + chr - 'a';
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} else if ('A' <= chr && chr <= 'F') {
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return 11 + chr - 'A';
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} else {
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throw unexpectedCharacter(chr, "one of '0'-'9', 'a'-'f' or 'A'-'F'");
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}
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}
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private static @NotNull String readIdentifier(@NotNull StringReader reader) {
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var out = new StringBuilder();
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out.append(reader.next());
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while (reader.hasNext()) {
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var chr = reader.next();
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if (chr == '_' || 'a' <= chr && chr <= 'z' || 'A' <= chr && chr <= 'Z' || '0' <= chr && chr <= '9') {
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out.append(chr);
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} else {
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throw unexpectedCharacter(chr, "one of '.', '_', 'a'-'z', 'A'-'Z' or '0'-'9'");
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}
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}
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return out.toString();
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}
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private static JsonProcessingException unexpectedCharacter(char character, String expected) {
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return new JsonProcessingException("unexpected character '" + character + "' (expected " + expected + ")");
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}
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private static class StringReader {
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private final String string;
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private final int length;
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private int index;
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public StringReader(String string) {
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this.string = string;
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this.length = string.length();
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}
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public void pushback() {
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if (index == 0) throw new IllegalStateException();
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index--;
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}
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public char next() {
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if (index >= length) {
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throw new JsonProcessingException("unexpected end of string");
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}
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return string.charAt(index++);
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}
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public char current() {
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return string.charAt(index - 1);
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}
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public boolean hasNext() {
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return index < length;
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}
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}
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}
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@ -0,0 +1,75 @@
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package eu.jonahbauer.json.parser;
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import eu.jonahbauer.json.*;
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import org.junit.jupiter.api.Test;
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import java.util.List;
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import java.util.Map;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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class JsonPathTest {
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private final JsonValue array = new JsonArray(List.of(
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new JsonNumber(1),
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new JsonNumber(2),
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new JsonObject(Map.of(
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"bar", JsonBoolean.FALSE
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))
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));
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private final JsonValue object = new JsonObject(Map.of(
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"foo", array,
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"bar", new JsonString("baz"),
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"quack quack", new JsonString("foobar")
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));;
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@Test
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void parseEmptyShouldFail() {
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assertThrows(JsonProcessingException.class, () -> JsonPath.parse(""));
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}
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@Test
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void parseIdentity() {
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var path = JsonPath.parse(".");
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assertEquals(object, path.select(object));
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}
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@Test
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void parseArrayAccess() {
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var path = JsonPath.parse(".[0]");
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assertEquals(new JsonNumber(1), path.select(array));
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}
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@Test
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void parseArrayAccessWithLeadingZero() {
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assertThrows(JsonProcessingException.class, () -> JsonPath.parse(".[01]"));
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}
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@Test
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void parseObjectAccessWithIdentifier() {
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var path = JsonPath.parse(".bar");
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assertEquals(new JsonString("baz"), path.select(object));
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}
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@Test
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void parseObjectAccessWithString() {
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var path = JsonPath.parse(".\"quack quack\"");
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assertEquals(new JsonString("foobar"), path.select(object));
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}
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@Test
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void parseObjectAccessWithArraySyntax() {
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var path = JsonPath.parse(".[\"quack quack\"]");
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assertEquals(new JsonString("foobar"), path.select(object));
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assertThrows(JsonProcessingException.class, () -> JsonPath.parse(".[quack quack]"));
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}
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@Test
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void parseChainedAccess() {
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var path = JsonPath.parse(".foo[2].bar");
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assertEquals(JsonBoolean.FALSE, path.select(object));
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}
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}
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