feat: json::from_string

quartz/json.qz

@@ -58,5 +58,314 @@ module Json {
  fun to_string(self): string {
  return self.to_string_internal();
  }
+
+ fun from_string(str: string): Json or error {
+ return JsonParser::parse(str);
+ }
+}
+
+enum JsonToken {
+ t_null: bool,
+ t_lbracket: bool,
+ t_rbracket: bool,
+ t_lbrace: bool,
+ t_rbrace: bool,
+ t_comma: bool,
+ t_colon: bool,
+ t_i32: i32,
+ t_string: string,
+}
+
+struct JsonTokenizer {
+ str: string,
+ position: i32,
+}
+
+module JsonTokenizer {
+ fun new(str: string): JsonTokenizer {
+ return JsonTokenizer {
+ str: str,
+ position: 0,
+ };
+ }
+
+ fun tokenize(self): vec[JsonToken] or error {
+ let tokens = make[vec[JsonToken]]();
+
+ while self.position < self.str.length {
+ let c = self.peek().try;
+
+ if c == " " || c == "\n" || c == "\t" {
+ self.position = self.position + 1;
+ continue;
+ } else if c == "{" {
+ tokens.push(JsonToken {
+ t_lbrace: true,
+ });
+ self.position = self.position + 1;
+ } else if c == "}" {
+ tokens.push(JsonToken {
+ t_rbrace: true,
+ });
+ self.position = self.position + 1;
+ } else if c == "[" {
+ tokens.push(JsonToken {
+ t_lbracket: true,
+ });
+ self.position = self.position + 1;
+ } else if c == "]" {
+ tokens.push(JsonToken {
+ t_rbracket: true,
+ });
+ self.position = self.position + 1;
+ } else if c == "," {
+ tokens.push(JsonToken {
+ t_comma: true,
+ });
+ self.position = self.position + 1;
+ } else if c == ":" {
+ tokens.push(JsonToken {
+ t_colon: true,
+ });
+ self.position = self.position + 1;
+ } else if c == "\"" {
+ let builder = stringbuilder::new();
+ self.position = self.position + 1;
+
+ let c = self.peek().try;
+ while c != "\"" {
+ if c == "\\" {
+ let next = self.peek().try;
+ if next == "\"" {
+ builder.append("\"");
+ self.position = self.position + 1;
+ continue;
+ }
+ }
+
+ builder.append(c);
+ self.position = self.position + 1;
+
+ c = self.peek().try;
+ }
+
+ self.position = self.position + 1;
+
+ tokens.push(JsonToken {
+ t_string: builder.to_string(),
+ });
+ } else if c == "n" {
+ let n = self.peek_n(4).try;
+ if n != "null" {
+ return _ or error::new("expected null");
+ }
+
+ self.position = self.position + 4;
+ tokens.push(JsonToken {
+ t_null: true,
+ });
+ } else {
+ let builder = stringbuilder::new();
+ let c = self.peek().try;
+ let b = c.(0) as i32;
+
+ while b >= 48 && b <= 57 && self.position < self.str.length {
+ builder.append(c);
+ self.position = self.position + 1;
+
+ c = self.peek().try;
+ b = c.(0) as i32;
+ }
+
+ tokens.push(JsonToken {
+ t_i32: i32::parse(builder.to_string()),
+ });
+ }
+ }
+
+ return tokens;
+ }
+
+ fun peek(self): string or error {
+ if self.position > self.str.length {
+ return _ or error::new("unexpected end of input, {}".format(self.position.to_string()));
+ }
+
+ return self.str.slice(self.position, self.position + 1);
+ }
+
+ fun peek_n(self, length: i32): string or error {
+ if self.position + length > self.str.length {
+ return _ or error::new("unexpected end of input");
+ }
+
+ return self.str.slice(self.position, self.position + length);
+ }
+}
+
+struct JsonParser {
+ tokens: vec[JsonToken],
+ position: i32,
+}
+
+module JsonParser {
+ fun new(tokens: vec[JsonToken]): JsonParser {
+ return JsonParser {
+ tokens: tokens,
+ position: 0,
+ };
+ }
+
+ fun parse(str: string): Json or error {
+ let tokenizer = JsonTokenizer::new(str);
+ let tokens = tokenizer.tokenize().try;
+ let parser = JsonParser::new(tokens);
+ return parser.json();
+ }
+
+ fun peek(self): JsonToken or error {
+ if self.position > self.tokens.length {
+ return _ or error::new("unexpected end of input");
+ }
+
+ return self.tokens.at(self.position);
+ }
+
+ fun json(self): Json or error {
+ let token = self.peek().try;
+ if token.t_null != nil {
+ self.position = self.position + 1;
+
+ return Json {
+ t_nil: nil,
+ };
+ } else if token.t_i32 != nil {
+ self.position = self.position + 1;
+
+ return Json {
+ t_i32: token.t_i32!,
+ };
+ } else if token.t_string != nil {
+ self.position = self.position + 1;
+
+ return Json {
+ t_string: token.t_string!,
+ };
+ } else if token.t_lbracket != nil {
+ return self.parse_array();
+ } else if token.t_lbrace != nil {
+ return self.parse_object();
+ }
+
+ return _ or error::new("unexpected token");
+ }
+
+ fun parse_object(self): Json or error {
+ let obj = make[map[string, Json]]();
+ self.position = self.position + 1;
+
+ while true {
+ let c = self.peek().try;
+ if c.t_rbrace != nil {
+ self.position = self.position + 1;
+ break;
+ } else if c.t_comma != nil {
+ self.position = self.position + 1;
+ continue;
+ }
+
+ let key = self.peek().try;
+ if key.t_string == nil {
+ return _ or error::new("expected string");
+ }
+ self.position = self.position + 1;
+
+ let c = self.peek().try;
+ if c.t_colon == nil {
+ return _ or error::new("expected ':', got '{}'".format(derive::to_string(c)));
+ }
+ self.position = self.position + 1;
+
+ let value = self.json().try;
+ obj.insert(key.t_string!, value);
+ }
+
+ return Json {
+ t_object: obj,
+ };
+ }
+
+ fun parse_array(self): Json or error {
+ let arr = make[vec[Json]]();
+ self.position = self.position + 1;
+
+ while true {
+ let c = self.peek().try;
+ if c.t_rbracket != nil {
+ self.position = self.position + 1;
+ break;
+ } else if c.t_comma != nil {
+ self.position = self.position + 1;
+ continue;
+ }
+
+ let value = self.json().try;
+ arr.push(value);
+ }
+
+ return Json {
+ t_array: arr,
+ };
+ }
+}
+
+@[test]
+fun test_json_from_string() {
+ assert_eq(
+ Json::from_string("null"),
+ Json {
+ t_nil: nil,
+ } or _,
+ );
+ assert_eq(
+ Json::from_string("123"),
+ Json {
+ t_i32: 123,
+ } or _,
+ );
+ assert_eq(
+ Json::from_string("\"hello\""),
+ Json {
+ t_string: "hello",
+ } or _,
+ );
+ assert_eq(
+ Json::from_string("[1,\"hello\",null]"),
+ Json {
+ t_array: make[vec[Json]](
+ Json {
+ t_i32: 1,
+ },
+ Json {
+ t_string: "hello",
+ },
+ Json {
+ t_nil: nil,
+ },
+ ),
+ } or _,
+ );
+
+ let object = make[map[string, Json]]();
+ object.("hello") = Json {
+ t_i32: 123,
+ };
+
+ assert_eq(
+ Json::from_string("{\"hello\":123}"),
+ Json {
+ t_object: object,
+ } or _,
+ );
 }