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import java.util.HashMap;
import java.util.ArrayList;
import java.io.*;
/*
* @author
* Kian Agheli
*
* References:
* https://googlefonts.github.io/gf-guide/metadata.html
* https://stackoverflow.com/questions/3880274/how-to-convert-the-object-to-string-in-java
* https://stackoverflow.com/questions/8938498/get-the-index-of-a-pattern-in-a-string-using-regex
* https://howtodoinjava.com/java/regex/start-end-of-string/
*
* Date:
* 2024-05-20
*
* Purpose of class:
* Read from and interpret JSON files.
*/
public class JSONReader extends Reader {
/* metadata.pb is not exactly JSON, but so close to it
that it's practically a subset of JSON with fewer quotation
marks. If set, this is a pb file. */
private boolean isMetadata;
public JSONReader(File file) {
super(file); // Call constructor.
isMetadata = false; // By default, not metadata.
}
private String composeKey(String key) {
/* Call static version. This has the benefit of reducing code size.
Rather than write two separate static and instantiated versions, the
instantiated version may call the static version. */
return composeKey(key, this.isMetadata);
}
private static String composeKey(String key, boolean isMetadata) {
/* JSON usually has quotes surrounding keys. Google's metadata doesn't. */
if (!isMetadata) {
key = "\"" + key + "\"";
}
key += ": ";
return key;
}
/**
* Search for and return the first
* match.
*/
public String get(String key) {
/* Call static version. */
return JSONReader.get(this.getContents(), key, isMetadata);
}
public static String get(String json, String key) {
/* No isMetadata boolean passed, presumably irrelevant. */
return JSONReader.get(json, key, false);
}
/**
* Get a value given a key and a block of JSON to search.
*/
public static String get(String json, String key, boolean isMetadata) {
key = composeKey(key, isMetadata); // Compose a key
int start = json.indexOf(key); // Index of key
if (start == -1) {
/* No match. */
return null;
}
start += key.length(); // Start of data past key
/* This JSON is pretty-printed. */
int nl = json.indexOf("\n", start);
/* Extract substring. Remove any quotation marks and commas. */
String substring = json.substring(start, nl);
return substring.replaceAll("[\",]", "");
}
/**
* Search for and return all matches.
*/
public String[] getAll(String key) {
key = composeKey(key); // Compose key
ArrayList<String> list = new ArrayList<String>(); // ArrayList to compose output array
int lastMatch = 0; // Previous match's index. Necessary for iteration through file contents.
/* While matches exist, continue. */
while ((lastMatch = this.getContents().indexOf(key, lastMatch)) != -1) {
lastMatch += key.length(); // Data starts after key.
int start = lastMatch;
/* This JSON is pretty-printed. */
int nl = this.getContents().indexOf("\n", start);
if (nl == -1) {
/* EOF. */
nl = this.getContents().length();
}
/* Extract substring. Remove any quotation marks and commas. */
String substring = this.getContents().substring(start, nl);
list.add(substring.replaceAll("[\",]", ""));
}
/* The caller doesn't need the capabilites of an ArrayList, only
those of an array. */
String[] array = new String[list.size()];
list.toArray(array);
return array;
}
/**
* @return a block of JSON associated with a font family.
* Heavily reliant on the format of popularity.json. Not
* suitable for generic JSON parsing.
*/
public String getFamily(String family) {
/* Taking advantage of the specific structure
of popularity.json. Find the index of the family
name declaration. Then, all items until the next line
starting with ' }' are included. */
String contents = this.getContents();
int start = contents.indexOf(" \"family\": \"" + family + "\",");
if (start == -1) {
/* No match. */
return null;
}
/* Restring input starting from family name declaration. */
contents = contents.substring(start);
String[] lines = contents.split("\n");
int i = 0;
/* In this format, an end block is guaranteed.
Iterate through lines until the desired level of end
block is found. */
while (!lines[i].startsWith(" }")) {
i++;
}
/* For each of the lines in the block preceding the end block,
add to output. */
String result = "";
for (int j = 0; j < i; j++) {
result += lines[j] + "\n";
}
return result;
}
/**
* Specify that this is the special pb metadata format. Almost JSON.
* See https://googlefonts.github.io/gf-guide/metadata.html. */
public void setMetadata() {
this.isMetadata = true;
}
}
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