74 lines
2.7 KiB
Dart
74 lines
2.7 KiB
Dart
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/// Select values in nested [List] and [Map] structures using a path that may contain wildcards.
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///
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/// The maps must always use [String] keys.
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/// The [path] is a dot-separated list of keys and indices.
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/// The wildcard "*" can be used to select all elements of a list or map.
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/// The wildcard "**" can be used to select all elements of a list or map and all elements of nested lists and maps.
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///
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/// Returns an [Iterable] of the selected values.
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///
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/// Also see [selectInJsonWithPath] for a version that returns the path to the selected values
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Iterable<T> selectInJson<T>(dynamic json, String path) {
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return selectInJsonWithPath<T>(json, path).map((e) => e.value);
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}
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Map<String, Iterable<dynamic>> selectMultipleInJson(
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dynamic json, Map<String, String> selector) {
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Map<String, Iterable<dynamic>> result = {};
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for (String key in selector.keys) {
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result[key] = selectInJsonWithPath(json, selector[key]!);
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}
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return result;
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}
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/// Select values in nested [List] and [Map] structures using a path that may contain wildcards.
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///
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/// The maps must always use [String] keys.
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/// The [path] is a dot-separated list of keys and indices.
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/// The wildcard "*" can be used to select all elements of a list or map.
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/// The wildcard "**" can be used to select all elements of a list or map and all elements of nested lists and maps.+
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///
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/// Returns an [Iterable] of the selected values and their path.
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Iterable<({T value, String path})> selectInJsonWithPath<T>(
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dynamic json, String path) sync* {
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if (path.isEmpty) {
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if (json is T) {
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yield (value: json, path: "");
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}
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return;
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}
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List<String> pathParts = path.split(".");
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String first = pathParts.removeAt(0);
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String rest = pathParts.join(".");
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addFirstToPath(({T value, String path}) element) => (
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value: element.value,
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path: element.path.isEmpty ? first : "$first.${element.path}"
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);
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if (first == "*" || first == "**") {
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String continueWithPath = first == "*" ? rest : path;
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if (json is List) {
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yield* json
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.expand((e) => selectInJsonWithPath<T>(e, continueWithPath))
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.map(addFirstToPath);
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} else if (json is Map) {
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for (String key in json.keys) {
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yield* selectInJsonWithPath<T>(json[key], continueWithPath)
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.map(addFirstToPath);
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}
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}
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} else if (json is List) {
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try {
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int index = int.parse(first);
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yield* selectInJsonWithPath<T>(json[index], rest);
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} catch (e) {
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// The first part of the path is not an index or out of bounds -> ignore
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}
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} else if (json is Map) {
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dynamic value = json[first];
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if (value != null) {
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yield* selectInJsonWithPath<T>(value, pathParts.join("."));
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}
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}
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}
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