com.tvd12.ezyhttp.server.graphql.GraphQLSchemaParser Maven / Gradle / Ivy

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package com.tvd12.ezyhttp.server.graphql;

import java.util.Stack;

public final class GraphQLSchemaParser {

    @SuppressWarnings("MethodLength")
    public GraphQLSchema parseQuery(String queryToParse) {
        String query = standardize(queryToParse);

        Stack stack = new Stack<>();
        GraphQLSchema.Builder schemaBuilder = GraphQLSchema.builder();

        int nameLength = 0;
        char[] nameBuffer = new char[128];
        for (int i = 0; i < query.length(); ++i) {
            char ch = query.charAt(i);
            if (ch == '{') {
                if (stack.isEmpty()) {
                    GraphQLQueryDefinition.Builder queryBuilder =
                        GraphQLQueryDefinition.builder();
                    stack.add(queryBuilder);
                    continue;
                }

                GraphQLField.Builder builder = stack.peek();
                if (nameLength > 0) {
                    builder.name(String.copyValueOf(nameBuffer, 0, nameLength));
                    nameLength = 0;
                }
                GraphQLField.Builder childBuilder = GraphQLField.builder();
                stack.add(childBuilder);
                continue;
            }

            if (ch == '}') {
                if (stack.isEmpty()) {
                    continue;
                }
                if (stack.size() == 1) {
                    GraphQLField.Builder item = stack.pop();
                    if (nameLength > 0) {
                        item.name(String.copyValueOf(nameBuffer, 0, nameLength));
                        nameLength = 0;
                    }
                    schemaBuilder.addQueryDefinition((GraphQLQueryDefinition) item.build());
                    continue;
                }

                GraphQLField.Builder childBuilder = stack.pop();
                if (nameLength > 0) {
                    childBuilder.name(String.copyValueOf(nameBuffer, 0, nameLength));
                    nameLength = 0;
                }

                GraphQLField.Builder parentBuilder = stack.peek();
                parentBuilder.addField(childBuilder.build());

                if (stack.size() == 1) {
                    GraphQLField.Builder item = stack.pop();
                    schemaBuilder.addQueryDefinition((GraphQLQueryDefinition) item.build());
                }
            } else if (ch == ' ') { // ',' '\t' '\n' '+' have been removed
                if (stack.isEmpty()) {
                    GraphQLQueryDefinition.Builder queryBuilder = GraphQLQueryDefinition.builder();
                    stack.add(queryBuilder);
                    nameLength = 0;
                    continue;
                }

                if (stack.size() == 1) {
                    GraphQLField.Builder item = stack.pop();
                    item.name(String.copyValueOf(nameBuffer, 0, nameLength));
                    nameLength = 0;
                    schemaBuilder.addQueryDefinition((GraphQLQueryDefinition) item.build());

                    GraphQLQueryDefinition.Builder queryBuilder = GraphQLQueryDefinition.builder();
                    stack.add(queryBuilder);
                    continue;
                }

                GraphQLField.Builder childBuilder = stack.pop();
                if (nameLength > 0) {
                    childBuilder.name(String.copyValueOf(nameBuffer, 0, nameLength));
                    nameLength = 0;
                }

                GraphQLField.Builder parentBuilder = stack.peek();
                parentBuilder.addField(childBuilder.build());

                GraphQLField.Builder newChildBuilder = GraphQLField.builder();
                stack.add(newChildBuilder);
            } else {
                nameBuffer[nameLength++] = ch;
            }
        }
        return schemaBuilder.build();
    }

    /**
     * Remove redundant '\t', '\n', '+', ',', ' ' in query.
     *
     * @param query query in original format
     * @return standardized query
     */
    private String standardize(String query) {
        if (query == null) {
            return "";
        }
        String trimedQuery = query.trim();
        StringBuilder forwardStandard = forwardStandardize(trimedQuery);
        StringBuilder backwardStandard = backwardStandardize(forwardStandard.toString());
        return removeQueryPrefix(backwardStandard.toString());
    }

    private StringBuilder forwardStandardize(String query) {
        StringBuilder answer = new StringBuilder();
        for (int i = 0; i < query.length(); ++i) {
            char ch = query.charAt(i);
            if (ch == '{' || ch == '}') {
                answer.append(ch);
            } else if (ch == '+' || ch == ',' || ch == ' ' || ch == '\t' || ch == '\n') {
                char lastChar = answer.charAt(answer.length() - 1);
                if ((lastChar != ' ') && (lastChar != '{')) {
                    answer.append(' ');
                }
            } else {
                answer.append(ch);
            }
        }
        return answer;
    }

    private StringBuilder backwardStandardize(String query) {
        StringBuilder answer = new StringBuilder();
        for (int i = query.length() - 1; i >= 0; --i) {
            char ch = query.charAt(i);
            if (ch == '{' || ch == '}') {
                answer.insert(0, ch);
            } else if (ch == ' ') { // ',' '\t' '\n' '+' have been removed in forward pass
                char firstChar = answer.charAt(0);
                if ((firstChar != '{') && (firstChar != '}')) {
                    answer.insert(0, ' ');
                }
            } else {
                answer.insert(0, ch);
            }
        }
        return answer;
    }

    private String removeQueryPrefix(String s) {
        String prefix = "query";
        if (s.startsWith(prefix)) {
            return s.substring(prefix.length());
        }
        return s;
    }
}