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package com.box.sdk;

import com.eclipsesource.json.Json;
import com.eclipsesource.json.JsonArray;
import com.eclipsesource.json.JsonObject;
import com.eclipsesource.json.JsonValue;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Iterator;
import java.util.NoSuchElementException;

class JsonIterator {
    private final BoxAPIConnection api;
    private final URL url;
    private PagingParameters pagingParameters;
    private boolean hasMorePages;
    private Iterator currentPage;
    private JsonObject nextJsonObject;
    private Filter filter;

    JsonIterator(BoxAPIConnection api, URL url, PagingParameters pagingParameters) {
        this.api = api;
        this.url = url;
        this.pagingParameters = pagingParameters;
    }

    public boolean hasNext() {
        if (this.nextJsonObject == null) {
            this.nextJsonObject = this.loadNextJsonObject();
        }

        return this.nextJsonObject != null;
    }

    public JsonObject next() {
        if (this.nextJsonObject == null) {
            this.nextJsonObject = this.loadNextJsonObject();
        }

        if (this.nextJsonObject == null) {
            throw new NoSuchElementException();
        }

        JsonObject next = this.nextJsonObject;
        this.nextJsonObject = null;
        return next;
    }

    public void remove() {
        throw new UnsupportedOperationException();
    }

    public void setFilter(Filter filter) {
        this.filter = filter;
    }

    private void loadNextPage() {
        QueryStringBuilder builder = pagingParameters.asQueryStringBuilder();

        URL url;
        try {
            url = builder.addToURL(this.url);
        } catch (MalformedURLException e) {
            throw new BoxAPIException("Couldn't append a query string to the provided URL.");
        }

        BoxJSONRequest request = new BoxJSONRequest(this.api, url, "GET");
        try (BoxJSONResponse response = request.send()) {
            String json = response.getJSON();

            JsonObject responseObject = Json.parse(json).asObject();

            if (pagingParameters.isMarkerBasedPaging()) {
                continueAsMarkerBasedPaging(responseObject);
            } else {
                continueAsOffsetBasedPaging(responseObject);
            }

            JsonArray jsonArray = responseObject.get("entries").asArray();
            this.currentPage = jsonArray.iterator();
        }
    }

    private void continueAsOffsetBasedPaging(JsonObject response) {
        try {
            long offset = response.get("offset").asLong();
            long totalCount = response.get("total_count").asLong();
            hasMorePages = offset + pagingParameters.getLimit() < totalCount;
            this.pagingParameters = pagingParameters.nextOffset(offset);
        } catch (NullPointerException e) {
            hasMorePages = false;
        }
    }

    private void continueAsMarkerBasedPaging(JsonObject response) {
        String nextMarker = response.getString("next_marker", null);
        this.hasMorePages = nextMarker != null && nextMarker.length() > 0;
        this.pagingParameters = pagingParameters.nextMarker(nextMarker);
    }

    private JsonObject loadNextJsonObject() {
        if (this.currentPage == null) {
            this.loadNextPage();
        }

        while (this.currentPage.hasNext() || this.hasMorePages) {
            while (this.currentPage.hasNext()) {
                JsonObject jsonObject = this.currentPage.next().asObject();
                if (this.filter == null || this.filter.shouldInclude(jsonObject)) {
                    return jsonObject;
                }
            }

            if (this.hasMorePages) {
                this.loadNextPage();
            }
        }

        return null;
    }
}