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Copyright 2010, Google Inc.
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    * Redistributions of source code must retain the above copyright
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    * Redistributions in binary form must reproduce the above
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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*/

package com.google.refine.operations.column;

import static com.google.common.base.Strings.isNullOrEmpty;

import java.io.IOException;
import java.io.Serializable;
import java.net.MalformedURLException;
import java.net.URISyntaxException;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.util.concurrent.TimeUnit;

import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.StatusLine;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.entity.ContentType;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicHeader;
import org.apache.http.util.EntityUtils;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

import com.google.refine.RefineServlet;
import com.google.refine.browsing.Engine;
import com.google.refine.browsing.EngineConfig;
import com.google.refine.browsing.FilteredRows;
import com.google.refine.browsing.RowVisitor;
import com.google.refine.expr.EvalError;
import com.google.refine.expr.Evaluable;
import com.google.refine.expr.ExpressionUtils;
import com.google.refine.expr.MetaParser;
import com.google.refine.expr.WrappedCell;
import com.google.refine.history.HistoryEntry;
import com.google.refine.model.Cell;
import com.google.refine.model.Column;
import com.google.refine.model.Project;
import com.google.refine.model.Row;
import com.google.refine.model.changes.CellAtRow;
import com.google.refine.model.changes.ColumnAdditionChange;
import com.google.refine.operations.EngineDependentOperation;
import com.google.refine.operations.OnError;
import com.google.refine.process.LongRunningProcess;
import com.google.refine.process.Process;
import com.google.refine.util.ParsingUtilities;


public class ColumnAdditionByFetchingURLsOperation extends EngineDependentOperation {
    public static final class HttpHeader  {
        @JsonProperty("name")
        final public String name;
        @JsonProperty("value")
        final public String value;
        
        @JsonCreator
        public HttpHeader(
                @JsonProperty("name")
                String name,
                @JsonProperty("value")
                String value) {
            this.name = name;
            this.value = value;
        }
    }
    
    final protected String     _baseColumnName;
    final protected String     _urlExpression;
    final protected OnError    _onError;

    final protected String     _newColumnName;
    final protected int        _columnInsertIndex;
    final protected int        _delay;
    final protected boolean    _cacheResponses;
    final protected List<HttpHeader>  _httpHeadersJson;
    private Header[] httpHeaders = new Header[0];
    final private RequestConfig defaultRequestConfig;
    private HttpClientBuilder httpClientBuilder;

    @JsonCreator
    public ColumnAdditionByFetchingURLsOperation(
        @JsonProperty("engineConfig")
        EngineConfig   engineConfig,
        @JsonProperty("baseColumnName")
        String         baseColumnName,
        @JsonProperty("urlExpression")
        String         urlExpression,
        @JsonProperty("onError")
        OnError        onError,
        @JsonProperty("newColumnName")
        String         newColumnName,
        @JsonProperty("columnInsertIndex")
        int            columnInsertIndex,
        @JsonProperty("delay")
        int            delay,
        @JsonProperty("cacheResponses")
        boolean        cacheResponses,
        @JsonProperty("httpHeadersJson")
        List<HttpHeader>      httpHeadersJson
    ) {
        super(engineConfig);

        _baseColumnName = baseColumnName;
        _urlExpression = urlExpression;
        _onError = onError;

        _newColumnName = newColumnName;
        _columnInsertIndex = columnInsertIndex;

        _delay = delay;
        _cacheResponses = cacheResponses;
        _httpHeadersJson = httpHeadersJson;

        List<Header> headers = new ArrayList<Header>();
        if (_httpHeadersJson != null) {
            for (HttpHeader header : _httpHeadersJson) {
                if (!isNullOrEmpty(header.name) && !isNullOrEmpty(header.value)) {
                    headers.add(new BasicHeader(header.name, header.value));
                }
            }
        }
        httpHeaders = headers.toArray(httpHeaders);

        defaultRequestConfig = RequestConfig.custom()
                .setConnectTimeout(30 * 1000)
                .setConnectionRequestTimeout(30 * 1000)
                .setSocketTimeout(10 * 1000).build();

        // TODO: Placeholder for future Basic Auth implementation
//        CredentialsProvider credsProvider = new BasicCredentialsProvider();
//        credsProvider.setCredentials(new AuthScope(host, 443),
//                new UsernamePasswordCredentials(user, password));

        httpClientBuilder = HttpClients.custom()
                .setUserAgent(RefineServlet.getUserAgent())
                .setDefaultRequestConfig(defaultRequestConfig);
//               .setConnectionBackoffStrategy(ConnectionBackoffStrategy)
//               .setDefaultCredentialsProvider(credsProvider);
    }

    @JsonProperty("newColumnName")
    public String getNewColumnName() {
        return _newColumnName;
    }

    @JsonProperty("columnInsertIndex")
    public int getColumnInsertIndex() {
        return _columnInsertIndex;
    }
    
    @JsonProperty("baseColumnName")
    public String getBaseColumnName() {
        return _baseColumnName;
    }
    
    @JsonProperty("urlExpression")
    public String getUrlExpression() {
        return _urlExpression;
    }
    
    @JsonProperty("onError")
    public OnError getOnError() {
        return _onError;
    }
    
    @JsonProperty("delay")
    public int getDelay() {
        return _delay;
    }
    
    @JsonProperty("httpHeadersJson")
    public List<HttpHeader> getHttpHeadersJson() {
        return _httpHeadersJson;
    }
    
    @JsonProperty("cacheResponses")
    public boolean getCacheResponses() {
        return _cacheResponses;
    }

    @Override
    protected String getBriefDescription(Project project) {
        return "Create column " + _newColumnName +
            " at index " + _columnInsertIndex +
            " by fetching URLs based on column " + _baseColumnName +
            " using expression " + _urlExpression;
    }

    protected String createDescription(Column column, List<CellAtRow> cellsAtRows) {
        return "Create new column " + _newColumnName +
            ", filling " + cellsAtRows.size() +
            " rows by fetching URLs based on column " + column.getName() +
            " and formulated as " + _urlExpression;
    }


    @Override
    public Process createProcess(Project project, Properties options) throws Exception {
        Engine engine = createEngine(project);
        engine.initializeFromConfig(_engineConfig);

        Evaluable eval = MetaParser.parse(_urlExpression);

        return new ColumnAdditionByFetchingURLsProcess(
            project,
            engine,
            eval,
            getBriefDescription(null),
            _cacheResponses
        );
    }

    public class ColumnAdditionByFetchingURLsProcess extends LongRunningProcess implements Runnable {
        final protected Project       _project;
        final protected Engine        _engine;
        final protected Evaluable     _eval;
        final protected long          _historyEntryID;
        protected int                 _cellIndex;
        protected LoadingCache<String, Serializable> _urlCache;

        public ColumnAdditionByFetchingURLsProcess(
            Project project,
            Engine engine,
            Evaluable eval,
            String description,
            boolean cacheResponses
        ) {
            super(description);
            _project = project;
            _engine = engine;
            _eval = eval;
            _historyEntryID = HistoryEntry.allocateID();
            _urlCache = null;
            if (cacheResponses) {
                _urlCache = CacheBuilder.newBuilder()
                .maximumSize(2048)
                .expireAfterWrite(10, TimeUnit.MINUTES)
                .build(
                     new CacheLoader<String, Serializable>() {
                        public Serializable load(String urlString) throws Exception {
                            Serializable result = fetch(urlString);
                            try {
                                // Always sleep for the delay, no matter how long the
                                // request took. This is more responsible than substracting
                                // the time spend requesting the URL, because it naturally
                                // slows us down if the server is busy and takes a long time
                                // to reply.
                                if (_delay > 0) {
                                    Thread.sleep(_delay);
                                }
                            } catch (InterruptedException e) {
                                result = null;
                            }

                            if (result == null) {
                                // the load method should not return any null value
                                throw new Exception("null result returned by fetch");
                            }
                            return result;
                        }
                        });
            }
        }
        
        @Override
        protected Runnable getRunnable() {
            return this;
        }

        @Override
        public void run() {
            Column column = _project.columnModel.getColumnByName(_baseColumnName);
            if (column == null) {
                _project.processManager.onFailedProcess(this, new Exception("No column named " + _baseColumnName));
                return;
            }
            if (_project.columnModel.getColumnByName(_newColumnName) != null) {
                _project.processManager.onFailedProcess(this, new Exception("Another column already named " + _newColumnName));
                return;
            }

            List<CellAtRow> urls = new ArrayList<CellAtRow>(_project.rows.size());

            FilteredRows filteredRows = _engine.getAllFilteredRows();
            filteredRows.accept(_project, createRowVisitor(urls));

            int count = urls.size();
            List<CellAtRow> responseBodies = new ArrayList<CellAtRow>(count);
            int i = 0;
            for (CellAtRow urlData : urls) {
                String urlString = urlData.cell.value.toString();

                Serializable response = null;
                if (_urlCache != null) {
                    response = cachedFetch(urlString); // TODO: Why does this need a separate method?
                } else {
                    response = fetch(urlString);
                }

                if (response != null) {
                    CellAtRow cellAtRow = new CellAtRow(
                            urlData.row,
                            new Cell(response, null));

                    responseBodies.add(cellAtRow);
                }

                _progress = i++ * 100 / count;

                if (_canceled) {
                    break;
                }
            }

            if (!_canceled) {
                HistoryEntry historyEntry = new HistoryEntry(
                    _historyEntryID,
                    _project,
                    _description,
                    ColumnAdditionByFetchingURLsOperation.this,
                    new ColumnAdditionChange(
                        _newColumnName,
                        _columnInsertIndex,
                        responseBodies)
                );

                _project.history.addEntry(historyEntry);
                _project.processManager.onDoneProcess(this);
            }
        }

        Serializable cachedFetch(String urlString) {
            try {
                return  _urlCache.get(urlString);
            } catch(Exception e) {
                return null;
            }
        }

        Serializable fetch(String urlString) {
            HttpGet httpGet;

            try {
                // Use of URL constructor below is purely to get additional error checking to mimic
                // previous behavior for the tests.
                httpGet = new HttpGet(new URL(urlString).toURI());
            } catch (IllegalArgumentException | MalformedURLException | URISyntaxException e) {
                return null;
            }

            try {
                httpGet.setHeaders(httpHeaders);
                httpGet.setConfig(defaultRequestConfig);

                CloseableHttpClient httpclient = httpClientBuilder.build();

                CloseableHttpResponse response = null;
                try {
                    response = httpclient.execute(httpGet);

                    HttpEntity entity = response.getEntity();
                    if (entity == null) {
                        throw new Exception("No content found in " + httpGet.getURI().toString());
                    }

                    String encoding = null;

                    if (entity.getContentEncoding() != null) {
                        encoding = entity.getContentEncoding().getValue();
                    } else {
                        Charset charset = ContentType.getOrDefault(entity).getCharset();
                        if (charset != null) {
                            encoding = charset.name();
                        }
                    }

                    String result =  ParsingUtilities.inputStreamToString(
                            entity.getContent(), (encoding == null) || ( encoding.equalsIgnoreCase("\"UTF-8\"")) ? "UTF-8" : encoding);

                    EntityUtils.consume(entity);
                    return result;

                } catch (IOException e) {
                    String message;
                    if (response == null) {
                        message = "Unknown HTTP error " + e.getLocalizedMessage();
                    } else {
                        StatusLine status = response.getStatusLine();
                        HttpEntity errorEntity = response.getEntity();
                        String errorString = ParsingUtilities.inputStreamToString(errorEntity.getContent());
                        message = String.format("HTTP error %d : %s | %s", status.getStatusCode(),
                                status.getReasonPhrase(),
                                errorString);
                    }
                    return _onError == OnError.StoreError ? new EvalError(message) : null;
                }
            } catch (Exception e) {
                return _onError == OnError.StoreError ? new EvalError(e.getMessage()) : null;
            }
        }

        RowVisitor createRowVisitor(List<CellAtRow> cellsAtRows) {
            return new RowVisitor() {
                int              cellIndex;
                Properties       bindings;
                List<CellAtRow>  cellsAtRows;

                public RowVisitor init(List<CellAtRow> cellsAtRows) {
                    Column column = _project.columnModel.getColumnByName(_baseColumnName);

                    this.cellIndex = column.getCellIndex();
                    this.bindings = ExpressionUtils.createBindings(_project);
                    this.cellsAtRows = cellsAtRows;
                    return this;
                }

                @Override
                public void start(Project project) {
                    // nothing to do
                }

                @Override
                public void end(Project project) {
                    // nothing to do
                }

                @Override
                public boolean visit(Project project, int rowIndex, Row row) {
                    Cell cell = row.getCell(cellIndex);
                    Cell newCell = null;

                    ExpressionUtils.bind(bindings, row, rowIndex, _baseColumnName, cell);

                    Object o = _eval.evaluate(bindings);
                    if (o != null) {
                        if (o instanceof Cell) {
                            newCell = (Cell) o;
                        } else if (o instanceof WrappedCell) {
                            newCell = ((WrappedCell) o).cell;
                        } else {
                            Serializable v = ExpressionUtils.wrapStorable(o);
                            if (ExpressionUtils.isNonBlankData(v)) {
                                newCell = new Cell(v.toString(), null);
                            }
                        }
                    }

                    if (newCell != null) {
                        cellsAtRows.add(new CellAtRow(rowIndex, newCell));
                    }

                    return false;
                }
            }.init(cellsAtRows);
        }
    }
}
