/*

Copyright 2011, Google Inc.
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modification, are permitted provided that the following conditions are
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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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contributors may be used to endorse or promote products derived from
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,           
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*/

package com.google.refine.pcaxis;

import java.io.IOException;
import java.io.LineNumberReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import com.google.refine.importers.TabularImportingParserBase.TableDataReader;

public class PCAxisTableDataReader implements TableDataReader {
    final private static class Dimension {
        String name;
        List<String> values;
        int next;
    }
    
    final private LineNumberReader _lnReader;
    final private List<Exception> exceptions;
    
    String _line = null;
    List<Dimension> _dimensions = null;
    
    public PCAxisTableDataReader(LineNumberReader lnReader, List<Exception> exceptions) {
        this._lnReader = lnReader;
        this.exceptions = exceptions;
    }
    
    @Override
    public List<Object> getNextRowOfCells() throws IOException {
        if (_line == null) {
            _line = _lnReader.readLine();
        }
        if (_line == null) {
            return null;
        }
        
        if (_dimensions == null) {
            return parseMetadataPrologueForColumnNames();
        } else {
            return parseForNextDataRow();
        }
    }
    
    private List<Object> parseMetadataPrologueForColumnNames() throws IOException {
        _dimensions = new LinkedList<Dimension>();
        
        List<String> dimensionNames = new ArrayList<String>();
        while (_line != null) {
            int equal = _line.indexOf('=');
            if (equal < 0 || _line.startsWith("DATA=")) {
                break;
            }
            
            // Save the line in case parseValues() changes it.
            String savedLine = _line;
            
            List<String> values = parseMetadataValues(equal + 1, exceptions);
            
            if (savedLine.startsWith("VALUES(\"")) {
                Dimension dimension = new Dimension();
                dimension.name = savedLine.substring(8, equal - 2);
                dimension.values = values;
                _dimensions.add(dimension);
            } else if (savedLine.startsWith("STUB=")) {
                dimensionNames.addAll(0, values);
            } else if (savedLine.startsWith("HEADING=")) {
                dimensionNames.addAll(values);
            }
            _line = _lnReader.readLine();
        }
        
        final Map<String, Integer> dimensionNameToOrder = new HashMap<String, Integer>();
        for (int i = 0; i < dimensionNames.size(); i++) {
            dimensionNameToOrder.put(dimensionNames.get(i), dimensionNames.size() - i - 1);
        }
        
        Collections.sort(_dimensions, new Comparator<Dimension>() {
            @Override
            public int compare(Dimension d0, Dimension d1) {
                return dimensionNameToOrder.get(d0.name)
                    .compareTo(dimensionNameToOrder.get(d1.name));
            }
        });
        
        List<Object> columnNames = new LinkedList<Object>();
        if (_dimensions.size() > 0) {
            for (int i = _dimensions.size() - 1; i > 0; i--) {
                Dimension d = _dimensions.get(i);
                columnNames.add(d.name);
            }
            columnNames.addAll(_dimensions.get(0).values);
        }
        return columnNames;
    }
    
    private List<String> parseMetadataValues(int start, List<Exception> _exceptions) throws IOException {
        List<String> values = new ArrayList<String>();
        outer:while (_line != null && start < _line.length()) {
            char c = _line.charAt(start);
            if (c == '"') {
                // A string
                StringBuffer sb = new StringBuffer();
                inner:while (_line != null && start < _line.length()) {
                    int close = _line.indexOf('"', start + 1);
                    if (close < 0) {
                        // Exceptional case of missing closing "
                        _exceptions.add(new Exception(
                            "Missing closing quotation mark on line " + _lnReader.getLineNumber()));
                        
                        sb.append(_line.substring(start + 1));
                        values.add(sb.toString());
                        break outer;
                    } else {
                        sb.append(_line.substring(start + 1, close));
                        if (close == _line.length() - 1) {
                            // String value continues on next line
                            _line = _lnReader.readLine();
                            start = 0;
                            if (_line != null && _line.length() > 0) {
                                c = _line.charAt(0);
                                if (c == '"') {
                                    continue inner;
                                }
                            }
                            break;
                        } else {
                            start = close + 1;
                            break;
                        }
                    }
                }
                values.add(sb.toString());
            } else {
                // A number or identifier
                int comma = customIndexOf(_line, ',', start + 1);
                int semicolon = customIndexOf(_line, ';', start + 1);
                int space = customIndexOf(_line, ' ', start + 1);
                int end = Math.min(comma, Math.min(semicolon, space));
                values.add(_line.substring(start, end));
                start = end;
            }
            
            if (start == _line.length()) {
                // End of line but no ;. Continue onto next line.
                _line = _lnReader.readLine();
                start = 0;
            } else {
                c = _line.charAt(start);
                if (c == ';' || c == ')') {
                    break;
                } else if (c == ',' || c == ' ' || c == '-') {
                    start++;
                    if (start == _line.length()) {
                        _line = _lnReader.readLine();
                        start = 0;
                    }
                } else {
                    // Exceptional case.
                    _exceptions.add(new Exception(
                        "Unrecognized character " + c + " on line " + _lnReader.getLineNumber()));
                    break;
                }
            }
        }
        return values;
    }
    
    private List<Object> parseForNextDataRow() throws IOException {
        List<Object> cells = getNextBatchOfDataValues(_dimensions.get(0).values.size());
        if (cells.size() == 0) {
            return null;
        }
        
        if (_dimensions.size() > 0) {
            for (int i = 1; i < _dimensions.size(); i++) {
                Dimension d = _dimensions.get(i);
                if (d.next == d.values.size()) {
                    d.next = 0;
                    if (i < _dimensions.size() - 1) {
                        _dimensions.get(i + 1).next++;
                    }
                }
                cells.add(0, d.values.get(d.next));
                if (i == 1) {
                    d.next++;
                }
            }
        }
        
        return cells;
    }
    
    private List<Object> getNextBatchOfDataValues(int expectedCount) throws IOException {
        List<Object> cells = new LinkedList<Object>();
        
        int start = _line.startsWith("DATA=") ? 5 : 0;
        while (_line != null) {
            int end = Math.min(
                customIndexOf(_line, ';', start),
                Math.min(
                    customIndexOf(_line, ' ', start),
                    customIndexOf(_line, '\t', start)));
            
            if (end > start) {
                cells.add(_line.substring(start, end));
            }
            
            while (end < _line.length()) {
                if (Character.isWhitespace(_line.charAt(end))) {
                    end++;
                } else {
                    break;
                }
            }
            if (end == _line.length()) {
                _line = _lnReader.readLine();
                start = 0;
            } else if (_line.charAt(end) == ';') {
                _line = _lnReader.readLine();
                break;
            } else {
                start = end;
            }
            
            if (cells.size() == expectedCount) {
                _line = _line.substring(start);
                break;
            }
        }
        return cells;
    }
    
    static private int customIndexOf(String s, char c, int start) {
        int i = s.indexOf(c, start);
        return i < 0 ? s.length() : i;
    }
}