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define(function(require, exports, module) {
"use strict";

function throwDeltaError(delta, errorText){
    console.log("Invalid Delta:", delta);
    throw "Invalid Delta: " + errorText;
}

function positionInDocument(docLines, position) {
    return position.row    >= 0 && position.row    <  docLines.length &&
           position.column >= 0 && position.column <= docLines[position.row].length;
}

function validateDelta(docLines, delta) {
    // Validate action string.
    if (delta.action != "insert" && delta.action != "remove")
        throwDeltaError(delta, "delta.action must be 'insert' or 'remove'");
    
    // Validate lines type.
    if (!(delta.lines instanceof Array))
        throwDeltaError(delta, "delta.lines must be an Array");

    // Validate range type.
    if (!delta.start || !delta.end)
       throwDeltaError(delta, "delta.start/end must be an present");

    // Validate that the start point is contained in the document.
    var start = delta.start;
    if (!positionInDocument(docLines, delta.start))
        throwDeltaError(delta, "delta.start must be contained in document");
    
    // Validate that the end point is contained in the document (remove deltas only).
    var end = delta.end;
    if (delta.action == "remove" && !positionInDocument(docLines, end))
        throwDeltaError(delta, "delta.end must contained in document for 'remove' actions");
    
    // Validate that the .range size matches the .lines size.
    var numRangeRows = end.row - start.row;
    var numRangeLastLineChars = (end.column - (numRangeRows == 0 ? start.column : 0));
    if (numRangeRows != delta.lines.length - 1 || delta.lines[numRangeRows].length != numRangeLastLineChars)
        throwDeltaError(delta, "delta.range must match delta lines");
}

exports.applyDelta = function(docLines, delta, doNotValidate) {
    // disabled validation since it breaks autocompletion popup
    // if (!doNotValidate)
    //    validateDelta(docLines, delta);
    
    var row = delta.start.row;
    var startColumn = delta.start.column;
    var line = docLines[row] || "";
    switch (delta.action) {
        case "insert":
            var lines = delta.lines;
            if (lines.length === 1) {
                docLines[row] = line.substring(0, startColumn) + delta.lines[0] + line.substring(startColumn);
            } else {
                var args = [row, 1].concat(delta.lines);
                docLines.splice.apply(docLines, args);
                docLines[row] = line.substring(0, startColumn) + docLines[row];
                docLines[row + delta.lines.length - 1] += line.substring(startColumn);
            }
            break;
        case "remove":
            var endColumn = delta.end.column;
            var endRow = delta.end.row;
            if (row === endRow) {
                docLines[row] = line.substring(0, startColumn) + line.substring(endColumn);
            } else {
                docLines.splice(
                    row, endRow - row + 1,
                    line.substring(0, startColumn) + docLines[endRow].substring(endColumn)
                );
            }
            break;
    }
};
});