this.screenToDocumentPosition = function()

in lib/ace/edit_session.js [2116:2202]
76 lines of code
24 McCabe index (conditional complexity)

    this.screenToDocumentPosition = function(screenRow, screenColumn, offsetX) {
        if (screenRow < 0)
            return {row: 0, column: 0};

        var line;
        var docRow = 0;
        var docColumn = 0;
        var column;
        var row = 0;
        var rowLength = 0;

        var rowCache = this.$screenRowCache;
        var i = this.$getRowCacheIndex(rowCache, screenRow);
        var l = rowCache.length;
        if (l && i >= 0) {
            var row = rowCache[i];
            var docRow = this.$docRowCache[i];
            var doCache = screenRow > rowCache[l - 1];
        } else {
            var doCache = !l;
        }

        var maxRow = this.getLength() - 1;
        var foldLine = this.getNextFoldLine(docRow);
        var foldStart = foldLine ? foldLine.start.row : Infinity;

        while (row <= screenRow) {
            rowLength = this.getRowLength(docRow);
            if (row + rowLength > screenRow || docRow >= maxRow) {
                break;
            } else {
                row += rowLength;
                docRow++;
                if (docRow > foldStart) {
                    docRow = foldLine.end.row+1;
                    foldLine = this.getNextFoldLine(docRow, foldLine);
                    foldStart = foldLine ? foldLine.start.row : Infinity;
                }
            }

            if (doCache) {
                this.$docRowCache.push(docRow);
                this.$screenRowCache.push(row);
            }
        }

        if (foldLine && foldLine.start.row <= docRow) {
            line = this.getFoldDisplayLine(foldLine);
            docRow = foldLine.start.row;
        } else if (row + rowLength <= screenRow || docRow > maxRow) {
            // clip at the end of the document
            return {
                row: maxRow,
                column: this.getLine(maxRow).length
            };
        } else {
            line = this.getLine(docRow);
            foldLine = null;
        }
        var wrapIndent = 0, splitIndex = Math.floor(screenRow - row);
        if (this.$useWrapMode) {
            var splits = this.$wrapData[docRow];
            if (splits) {
                column = splits[splitIndex];
                if(splitIndex > 0 && splits.length) {
                    wrapIndent = splits.indent;
                    docColumn = splits[splitIndex - 1] || splits[splits.length - 1];
                    line = line.substring(docColumn);
                }
            }
        }

        if (offsetX !== undefined && this.$bidiHandler.isBidiRow(row + splitIndex, docRow, splitIndex))
            screenColumn = this.$bidiHandler.offsetToCol(offsetX);

        docColumn += this.$getStringScreenWidth(line, screenColumn - wrapIndent)[1];

        // We remove one character at the end so that the docColumn
        // position returned is not associated to the next row on the screen.
        if (this.$useWrapMode && docColumn >= column)
            docColumn = column - 1;

        if (foldLine)
            return foldLine.idxToPosition(docColumn);

        return {row: docRow, column: docColumn};
    };