function patch_fromText()

in src/client/common/editor.ts [273:351]
62 lines of code
15 McCabe index (conditional complexity)

function patch_fromText(textline: string): Patch[] {
    const patches: Patch[] = [];
    if (!textline) {
        return patches;
    }
    // Start Modification by Don Jayamanne 24/06/2016 Support for CRLF
    const text = textline.split(/[\r\n]/);
    // End Modification
    let textPointer = 0;
    const patchHeader = /^@@ -(\d+),?(\d*) \+(\d+),?(\d*) @@$/;
    while (textPointer < text.length) {
        const m = text[textPointer].match(patchHeader);
        if (!m) {
            throw new Error(`Invalid patch string: ${text[textPointer]}`);
        }

        const patch = new (<any>diff_match_patch).patch_obj();
        patches.push(patch);
        patch.start1 = parseInt(m[1], 10);
        if (m[2] === '') {
            patch.start1 -= 1;
            patch.length1 = 1;
        } else if (m[2] === '0') {
            patch.length1 = 0;
        } else {
            patch.start1 -= 1;
            patch.length1 = parseInt(m[2], 10);
        }

        patch.start2 = parseInt(m[3], 10);
        if (m[4] === '') {
            patch.start2 -= 1;
            patch.length2 = 1;
        } else if (m[4] === '0') {
            patch.length2 = 0;
        } else {
            patch.start2 -= 1;
            patch.length2 = parseInt(m[4], 10);
        }
        textPointer += 1;

        const dmp = require('diff-match-patch') as typeof import('diff-match-patch');

        while (textPointer < text.length) {
            const sign = text[textPointer].charAt(0);
            let line: string;
            try {
                //var line = decodeURI(text[textPointer].substring(1));
                // For some reason the patch generated by python files don't encode any characters
                // And this patch module (code from Google) is expecting the text to be encoded!!
                // Temporary solution, disable decoding
                // Issue #188
                line = text[textPointer].substring(1);
            } catch (ex) {
                // Malformed URI sequence.
                throw new Error('Illegal escape in patch_fromText');
            }
            if (sign === '-') {
                // Deletion.
                patch.diffs.push([dmp.DIFF_DELETE, line]);
            } else if (sign === '+') {
                // Insertion.
                patch.diffs.push([dmp.DIFF_INSERT, line]);
            } else if (sign === ' ') {
                // Minor equality.
                patch.diffs.push([dmp.DIFF_EQUAL, line]);
            } else if (sign === '@') {
                // Start of next patch.
                break;
            } else if (sign === '') {
                // Blank line?  Whatever.
            } else {
                throw new Error(`Invalid patch mode '${sign}' in: ${line}`);
            }
            textPointer += 1;
        }
    }
    return patches;
}