protected List readTemplate()

in src/main/java/org/apache/commons/jexl3/internal/TemplateEngine.java [1116:1183]
63 lines of code
12 McCabe index (conditional complexity)

    protected List<Block> readTemplate(final String prefix, final Reader source) {
        final ArrayList<Block> blocks = new ArrayList<>();
        final BufferedReader reader;
        if (source instanceof BufferedReader) {
            reader = (BufferedReader) source;
        } else {
            reader = new BufferedReader(source);
        }
        final StringBuilder strb = new StringBuilder();
        BlockType type = null;
        int prefixLen;
        final Iterator<CharSequence> lines = readLines(reader);
        int lineno = 1;
        int start = 0;
        while (lines.hasNext()) {
            final CharSequence line = lines.next();
            if (line == null) {
                break;
            }
            if (type == null) {
                // determine starting type if not known yet
                prefixLen = startsWith(line, prefix);
                if (prefixLen >= 0) {
                    type = BlockType.DIRECTIVE;
                    strb.append(line.subSequence(prefixLen, line.length()));
                } else {
                    type = BlockType.VERBATIM;
                    strb.append(line.subSequence(0, line.length()));
                }
                start = lineno;
            } else if (type == BlockType.DIRECTIVE) {
                // switch to verbatim if necessary
                prefixLen = startsWith(line, prefix);
                if (prefixLen < 0) {
                    final Block directive = new Block(BlockType.DIRECTIVE, start, strb.toString());
                    strb.delete(0, Integer.MAX_VALUE);
                    blocks.add(directive);
                    type = BlockType.VERBATIM;
                    strb.append(line.subSequence(0, line.length()));
                    start = lineno;
                } else {
                    // still a directive
                    strb.append(line.subSequence(prefixLen, line.length()));
                }
            } else if (type == BlockType.VERBATIM) {
                // switch to directive if necessary
                prefixLen = startsWith(line, prefix);
                if (prefixLen >= 0) {
                    final Block verbatim = new Block(BlockType.VERBATIM, start, strb.toString());
                    strb.delete(0, Integer.MAX_VALUE);
                    blocks.add(verbatim);
                    type = BlockType.DIRECTIVE;
                    strb.append(line.subSequence(prefixLen, line.length()));
                    start = lineno;
                } else {
                    strb.append(line.subSequence(0, line.length()));
                }
            }
            lineno += 1;
        }
        // input may be null
        if (type != null && strb.length() > 0) {
            final Block block = new Block(type, start, strb.toString());
            blocks.add(block);
        }
        blocks.trimToSize();
        return blocks;
    }