pantoninho/file-interpolator

var stream = require('./stream');
var matchFinder = require('./match-finder');

module.exports = function(layoutFile, transforms, outputFile) {

    var inputStream, outputStream, interpolations, markers, partialMatch;

    inputStream = stream.fromFile(layoutFile);
    outputStream = stream.toFile(outputFile);

    markers = transforms.map(function(t) {
        return t.replace;
    });

    interpolations = [];

    return inputStream.read(function(data) {

        var matches, lastMatch;

        if (partialMatch) {
            data = partialMatch + data;
            partialMatch = '';
        }

        matches = prepareMatches(matchFinder(data, markers), transforms);
        lastMatch = matches[matches.length - 1];

        if (lastMatch.partial) {
            partialMatch = data.substring(lastMatch.at);
            data = data.substring(0, lastMatch.at);
            matches = matches.slice(0, matches.length - 1);
        }

        interpolations = interpolations.concat(stream.interpolator(data, matches));

    }).then(function() {

        var next = outputFile ? stream.utils.pipe : stream.utils.dump;
        return next(interpolations, outputStream);

    }).then(function(output) {

        return output;
    });
};

function prepareMatches(matches, transforms) {

    return matches.map(function(match) {

        var transform, content;

        transform = transforms.find(function(transform) {
            return match.marker === transform.replace;
        });

        if (transform.with || transform.with === '') {
            content = stream.fromString(transform.with);
        }

        if (transform.withFile) {
            content = stream.fromFile(transform.withFile);
        }

        return {
            marker: match.marker,
            at: match.at,
            stream: content,
            partial: match.partial
        };
    });
}