var _ = require('lodash');

module.exports = function regionExtractor() {

  var nullLine = '###';
  var nullLinePattern = new RegExp(nullLine + '\n', 'g');

  // split out each fragment in {content} into a separate doc
  // a fragment is a section of text surrounded by
  //   1) In front: a comment marker followed by '#docregion' followed by an optional region name. For example:
  //        <-- #docregion foo --> for html
  //     or // #docregion foo      for js/ts
  //   2) In back: a comment marker followed by '#enddocregion'
  // Regions can be nested and any regions not 'closed' are automatically closed at the end of the doc.

  // empty enddocregion always closes last region started.
  // enddocregions with names that do no match start region tags get ignored.

  return function(content, commentPrefixes) {

    var lines = result = content.split(/\r?\n/);

    var docStack = [];
    var docMap = {};
    var doc;
    var regionNames;
    lines.forEach(function(line, ix) {
      if (isCommentLine(line, commentPrefixes)) {
        if (hasRegionTag(line)) {
          lines[ix] = nullLine;

          regionNames = getRegionNames(line);
          regionNames.forEach(function(rn) {
            doc = docMap[rn];
            if (!doc) {
              // regionName may be ''
              doc = {regionName: rn, ranges: [ { startIx: ix} ] };
              docMap[rn] = doc;
            } else {
              // only add a new range if prev range is closed
              var lastRange = doc.ranges[doc.ranges.length-1];
              if (lastRange.endIx) {
                doc.ranges.push({startIx: ix});
              }
            }
            docStack.push(doc);
          });

        } else if (hasEndRegionTag(line)) {
          lines[ix] = nullLine;
          regionNames = getEndRegionNames(line);
          regionNames.forEach(function(rn) {
            // handle endregions with no name specially.
            // They operate on the last region created.
            if (rn.length == 0) {
              if (docStack.length) {
                // update last item on the stack
                doc = docStack.pop();
                doc.ranges[doc.ranges.length - 1].endIx = ix;
              }
            } else {
              doc = docMap[rn];
              // ignore endregion if name is specified but not found.
              if (doc) {
                doc.ranges[doc.ranges.length - 1].endIx = ix;
                // remove doc from stack
                _.remove(docStack, function (item) {
                  return item.regionName === rn;
                });
              }
            }

          })
        }
      }
    });

    var docs = _.values(docMap);
    docs.forEach(function(doc) {
      var content;
      var fragLines = [];
      doc.ranges.forEach(function (range) {
        var subLines;
        if (range.endIx) {
          subLines = lines.slice(range.startIx + 1, range.endIx);
        } else {
          subLines = lines.slice(range.startIx + 1);
        }
        fragLines = fragLines.concat(subLines);
      });
      fragLines = trimLeftIndent(fragLines);
      content = fragLines.join('\n');
      // eliminate all #docregion lines
      content = content.replace(nullLinePattern, '');
      if (content.substr(-3) === nullLine) {
        content = content.substr(0, content.length-3);
      }
      doc.content = content;
    });
    return docs;
  }

};

function trimLeftIndent(lines) {
  var minIx  = 100;
  var ok = lines.every(function(line) {
    // var ix = line.search(/\S/);
    var ix = line.search(/[^ ]/);
    if (ix === 0) return false;
    if (ix === -1) return true;
    if (ix > 0) {
      minIx = Math.min(minIx, ix);
    }
    return true;
  });
  if ( (!ok) || minIx === 100) return lines;

  var result = lines.map(function(line) {
    if (line.length > minIx) {
      return line.substr(minIx);
    } else {
      // this can happen if line is all blanks and shorter than mixIx
      return line;
    }
  });
  return result;
}

function isCommentLine(line, commentPrefixes) {
  return commentPrefixes.some(function(prefix) {
    return line.trim().indexOf(prefix) == 0;
  });
}

function hasRegionTag(line) {
  return line.indexOf("#docregion") >= 0;
}

function hasEndRegionTag(line) {
  return line.indexOf("#enddocregion") >= 0;
}

function getRegionNames(line) {
  return extractRegionNames(line, /#docregion\s*(\S.*)/);
}

function getEndRegionNames(line) {
  return extractRegionNames(line, /#enddocregion\s*(\S.*)/);
}

function extractRegionNames(line, rx) {
  try {
    var names = line.match(rx)[1];
    names = names.replace(/\s*/g,'');
    // Hack for html regions that look like <!-- #docregion --> or */
    names = names.replace("-->","").replace('\*\/',"");
    names = names.split(',');
    return names;
  } catch (e) {
    return [''];
  }
}