const DB_RECORD_LEN = 4;
const DB_RECORDS_PER_HR = 6;
const DB_RECORDS_PER_DAY = DB_RECORDS_PER_HR*24 + 1/*summary*/;
//const DB_RECORDS_PER_MONTH = DB_RECORDS_PER_DAY*31;
const DB_HEADER_LEN = 8;
//const DB_FILE_LEN = DB_HEADER_LEN + DB_RECORDS_PER_MONTH*DB_RECORD_LEN;

function getRecordFN(d) {
  return "health-"+d.getFullYear()+"-"+(d.getMonth()+1)+".raw";
}
function getRecordIdx(d) {
  return (DB_RECORDS_PER_DAY*(d.getDate()-1)) +
         (DB_RECORDS_PER_HR*d.getHours()) +
         (0|(d.getMinutes()*DB_RECORDS_PER_HR/60));
}

// Read all records from the given month
exports.readAllRecords = function(d, cb) {
  var fn = getRecordFN(d);
  var f = require("Storage").read(fn);
  if (f===undefined) return;
  var idx = DB_HEADER_LEN;
  for (var day=0;day<31;day++) {
    for (var hr=0;hr<24;hr++) { // actually 25, see below
      for (var m=0;m<DB_RECORDS_PER_HR;m++) {
        var h = f.substr(idx, DB_RECORD_LEN);
        if (h!="\xFF\xFF\xFF\xFF") {
          cb({
            day:day+1, hr : hr, min:m*10,
            steps : (h.charCodeAt(0)<<8) | h.charCodeAt(1),
            bpm : h.charCodeAt(2),
            movement : h.charCodeAt(3)*8
          });
        }
        idx += DB_RECORD_LEN;
      }
    }
    idx += DB_RECORD_LEN; // +1 because we have an extra record with totals for the end of the day
  }
};

// Read the entire database. There is no guarantee that the months are read in order.
exports.readFullDatabase = function(cb) {
  require("Storage").list(/health-[0-9]+-[0-9]+.raw/).forEach(val => {
    console.log(val);
    var parts = val.split('-');
    var y = parseInt(parts[1]);
    var mo = parseInt(parts[2].replace('.raw', ''));

    exports.readAllRecords(new Date(y, mo, 1), (r) => {
      r.date = new Date(y, mo, r.day, r.hr, r.min);
      cb(r);
    });
  });
};

// Read all records per day, until the current time.
// There may be some records for the day of the timestamp previous to the timestamp
exports.readAllRecordsSince = function(d, cb) {
  var currentDate = new Date().getTime();
  var di = d;
  while (di.getTime() <= currentDate) {
    exports.readDay(di, (r) => {
      r.date = new Date(di.getFullYear(), di.getMonth(), di.getDate(), r.hr, r.min);
      cb(r);
    });
    di.setDate(di.getDate() + 1);
  }
};

// Read daily summaries from the given month
exports.readDailySummaries = function(d, cb) {
  /*var rec =*/ getRecordIdx(d);
  var fn = getRecordFN(d);
  var f = require("Storage").read(fn);
  if (f===undefined) return;
  var idx = DB_HEADER_LEN + (DB_RECORDS_PER_DAY-1)*DB_RECORD_LEN; // summary is at the end of each day
  for (var day=0;day<31;day++) {
    var h = f.substr(idx, DB_RECORD_LEN);
    if (h!="\xFF\xFF\xFF\xFF") {
      cb({
        day:day+1,
        steps : (h.charCodeAt(0)<<8) | h.charCodeAt(1),
        bpm : h.charCodeAt(2),
        movement : h.charCodeAt(3)*8
      });
    }
    idx += DB_RECORDS_PER_DAY*DB_RECORD_LEN;
  }
}

// Read all records from the given day
exports.readDay = function(d, cb) {
  /*var rec =*/ getRecordIdx(d);
  var fn = getRecordFN(d);
  var f = require("Storage").read(fn);
  if (f===undefined) return;
  var idx = DB_HEADER_LEN + (DB_RECORD_LEN*DB_RECORDS_PER_DAY*(d.getDate()-1));
  for (var hr=0;hr<24;hr++) {
    for (var m=0;m<DB_RECORDS_PER_HR;m++) {
      var h = f.substr(idx, DB_RECORD_LEN);
      if (h!="\xFF\xFF\xFF\xFF") {
        cb({
          hr : hr, min:m*10,
          steps : (h.charCodeAt(0)<<8) | h.charCodeAt(1),
          bpm : h.charCodeAt(2),
          movement : h.charCodeAt(3)*8
        });
      }
      idx += DB_RECORD_LEN;
    }
  }
}