'use strict';

function jsonDeepClone(target) {
  return JSON.parse(
    JSON.stringify(target)
  );
}
/*
init() should return an object with: {
  save: function -> undefined - changes to in memory representation should be persisted
  This could be considered the equivalent of committing a transaction to the database.
  primaryNameservers: {
    list: function -> list nameservers
  },
  zones: {
    list: function -> list zones,
    find: function -> read zone by ???,
    create:
    update:
    delete:
  },
  records: {
    list: function -> list records,
    find: function -> read record by ???,
    create:
    update:
    delete:
  }
}

All lists will be a deep copy of the data actually stored.
 */

module.exports = function init (opts) {
  // opts = { filepath };

  var db = require(opts.filepath);
  var stat = require('fs').statSync(opts.filepath);
  var crypto = require('crypto');
  //
  // Manual Migration
  //

  // Convert the primary nameservers from strings to objects with names and IDs.
  db.primaryNameservers.forEach(function (ns, i, arr) {
    if ('string' === typeof ns) {
      ns = { name: ns };
      arr[i] = ns;
    }
    if (!ns.id) {
      ns.id = crypto.randomBytes(16).toString('hex');
    }
  });

  // Convert domains to zones and ensure that they have proper IDs and timestamps
  db.zones = db.zones || [];
  if (db.domains) {
    db.zones = db.zones.concat(db.domains);
  }
  db.zones.forEach(function (zone) {
    if (!zone.name) {
      zone.name = zone.id;
      zone.id = null;
    }
    if (!zone.id) {
      zone.id = crypto.randomBytes(16).toString('hex');
    }
    if (!zone.createdAt) { zone.createdAt = stat.mtime.valueOf(); }
    if (!zone.updatedAt) { zone.updatedAt = stat.mtime.valueOf(); }
  });

  // Records belong to zones, but they (currently) refer to them by a zone property.
  // NOTE/TODO: This may pose problems where the whole list of records is not easily
  // filtered / kept in memory / indexed and/or retrieved by zone. Traditionally,
  // records are stored "within a zone" in a zone file. We may wish to have the
  // DB API behave more traditionally, even though some stores (like a SQL database
  // table) might actually store the zone as a property of a record as we currently do.
  db.records.forEach(function (record) {
    if (!record.id) {
      record.id = crypto.randomBytes(16).toString('hex');
    }
  });

  // Write the migrated data
  require('fs').writeFileSync(opts.filepath, JSON.stringify(db, null, 2));
  //
  // End Migration
  //

  var save = function save (cb) {
    if (save._saving) {
      console.log('make pending');
      save._pending.push(cb);
      return;
    }

    save._saving = true;
    // TODO: replace with something not destructive to original non-json data
    require('fs').writeFile(opts.filepath, JSON.stringify(db, null, 2), function (err) {
      console.log('done writing');
      var pending = save._pending.splice(0);
      save._saving = false;
      cb(err);
      if (!pending.length) {
        return;
      }
      save(function (err) {
        console.log('double save');
        pending.forEach(function (cb) { cb(err); });
      });
    });
  };
  save._pending = [];

  var dbApi = {
    save: function () {
      // hide _pending and _saving from callers
      var args = [].slice.call(arguments);
      return save.apply(null, args);
    },
    // primaryNameservers really isn't editable - it's literally the list of FQDN's
    // that this database is replicated to in a multi-master fashion.
    //
    // However, lib/store/index.js does plenty to update these records in support
    // of the SOA records that are built from them (as does this file in the "migration"
    // section). I'm toying with the idea of not storing them seperately or creating the
    // SOA records somewhat immediately.
    primaryNameservers: {
      list: function listNameservers() {
        return jsonDeepClone(db.primaryNameservers);
      }
    },
    zones: {
      list: function listZones() {
        return jsonDeepClone(db.zones);
      },
      find: function getZone(predicate, cb) {
        var found;
        db.zones.some(function (z) {
          if (z.id && predicate.id === z.id) { found = z; return true; }
          if (z.name && predicate.name === z.name) { found = z; return true; }
        });
        if (!found) {
          cb(null, null);
          return;
        }
        cb(null, jsonDeepClone(found));
        return;
      },
      create: function() {},
      update: function() {},
      delete: function() {}
    },
    records: {
      list: function listRecords() {
        return jsonDeepClone(db.records);
      },
      find: function getRecord(predicate, cb) {
      },
      create: function() {},
      update: function() {},
      delete: function() {}
    }
  };

  return dbApi;
};