var _ = require('./utility');
var traverse = require('./utility/traverse');

function raw(payload, jsonBackup) {
  return [payload, _.stringify(payload, jsonBackup)];
}

function selectFrames(frames, range) {
  var len = frames.length;
  if (len > range * 2) {
    return frames.slice(0, range).concat(frames.slice(len - range));
  }
  return frames;
}

function truncateFrames(payload, jsonBackup, range) {
  range = (typeof range === 'undefined') ? 30 : range;
  var body = payload.data.body;
  var frames;
  if (body.trace_chain) {
    var chain = body.trace_chain;
    for (var i = 0; i < chain.length; i++) {
      frames = chain[i].frames;
      frames = selectFrames(frames, range);
      chain[i].frames = frames;
    }
  } else if (body.trace) {
    frames = body.trace.frames;
    frames = selectFrames(frames, range);
    body.trace.frames = frames;
  }
  return [payload, _.stringify(payload, jsonBackup)];
}

function maybeTruncateValue(len, val) {
  if (!val) {
    return val;
  }
  if (val.length > len) {
    return val.slice(0, len - 3).concat('...');
  }
  return val;
}

function truncateStrings(len, payload, jsonBackup) {
  function truncator(k, v, seen) {
    switch (_.typeName(v)) {
      case 'string':
        return maybeTruncateValue(len, v);
      case 'object':
      case 'array':
        return traverse(v, truncator, seen);
      default:
        return v;
    }
  }
  payload = traverse(payload, truncator);
  return [payload, _.stringify(payload, jsonBackup)];
}

function truncateTraceData(traceData) {
  if (traceData.exception) {
    delete traceData.exception.description;
    traceData.exception.message = maybeTruncateValue(255, traceData.exception.message);
  }
  traceData.frames = selectFrames(traceData.frames, 1);
  return traceData;
}

function minBody(payload, jsonBackup) {
  var body = payload.data.body;
  if (body.trace_chain) {
    var chain = body.trace_chain;
    for (var i = 0; i < chain.length; i++) {
      chain[i] = truncateTraceData(chain[i]);
    }
  } else if (body.trace) {
    body.trace = truncateTraceData(body.trace);
  }
  return [payload, _.stringify(payload, jsonBackup)];
}

function needsTruncation(payload, maxSize) {
  return _.maxByteSize(payload) > maxSize;
}

function truncate(payload, jsonBackup, maxSize) {
  maxSize = (typeof maxSize === 'undefined') ? (512 * 1024) : maxSize;
  var strategies = [
    raw,
    truncateFrames,
    truncateStrings.bind(null, 1024),
    truncateStrings.bind(null, 512),
    truncateStrings.bind(null, 256),
    minBody
  ];
  var strategy, results, result;

  while ((strategy = strategies.shift())) {
    results = strategy(payload, jsonBackup);
    payload = results[0];
    result = results[1];
    if (result.error || !needsTruncation(result.value, maxSize)) {
      return result;
    }
  }
  return result;
}

module.exports = {
  truncate: truncate,

  /* for testing */
  raw: raw,
  truncateFrames: truncateFrames,
  truncateStrings: truncateStrings,
  maybeTruncateValue: maybeTruncateValue
};