// Copyright (c) 2017 Pieter Wuille
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

var bech32_ecc = require('./bech32_ecc');

module.exports = {
  check: check
};

function convertbits (data, frombits, tobits, pad) {
  var acc = 0;
  var bits = 0;
  var ret = [];
  var maxv = (1 << tobits) - 1;
  for (var p = 0; p < data.length; ++p) {
    var value = data[p];
    if (value < 0 || (value >> frombits) !== 0) {
      return null;
    }
    acc = (acc << frombits) | value;
    bits += frombits;
    while (bits >= tobits) {
      bits -= tobits;
      ret.push((acc >> bits) & maxv);
    }
  }
  if (pad) {
    if (bits > 0) {
      ret.push((acc << (tobits - bits)) & maxv);
    }
  } else if (bits >= frombits || ((acc << (tobits - bits)) & maxv)) {
    return null;
  }
  return ret;
}

function check (addr, validHrp) {
  if (addr.length < 14) {
    return {error:"Too short", pos:null};
  }
  if (addr.length > 74) {
    return {error:"Too long", pos:null};
  }
  eposs = []
  for (var encname in bech32_ecc.encodings) {
    const encoding = bech32_ecc.encodings[encname];
    var dec = bech32_ecc.check(addr, validHrp, encoding);
    if ("data_pattern" in dec) {
      if (dec.data_pattern !== null) {
        const numbytes = ((dec.data_pattern.length - 6 - 1) * 5) >> 3;
        if (dec.data_pattern.length - 6 - 1 != ((numbytes * 8 + 4) / 5|0)) continue;
        if (dec.data_pattern[0] == 0 && encoding != bech32_ecc.encodings.BECH32) continue;
        if (dec.data_pattern[0] > 0 && dec.data_pattern[0] <= 16 && encoding != bech32_ecc.encodings.BECH32M) continue;
        if (dec.data_pattern[0] > 16) continue;
        if (dec.data_pattern[0] == 0 && numbytes != 20 && numbytes != 32) continue;
        var epos = [];
        for (var i = 0; i < dec.data_pattern.length; ++i) {
          if (dec.data_pattern[i] == -1) {
            epos.push(addr.length - dec.data_pattern.length + i);
          }
        }
        eposs.push(epos);
      }
      continue;
    }
    if (dec.error !== null) {
      return {error:dec.error, pos:dec.pos};
    }
    var res = convertbits(dec.data.slice(1), 5, 8, false);
    if (res === null) {
      return {error:"Padding error", pos:[addr.length - 6]};
    }
    if (res.length < 2 || res.length > 40) {
      return {error:"Invalid witness program length", pos:null};
    }
    if (dec.data[0] > 16) {
      return {error:"Invalid witness version", pos:[dec.hrp.length + 1]};
    }
    if (dec.data[0] == 0 && encoding != bech32_ecc.encodings.BECH32) {
      return {error:"Bech32 must be used for witness v0 programs", pos:null};
    }
    if (dec.data[0] != 0 && encoding != bech32_ecc.encodings.BECH32M) {
      return {error:"Bech32m must be used for witness v1+ programs", pos:null};
    }
    if (dec.data[0] === 0 && res.length !== 20 && res.length !== 32) {
      return {error:"Invalid witness program length for v0", pos:null};
    }
    return {error:null, version:dec.data[0], program:res};
  }
  if (eposs.length == 1) {
    return {error:"Checksum error", pos:eposs[0]};
  }
  if (eposs.length > 1) {
    eposs.sort(function (a,b) { return a.length - b.length; });
    if (eposs[0].length < eposs[1].length) {
      return {error:"Checksum error", pos:eposs[0]};
    }
  }
  return {error:"Checksum error", pos:null};
}