pragma solidity ^0.4.9;

contract HeadersRelay {
    mapping(uint=>uint) public merklesOfHeaders;
    uint lastRelayedBlock;

    function HeadersRelay() {
        lastRelayedBlock = 1;
    }

    function relayExpensive() {
        uint firstBlock = block.number - 129;
        for( uint index = 0 ; index < 128 ; index++ ) {
            merklesOfHeaders[index] = block.blockhash(firstBlock + index);;
        }
    }

    function relay() {
        // just test 128 blocks relay
        bytes32[128] memory scratchpad;
        uint firstBlock = block.number - 129;
        uint index;

        for( index = 0 ; index < 128 ; index++ ) {
            scratchpad[index] = block.blockhash(firstBlock + index);
        }

        uint arraySize = 128;
        while( arraySize > 1 ) {
            uint halfSize = arraySize / 2;
            for( index = 0 ; index < halfSize ; index++ ) {
                scratchpad[index] = sha3(scratchpad[2*index], scratchpad[2*index+1]);
            }

            arraySize = arraySize / 2;
        }

        merklesOfHeaders[firstBlock] = uint(scratchpad[0]);
        lastRelayedBlock = firstBlock + 128;
    }


}