# A poll with a fixed list of options and registered voters.
# One registered address = one vote. Results are public at any time.
contract Poll

const MAX_OPTIONS: int = 16
const MAX_VOTERS_PER_CALL: int = 50

state creator: address
state question: text
state options: list[text]
state tally: list[int]
state registered: map[address, bool]
state voted: map[address, bool]
state voters: int
state votes_cast: int
state closes_at: int

event VoterAdded(voter: address)
event Voted(voter: address, option: int)

init(poll_question: text, choices: list[text], duration_blocks: int):
    let size: int = len(poll_question)
    require size >= 1 and size <= 200, "question must have 1 to 200 bytes"
    require len(choices) >= 2 and len(choices) <= MAX_OPTIONS, "a poll needs 2 to 16 options"
    require duration_blocks >= 1, "duration must be at least 1 block"
    creator = caller
    question = poll_question
    closes_at = height + duration_blocks
    for choice in choices:
        require len(choice) >= 1 and len(choice) <= 64, "each option must have 1 to 64 bytes"
        options.push(choice)
        tally.push(0)

action add_voters(who: list[address]):
    require caller == creator, "only the creator registers voters"
    require height <= closes_at, "voting is closed"
    require len(who) <= MAX_VOTERS_PER_CALL, "at most 50 voters per call"
    for v in who:
        if not registered.has(v):
            registered[v] = true
            voters += 1
            emit VoterAdded(v)

action vote(option: int):
    require height <= closes_at, "voting is closed"
    require registered.has(caller), "you are not a registered voter"
    require not voted.has(caller), "you already voted"
    require option >= 0 and option < len(options), "unknown option"
    voted[caller] = true
    tally[option] += 1
    votes_cast += 1
    emit Voted(caller, option)

view results() -> list[int]:
    let out: list[int] = []
    for count in tally:
        out.push(count)
    return out

view option_name(index: int) -> text:
    return options[index]

view turnout() -> list[int]:
    return [votes_cast, voters]

view winner() -> text:
    require height > closes_at, "voting is still open"
    let best: int = 0
    let tie: bool = false
    for i in range(1, len(tally)):
        if tally[i] > tally[best]:
            best = i
            tie = false
        elif tally[i] == tally[best]:
            tie = true
    if tie:
        return "tie"
    return options[best]