from typing import List
from million.model.hole import Hole
from million.model.message import Message
from million.model.sequence import Sequence
import million.analyze.message_evaluation as msg_ev


def compute_sequences(messages: List[Message], accepted_max: int = 1_000_000) -> List[Sequence]:
    sequences: List[Sequence] = []
    current = Sequence(start_message=messages[0])
    
    for message in messages[1:]:
        if msg_ev.compute(message) > accepted_max: continue

        if msg_ev.compute(message) == current.end() + 1:
            current.end_message = message
        else:
            sequences.append(current)
            current = Sequence(start_message=message)

    # order the sequences by start
    sequences.sort(key=lambda s: s.start())

    merged_sequences: List[Sequence] = []
    previous = sequences[0]
    
    for sequence in sequences[1:]:
        if previous.overlaps(sequence):
            previous.merge(sequence)
        else:
            merged_sequences.append(previous)
            previous = sequence

    # Having merged the sequences once, any sequence having start = end can be removed
    return [s for s in merged_sequences if s.length() > 1]


def find_holes(messages: List[Message], accepted_max: int = 1_000_000) -> List[Hole]:
    """
    Find the holes in the conversation
    """
    merged_sequences = compute_sequences(messages, accepted_max)
    holes = []
    for i in range(1, len(merged_sequences)):
        previous_sequence = merged_sequences[i - 1]
        sequence = merged_sequences[i]
        if sequence.start() - previous_sequence.end() > 1:
            holes.append(Hole(
                start=previous_sequence.end(),
                end=sequence.start(),
                start_message=previous_sequence.end_message,
                end_message=sequence.start_message
            ))
    return holes