import bisect


class ReplayController:

    def __init__(self, journal):

        self.journal = journal
        self.index = 0
        self.playing = False

        # pre-sorted events for deterministic replay
        self.timeline = sorted(
            journal.events,
            key=lambda e: e["ts"]
        )

    # -------------------------
    # CURRENT EVENT
    # -------------------------
    def current(self):

        if 0 <= self.index < len(self.timeline):
            return self.timeline[self.index]

        return None

    # -------------------------
    # STEP FORWARD
    # -------------------------
    def step(self):

        if self.index < len(self.timeline) - 1:
            self.index += 1

        return self.current()

    # -------------------------
    # STEP BACKWARD
    # -------------------------
    def back(self):

        if self.index > 0:
            self.index -= 1

        return self.current()

    # -------------------------
    # SEEK BY TIMESTAMP
    # -------------------------
    def seek(self, timestamp):

        times = [e["ts"] for e in self.timeline]

        self.index = bisect.bisect_left(times, timestamp)

        return self.current()

    # -------------------------
    # RESET
    # -------------------------
    def reset(self):

        self.index = 0

        return self.current()

    # -------------------------
    # PLAY (ITERATOR MODE)
    # -------------------------
    def play(self):

        for i in range(self.index, len(self.timeline)):
            self.index = i
            yield self.timeline[i]