# backend/app/core/brackets.py

import math
from typing import Optional


class Match:
    def __init__(self, match_id: int, name: str):
        self.id = match_id
        self.name = name
        self.next_win: Optional["Match"] = None
        self.next_loss: Optional["Match"] = None
        self.players: list[Optional[int]] = [None, None]
        self.is_bye: bool = False
        self.ghost_count: int = 0


class BracketGenerator:

    def __init__(self):
        self.matches_dict = {}
        self.match_counter = 1

    def generate(
        self, num_players: int, double_elimination: bool = False
    ) -> list[Match]:
        self.matches_dict = {}
        self.match_counter = 1

        size = 2 ** math.ceil(math.log2(num_players))
        seeds = self._generate_seeding_indices(num_players)

        bracket = self._create_tree_bracket(size, "WB")

        for i, match in enumerate(bracket[0]):
            match.players = [seeds[i * 2], seeds[i * 2 + 1]]

        lb_rounds = []
        if double_elimination:
            lb_rounds = self._create_strict_lb(size, bracket)

        if double_elimination:
            self._create_de_finals(bracket, lb_rounds)
        else:
            self._create_se_third_place(bracket)

        self._apply_ghost_logic(bracket[0], num_players)

        all_matches = sorted(self.matches_dict.values(), key=lambda x: x.id)
        return [m for m in all_matches if not m.is_bye]

    def _generate_seeding_indices(self, num_players: int) -> list[int]:
        p2 = 2 ** math.ceil(math.log2(num_players))
        seeds = [1]
        curr = 1
        while curr < p2:
            seeds = [x for val in seeds for x in (val, (curr * 2) + 1 - val)]
            curr *= 2
        return seeds

    def _create_tree_bracket(self, size: int, prefix: str) -> list[list[Match]]:
        rounds: list[list[Match]] = []
        current_size = size // 2
        r_num = 1

        while current_size >= 1:
            round_matches: list[Match] = []
            for _ in range(current_size):
                name = f"{prefix} Round {r_num}"
                m = Match(self.match_counter, name)
                self.matches_dict[m.id] = m
                round_matches.append(m)
                self.match_counter += 1
            rounds.append(round_matches)
            current_size //= 2
            r_num += 1

        if rounds:
            rounds[-1][0].name = "Grand Final"
        if len(rounds) > 1:
            for m in rounds[-2]:
                m.name = f"{prefix} Semifinal"

        for r in range(len(rounds) - 1):
            for i, match in enumerate(rounds[r]):
                match.next_win = rounds[r + 1][i // 2]

        return rounds

    def _create_strict_lb(
        self, size: int, wb_rounds: list[list[Match]]
    ) -> list[list[Match]]:
        lb_rounds: list[list[Match]] = []
        num_wb_rounds = len(wb_rounds)
        total_lb_rounds = (num_wb_rounds - 1) * 2

        current_lb_size = size // 4
        if current_lb_size < 1:
            current_lb_size = 1

        for r in range(1, total_lb_rounds + 1):
            if r > 2 and r % 2 != 0:
                current_lb_size //= 2

            round_matches = []
            for _ in range(current_lb_size):
                m = Match(self.match_counter, f"LB Round {r}")
                self.matches_dict[m.id] = m
                round_matches.append(m)
                self.match_counter += 1
            lb_rounds.append(round_matches)

        if lb_rounds:
            lb_rounds[-1][0].name = "Losers Final (3rd Place Match)"

        for r in range(len(lb_rounds) - 1):
            curr = lb_rounds[r]
            next_r = lb_rounds[r + 1]
            for i, match in enumerate(curr):
                if len(curr) == len(next_r):
                    match.next_win = next_r[i]
                else:
                    match.next_win = next_r[i // 2]

        for r in range(num_wb_rounds):
            wb_round = wb_rounds[r]

            if r == 0:
                lb_target_idx = 0
            else:
                lb_target_idx = (r * 2) - 1

            if lb_target_idx >= len(lb_rounds):
                break

            lb_round = lb_rounds[lb_target_idx]

            for i, wb_match in enumerate(wb_round):
                if r == 0:
                    target = lb_round[i // 2]
                else:
                    target = lb_round[i] if i < len(lb_round) else lb_round[0]

                wb_match.next_loss = target

        return lb_rounds

    def _create_se_third_place(self, wb_rounds: list[list[Match]]) -> None:
        """Creates a standalone 3rd place match for Single Elim"""
        if len(wb_rounds) < 2:
            return

        semis = wb_rounds[-2]
        third_place_match = Match(self.match_counter, "3rd Place Match")
        self.matches_dict[third_place_match.id] = third_place_match
        self.match_counter += 1

        for m in semis:
            m.next_loss = third_place_match

    def _create_de_finals(
        self, wb_rounds: list[list[Match]], lb_rounds: list[list[Match]]
    ) -> None:
        """Links Double Elim Grand Final"""
        wb_final = wb_rounds[-1][0]
        wb_final.name = "Winners Final"

        gf = Match(self.match_counter, "Grand Final")
        self.matches_dict[gf.id] = gf
        self.match_counter += 1

        wb_final.next_win = gf
        if lb_rounds:
            lb_rounds[-1][0].next_win = gf
            reset = Match(self.match_counter, "Grand Final Reset")
            self.matches_dict[reset.id] = reset
            self.match_counter += 1
            gf.next_loss = reset

    def _apply_ghost_logic(
        self, round_one_matches: list[Match], num_players: int
    ) -> None:
        """
        Injects ghosts into WB Round 1 and lets them flow recursively.
        """
        for m in round_one_matches:
            p1, p2 = m.players
            if p1 and p1 > num_players:
                self._add_ghost(m)
            if p2 and p2 > num_players:
                self._add_ghost(m)

    def _add_ghost(self, match: Match) -> None:
        """
        Recursively propagates a ghost through the bracket.
        """
        match.ghost_count += 1
        match.is_bye = True

        if match.next_loss:
            self._add_ghost(match.next_loss)

        if match.ghost_count == 2:
            if match.next_win:
                self._add_ghost(match.next_win)