//! Cash game and tournament series simulation runners.
//!
//! Provides:
//! - [`run_cash_game`] — runs a cash game simulation
//! - [`run_sng_series`] — runs multiple SNG tournaments and aggregates results

use std::collections::{HashMap, HashSet};

use rand::seq::SliceRandom;
use rand::{Rng, SeedableRng};

use super::bot_factory;
use super::config::GameConfig;
use super::stats::{SimulationStats, SngSeriesResult};
use super::table::Table;
use super::tournament::Tournament;
use super::types::{ChipCount, GameError, PlayerId};

/// Runs a cash game simulation based on the given configuration.
///
/// # Workflow
///
/// 1. Creates a [`Table`] from `config.to_table_config()`
/// 2. Creates bots from `config.bots` via [`bot_factory::create_bot`]
/// 3. Seats bots at the table (using `BotConfig.seat` if specified, otherwise auto-assigns)
/// 4. Runs `config.num_hands` hands
/// 5. Collects statistics via [`SimulationStats`]
/// 6. Returns `(SimulationStats, Table)` with final state
///
/// # Errors
///
/// Returns [`GameError`] if:
/// - A bot type is unknown
/// - The table is full
/// - There are not enough players
/// - A hand fails to execute
pub fn run_cash_game(config: &GameConfig) -> Result<(SimulationStats, Table), GameError> {
    // Validate that we have at least 2 bots.
    if config.bots.len() < 2 {
        return Err(GameError::NotEnoughPlayers(config.bots.len()));
    }

    // 1. Create the table.
    let table_config = config.to_table_config();
    let mut table = Table::new(table_config);

    // Apply seed if configured.
    if let Some(seed) = config.seed {
        table = table.with_seed(seed);
    }

    // 2. Create bots and track player names.
    let mut player_names: HashMap<PlayerId, String> = HashMap::new();
    let mut starting_stacks: HashMap<PlayerId, ChipCount> = HashMap::new();

    for (i, bot_config) in config.bots.iter().enumerate() {
        let player_id = PlayerId(i as u64);
        let bot = bot_factory::create_bot(bot_config, player_id).map_err(GameError::Custom)?;

        // Store the name before seating (seating consumes the bot).
        let name = bot.name().to_string();
        player_names.insert(player_id, name);
        starting_stacks.insert(player_id, config.starting_chips);

        // 3. Seat the bot.
        let seat_index = bot_config
            .seat
            .unwrap_or_else(|| table.find_empty_seat().unwrap_or(i as u8));

        table.seat_player(seat_index, bot, config.starting_chips)?;
    }

    // 4. Run hands and collect stats.
    let mut stats = SimulationStats::new("Cash");

    for _ in 0..config.num_hands {
        match table.run_hand() {
            Ok(result) => {
                stats.record_hand_result(&result, &player_names);

                // Auto-rebuy: top up players whose stack dropped below the
                // configured percentage of starting chips.
                // Also reactivates busted players (stack=0, SittingOut) so
                // they can continue playing all hands.
                if config.auto_rebuy {
                    // NOTE: Integer division truncates — e.g. 99 * 25 / 100 = 24 (not 24.75).
                    // This is acceptable for simulation purposes; the threshold is slightly
                    // lower than the exact percentage, which is conservative (rebuys trigger
                    // slightly earlier). Uses saturating_mul to prevent overflow with extreme
                    // chip values.
                    let threshold = config.starting_chips
                        .saturating_mul(config.rebuy_threshold_percentage as ChipCount)
                        / 100;
                    for slot in table.seats_mut().iter_mut() {
                        if let Some(seat) = slot {
                            if seat.stack < threshold {
                                let rebuy_amount =
                                    config.starting_chips.saturating_sub(seat.stack);
                                log::info!(
                                    "Auto-rebuy: {} topped up by {} (was {})",
                                    seat.player.name(),
                                    rebuy_amount,
                                    seat.stack
                                );
                                seat.stack = config.starting_chips;
                                // Reactivate busted players so they can play
                                // the next hand.
                                if seat.state == super::player_info::PlayerState::SittingOut {
                                    seat.state = super::player_info::PlayerState::Active;
                                }
                            }
                        }
                    }
                }
            }
            Err(GameError::NotEnoughPlayers(_)) => {
                // Not enough active players to continue.
                break;
            }
            Err(e) => {
                return Err(e);
            }
        }
    }

    // 5. Record final stacks and bankrolls for accurate profit calculation.
    let final_stacks: HashMap<PlayerId, ChipCount> = table
        .seats()
        .iter()
        .filter_map(|slot| {
            slot.as_ref()
                .map(|seat| (seat.player_id, seat.stack))
        })
        .collect();
    let bankrolls: HashMap<PlayerId, i64> = table
        .seats()
        .iter()
        .filter_map(|slot| {
            slot.as_ref()
                .map(|seat| (seat.player_id, seat.bankroll))
        })
        .collect();
    let bankroll_mode = config.reset_bankroll_each_hand || config.bankroll_refill_threshold > 0;
    stats.record_final_stacks(&final_stacks, &starting_stacks, &bankrolls, bankroll_mode);

    Ok((stats, table))
}

/// Runs a series of tournaments (SNG or MTT) and returns aggregate results.
///
/// For each tournament:
/// 1. Creates a new [`Tournament`] with the given config's schedule, prizes,
///    starting chips, and buy-in.
/// 2. Creates fresh bot instances via [`bot_factory::create_bot`] for each
///    bot config.
/// 3. Shuffles the registration order (if `config.randomize_seats`) to
///    randomize seat assignments.
/// 4. Registers all bots with the tournament.
/// 5. Runs the tournament to completion.
/// 6. Records each player's placement and prize money.
///
/// Players are tracked **by name** across tournaments (since each tournament
/// creates fresh bot instances with different [`PlayerId`]s).
///
/// Works for both `SitAndGo` and `MultiTableTournament` game types.
/// For MTT, uses `config.num_tables` to create the appropriate number of tables.
///
/// # Errors
///
/// Returns [`GameError`] if:
/// - Fewer than 2 bots are configured
/// - Bot names are not unique (would cause result aggregation to merge players)
/// - A bot type is unknown
/// - The table is full
/// - A tournament fails to complete
pub fn run_sng_series(
    config: &GameConfig,
    num_tournaments: u32,
) -> Result<SngSeriesResult, GameError> {
    // Validate that we have at least 2 bots.
    if config.bots.len() < 2 {
        return Err(GameError::NotEnoughPlayers(config.bots.len()));
    }

    // Validate unique bot names — players are tracked by name across tournaments,
    // so duplicate names would silently merge their results.
    // Bots without explicit names use their bot_type as a fallback identity.
    let unique_names: HashSet<String> = config
        .bots
        .iter()
        .map(|b| b.name.clone().unwrap_or_else(|| b.bot_type.clone()))
        .collect();
    if unique_names.len() != config.bots.len() {
        return Err(GameError::Custom(
            "Duplicate bot names in config: each bot must have a unique name for series tracking".to_string(),
        ));
    }

    let buy_in = if config.buy_in > 0 {
        config.buy_in
    } else {
        config.starting_chips
    };

    // Build a deterministic RNG for shuffling registration order.
    // Use the config seed if provided, otherwise generate a random one
    // and log it so the run can be reproduced.
    let base_seed = config.seed.unwrap_or_else(|| {
        let seed = rand::rng().random::<u64>();
        log::info!("Generated random seed for tournament series: {}", seed);
        seed
    });

    let mut result = SngSeriesResult::new(num_tournaments, buy_in, base_seed);

    for tournament_index in 0..num_tournaments {
        let table_config = config.to_table_config();
        let blind_schedule = config.to_blind_schedule();
        let prize_structure = config.to_prize_structure();

        // Create the appropriate tournament type based on game_type.
        let mut tournament = match config.game_type {
            super::tournament::GameType::MultiTableTournament => Tournament::new_mtt(
                config.num_tables,
                table_config,
                blind_schedule,
                prize_structure,
                config.starting_chips,
                buy_in,
            ),
            _ => Tournament::new_sng(
                table_config,
                blind_schedule,
                prize_structure,
                config.starting_chips,
                buy_in,
            ),
        };

        // Build the registration order. If randomize_seats is enabled,
        // shuffle the bot order using a seed derived from the base seed +
        // tournament index for reproducibility.
        let mut order: Vec<usize> = (0..config.bots.len()).collect();
        if config.randomize_seats {
            let tournament_seed = base_seed.wrapping_add(tournament_index as u64);
            let mut rng = rand::rngs::StdRng::seed_from_u64(tournament_seed);
            order.shuffle(&mut rng);
        }

        // Create fresh bots and register them in the (possibly shuffled) order.
        // We need to track names by PlayerId for this tournament.
        let mut player_names: HashMap<PlayerId, String> = HashMap::new();

        for (seat_seq, &bot_idx) in order.iter().enumerate() {
            let bot_config = &config.bots[bot_idx];
            let player_id = PlayerId(seat_seq as u64);
            let bot = bot_factory::create_bot(bot_config, player_id)
                .map_err(GameError::Custom)?;

            let name = bot.name().to_string();
            player_names.insert(player_id, name);

            tournament.register_player(bot)?;
        }

        // Run the tournament to completion.
        log::info!("Running tournament {}/{}...", tournament_index + 1, num_tournaments);
        tournament.run_to_completion()?;

        // Accumulate total hands.
        result.total_hands_played += tournament.total_hands();

        // Process results: record eliminated players from standings.
        let standings = tournament.standings();

        // Invariant: after run_to_completion(), standings should have N-1 entries
        // and winner() returns the sole remaining player. Log a warning if violated.
        let expected_standings = player_names.len().saturating_sub(1);
        if standings.len() != expected_standings {
            log::warn!(
                "Tournament {} ended with {} standings (expected {})",
                tournament_index + 1,
                standings.len(),
                expected_standings
            );
        }

        // Track which player IDs have been recorded to prevent double-counting.
        let mut recorded: HashSet<PlayerId> = HashSet::new();

        // Standings contain eliminated players with raw placement numbers.
        // In the tournament, placement = N means the player was the Nth-to-last
        // to be eliminated (i.e., placement=N is the worst finish).
        // For a 10-player tournament: first player out gets placement=10,
        // last player eliminated gets placement=2. The winner (placement=1)
        // is NOT in standings — they are tracked separately via winner().
        //
        // The raw placement IS the finish position, so we use it directly
        // for prize lookup (prize_for_placement is 1-indexed).
        for &(player_id, raw_placement) in standings.iter() {
            let finish_position = raw_placement;
            let name = player_names
                .get(&player_id)
                .cloned()
                .unwrap_or_else(|| format!("Player({})", player_id.0));

            let prize = tournament
                .prize_structure()
                .prize_for_placement(finish_position)
                .unwrap_or(0);

            log::debug!(
                "Tournament {}: {} raw_placement={} finish={} prize={}",
                tournament_index + 1, name, raw_placement, finish_position, prize
            );

            result.record_player_finish(&name, finish_position, prize);
            recorded.insert(player_id);
        }

        // Record the winner (last active player) if not already in standings.
        // The winner is the sole remaining player who was never eliminated.
        if let Some(winner_id) = tournament.winner() {
            if !recorded.contains(&winner_id) {
                let name = player_names
                    .get(&winner_id)
                    .cloned()
                    .unwrap_or_else(|| format!("Player({})", winner_id.0));

                let prize = tournament
                    .prize_structure()
                    .prize_for_placement(1)
                    .unwrap_or(0);

                result.record_player_finish(&name, 1, prize);
            }
        }
    }

    Ok(result)
}

// ===========================================================================
// Tests
// ===========================================================================

#[cfg(test)]
mod tests {
    use super::*;
    use crate::game::config::{BetLimitConfig, BotConfig};
    use crate::game::tournament::GameType;
    use std::collections::HashMap;

    fn make_cash_config(num_hands: u64, seed: Option<u64>) -> GameConfig {
        GameConfig {
            game_type: GameType::Cash,
            num_seats: 6,
            bet_limit: BetLimitConfig::NoLimit { min_raise: 20 },
            small_blind: 10,
            big_blind: 20,
            ante: 0,
            starting_chips: 10_000,
            buy_in: 0,
            num_tables: 1,
            hands_per_level: 10,
            num_blind_levels: 15,
            num_hands,
            seed,
            rake_percentage: 0.0,
            rake_cap: 0,
            reset_bankroll_each_hand: false,
            bankroll_refill_threshold: 0,
            randomize_seats: false,
            auto_rebuy: false,
            rebuy_threshold_percentage: 25,
            blind_levels: vec![],
            prizes: vec![],
            num_tournaments: 1,
            bots: vec![
                BotConfig {
                    bot_type: "call_bot".to_string(),
                    name: Some("Alice".to_string()),
                    seat: Some(0),
                    parameters: HashMap::new(),
                },
                BotConfig {
                    bot_type: "call_bot".to_string(),
                    name: Some("Bob".to_string()),
                    seat: Some(1),
                    parameters: HashMap::new(),
                },
                BotConfig {
                    bot_type: "fold_bot".to_string(),
                    name: Some("Charlie".to_string()),
                    seat: Some(2),
                    parameters: HashMap::new(),
                },
            ],
        }
    }

    #[test]
    fn run_cash_game_basic() {
        let config = make_cash_config(10, Some(42));
        let result = run_cash_game(&config);
        assert!(result.is_ok());

        let (stats, _table) = result.unwrap();
        assert_eq!(stats.total_hands, 10);
        assert_eq!(stats.players.len(), 3);
        assert_eq!(stats.game_type, "Cash");

        // All players should have played 10 hands.
        for stats in stats.players.values() {
            assert_eq!(stats.hands_played, 10);
        }

        // Total profit across all players should sum to zero (zero-sum game).
        let total_profit: i64 = stats.players.values().map(|p| p.total_profit).sum();
        assert_eq!(total_profit, 0);
    }

    #[test]
    fn run_cash_game_reproducible_with_seed() {
        let config1 = make_cash_config(50, Some(12345));
        let config2 = make_cash_config(50, Some(12345));

        let (stats1, _) = run_cash_game(&config1).unwrap();
        let (stats2, _) = run_cash_game(&config2).unwrap();

        // Same seed should produce identical results.
        for pid in stats1.players.keys() {
            let p1 = stats1.players.get(pid).unwrap();
            let p2 = stats2.players.get(pid).unwrap();
            assert_eq!(p1.total_profit, p2.total_profit);
            assert_eq!(p1.hands_won, p2.hands_won);
            assert_eq!(p1.final_stack, p2.final_stack);
        }
    }

    #[test]
    fn run_cash_game_different_seeds_differ() {
        let config1 = make_cash_config(50, Some(111));
        let config2 = make_cash_config(50, Some(222));

        let (stats1, _) = run_cash_game(&config1).unwrap();
        let (stats2, _) = run_cash_game(&config2).unwrap();

        // Different seeds should (almost certainly) produce different results.
        let profits1: Vec<i64> = stats1
            .players
            .values()
            .map(|p| p.total_profit)
            .collect();
        let profits2: Vec<i64> = stats2
            .players
            .values()
            .map(|p| p.total_profit)
            .collect();

        assert_ne!(profits1, profits2);
    }

    #[test]
    fn run_cash_game_not_enough_bots() {
        let config = GameConfig {
            game_type: GameType::Cash,
            num_seats: 6,
            bet_limit: BetLimitConfig::NoLimit { min_raise: 20 },
            small_blind: 10,
            big_blind: 20,
            ante: 0,
            starting_chips: 10_000,
            buy_in: 0,
            num_tables: 1,
            hands_per_level: 10,
            num_blind_levels: 15,
            num_hands: 10,
            seed: None,
            rake_percentage: 0.0,
            rake_cap: 0,
            reset_bankroll_each_hand: false,
            bankroll_refill_threshold: 0,
            randomize_seats: false,
            auto_rebuy: false,
            rebuy_threshold_percentage: 25,
            blind_levels: vec![],
            prizes: vec![],
            num_tournaments: 1,

            bots: vec![BotConfig {
                bot_type: "call_bot".to_string(),
                name: Some("Lonely".to_string()),
                seat: None,
                parameters: HashMap::new(),
            }],
        };

        let result = run_cash_game(&config);
        assert!(result.is_err());
    }

    #[test]
    fn run_cash_game_unknown_bot_type() {
        let config = GameConfig {
            game_type: GameType::Cash,
            num_seats: 6,
            bet_limit: BetLimitConfig::NoLimit { min_raise: 20 },
            small_blind: 10,
            big_blind: 20,
            ante: 0,
            starting_chips: 10_000,
            buy_in: 0,
            num_tables: 1,
            hands_per_level: 10,
            num_blind_levels: 15,
            num_hands: 10,
            seed: None,
            rake_percentage: 0.0,
            rake_cap: 0,
            reset_bankroll_each_hand: false,
            bankroll_refill_threshold: 0,
            randomize_seats: false,
            auto_rebuy: false,
            rebuy_threshold_percentage: 25,
            blind_levels: vec![],
            prizes: vec![],
            num_tournaments: 1,
            bots: vec![
                BotConfig {
                    bot_type: "call_bot".to_string(),
                    name: Some("Alice".to_string()),
                    seat: Some(0),
                    parameters: HashMap::new(),
                },
                BotConfig {
                    bot_type: "super_ai".to_string(),
                    name: Some("Bob".to_string()),
                    seat: Some(1),
                    parameters: HashMap::new(),
                },
            ],
        };

        let result = run_cash_game(&config);
        assert!(result.is_err());
    }

    #[test]
    fn run_cash_game_auto_seat_assignment() {
        let config = GameConfig {
            game_type: GameType::Cash,
            num_seats: 6,
            bet_limit: BetLimitConfig::NoLimit { min_raise: 20 },
            small_blind: 10,
            big_blind: 20,
            ante: 0,
            starting_chips: 10_000,
            buy_in: 0,
            num_tables: 1,
            hands_per_level: 10,
            num_blind_levels: 15,
            num_hands: 5,
            seed: Some(99),
            rake_percentage: 0.0,
            rake_cap: 0,
            reset_bankroll_each_hand: false,
            bankroll_refill_threshold: 0,
            randomize_seats: false,
            auto_rebuy: false,
            rebuy_threshold_percentage: 25,
            blind_levels: vec![],
            prizes: vec![],
            num_tournaments: 1,

            bots: vec![
                BotConfig {
                    bot_type: "call_bot".to_string(),
                    name: Some("A".to_string()),
                    seat: None, // auto-assign
                    parameters: HashMap::new(),
                },
                BotConfig {
                    bot_type: "fold_bot".to_string(),
                    name: Some("B".to_string()),
                    seat: None, // auto-assign
                    parameters: HashMap::new(),
                },
            ],
        };

        let result = run_cash_game(&config);
        assert!(result.is_ok());
        let (stats, table) = result.unwrap();
        assert_eq!(stats.total_hands, 5);
        // Both players should be seated.
        assert_eq!(table.seated_player_count(), 2);
    }

    #[test]
    fn run_cash_game_summary() {
        let config = make_cash_config(20, Some(42));
        let (stats, _) = run_cash_game(&config).unwrap();

        let summary = stats.summary(10_000);
        assert!(summary.contains("=== Simulation Results ==="));
        assert!(summary.contains("Cash"));
        assert!(summary.contains("20"));
        assert!(summary.contains("Alice"));
        assert!(summary.contains("Bob"));
        assert!(summary.contains("Charlie"));
    }

    #[test]
    fn test_cash_game_auto_rebuy() {
        let config = GameConfig {
            game_type: GameType::Cash,
            num_seats: 6,
            bet_limit: BetLimitConfig::NoLimit { min_raise: 10 },
            small_blind: 5,
            big_blind: 10,
            ante: 0,
            starting_chips: 100,
            buy_in: 0,
            num_tables: 1,
            hands_per_level: 10,
            num_blind_levels: 15,
            num_hands: 5,
            seed: Some(42),
            rake_percentage: 0.0,
            rake_cap: 0,
            reset_bankroll_each_hand: false,
            bankroll_refill_threshold: 0,
            randomize_seats: false,
            auto_rebuy: true,
            rebuy_threshold_percentage: 25,
            blind_levels: vec![],
            prizes: vec![],
            num_tournaments: 1,
            bots: vec![
                BotConfig {
                    bot_type: "call_bot".to_string(),
                    name: Some("Alice".to_string()),
                    seat: Some(0),
                    parameters: HashMap::new(),
                },
                BotConfig {
                    bot_type: "call_bot".to_string(),
                    name: Some("Bob".to_string()),
                    seat: Some(1),
                    parameters: HashMap::new(),
                },
            ],
        };

        let result = run_cash_game(&config);
        assert!(result.is_ok(), "run_cash_game should succeed");

        let (_stats, table) = result.unwrap();
        // With auto_rebuy enabled, players who drop below 25% of starting chips
        // (threshold = 100/4 = 25) should be topped back up to starting_chips.
        // Players above the threshold should remain unchanged.
        // Busted players (stack=0, SittingOut) should be reactivated.
        for slot in table.seats().iter() {
            if let Some(seat) = slot {
                // After rebuy, stack should either be at starting_chips (was rebought)
                // or above the threshold of 25 (was not eligible for rebuy).
                assert!(
                    seat.stack >= 25 || seat.stack == 100,
                    "Player {} should have chips >= 25 or be rebought to 100 after auto-rebuy, but has {}",
                    seat.player.name(),
                    seat.stack
                );
            }
        }
    }
}