use shared_kernel::normalize_required_string;

use crate::{
    JumpHopDifficulty, JumpHopError, JumpHopJumpResultKind, JumpHopLastJump, JumpHopPath,
    JumpHopPlatform, JumpHopRunSnapshot, JumpHopRunStatus, JumpHopScoring, JumpHopTileType,
};

pub fn generate_jump_hop_path(seed: &str, difficulty: JumpHopDifficulty) -> JumpHopPath {
    let config = difficulty_config(difficulty);
    let mut rng = DeterministicRng::new(seed, difficulty.as_str());
    let platform_count = rng.range_u32(config.min_platforms, config.max_platforms) as usize;
    let mut platforms = Vec::with_capacity(platform_count);
    let mut x = 0.0f32;
    let mut y = 0.0f32;

    for index in 0..platform_count {
        let tile_type = if index == 0 {
            JumpHopTileType::Start
        } else if index + 1 == platform_count {
            JumpHopTileType::Finish
        } else if index % 7 == 0 {
            JumpHopTileType::Bonus
        } else if index % 5 == 0 {
            JumpHopTileType::Target
        } else if index % 4 == 0 {
            JumpHopTileType::Accent
        } else {
            JumpHopTileType::Normal
        };
        let width = rng.range_f32(config.min_width, config.max_width);
        let height = width * rng.range_f32(0.86, 1.04);
        let landing_radius = width * config.landing_radius_factor;
        let perfect_radius = landing_radius * config.perfect_radius_factor;

        platforms.push(JumpHopPlatform {
            platform_id: format!("jump-hop-platform-{index:03}"),
            tile_type,
            x,
            y,
            width,
            height,
            landing_radius,
            perfect_radius,
            score_value: if tile_type == JumpHopTileType::Bonus {
                180
            } else {
                100
            },
        });

        if index + 1 < platform_count {
            let distance = rng.range_f32(config.min_gap, config.max_gap);
            let direction = if rng.next_u32() % 2 == 0 { 1.0 } else { -1.0 };
            x += distance * 0.62 * direction;
            y += distance;
        }
    }

    JumpHopPath {
        seed: seed.trim().to_string(),
        difficulty,
        finish_index: platform_count.saturating_sub(1) as u32,
        platforms,
        camera_preset: "portrait-isometric-9x16".to_string(),
        scoring: JumpHopScoring {
            charge_to_distance_ratio: config.charge_to_distance_ratio,
            max_charge_ms: config.max_charge_ms,
            hit_bonus: 20,
            perfect_bonus: 60,
        },
    }
}

pub fn start_run(
    run_id: String,
    owner_user_id: String,
    profile_id: String,
    path: JumpHopPath,
    started_at_ms: u64,
) -> Result<JumpHopRunSnapshot, JumpHopError> {
    let run_id = normalize_required_string(run_id).ok_or(JumpHopError::MissingRunId)?;
    let owner_user_id =
        normalize_required_string(owner_user_id).ok_or(JumpHopError::MissingOwnerUserId)?;
    let profile_id = normalize_required_string(profile_id).ok_or(JumpHopError::MissingProfileId)?;
    if path.platforms.is_empty() {
        return Err(JumpHopError::EmptyPath);
    }

    Ok(JumpHopRunSnapshot {
        run_id,
        profile_id,
        owner_user_id,
        status: JumpHopRunStatus::Playing,
        current_platform_index: 0,
        score: 0,
        combo: 0,
        last_jump: None,
        started_at_ms,
        finished_at_ms: None,
        path,
    })
}

pub fn apply_jump(
    run: &JumpHopRunSnapshot,
    charge_ms: u32,
    jumped_at_ms: u64,
) -> Result<JumpHopRunSnapshot, JumpHopError> {
    if run.status != JumpHopRunStatus::Playing {
        return Err(JumpHopError::RunNotPlaying);
    }
    let current_index = run.current_platform_index as usize;
    let next_index = current_index + 1;
    let current = run
        .path
        .platforms
        .get(current_index)
        .ok_or(JumpHopError::EmptyPath)?;
    let target = run
        .path
        .platforms
        .get(next_index)
        .ok_or(JumpHopError::NoNextPlatform)?;
    let capped_charge = charge_ms.min(run.path.scoring.max_charge_ms);
    let jump_distance = capped_charge as f32 * run.path.scoring.charge_to_distance_ratio;
    let vector_x = target.x - current.x;
    let vector_y = target.y - current.y;
    let target_distance = vector_x.hypot(vector_y).max(0.0001);
    let unit_x = vector_x / target_distance;
    let unit_y = vector_y / target_distance;
    let landed_x = current.x + unit_x * jump_distance;
    let landed_y = current.y + unit_y * jump_distance;
    let landing_error = (landed_x - target.x).hypot(landed_y - target.y);

    let mut next = run.clone();
    let result = if landing_error <= target.perfect_radius {
        if next_index as u32 == run.path.finish_index {
            JumpHopJumpResultKind::Finish
        } else {
            JumpHopJumpResultKind::Perfect
        }
    } else if landing_error <= target.landing_radius {
        if next_index as u32 == run.path.finish_index {
            JumpHopJumpResultKind::Finish
        } else {
            JumpHopJumpResultKind::Hit
        }
    } else {
        JumpHopJumpResultKind::Miss
    };

    next.last_jump = Some(JumpHopLastJump {
        charge_ms: capped_charge,
        jump_distance,
        target_platform_index: next_index as u32,
        landed_x,
        landed_y,
        result,
    });

    if result == JumpHopJumpResultKind::Miss {
        next.status = JumpHopRunStatus::Failed;
        next.combo = 0;
        next.finished_at_ms = Some(jumped_at_ms);
        return Ok(next);
    }

    next.current_platform_index = next_index as u32;
    next.combo = next.combo.saturating_add(1);
    next.score = next.score.saturating_add(target.score_value);
    if matches!(
        result,
        JumpHopJumpResultKind::Perfect | JumpHopJumpResultKind::Finish
    ) {
        next.score = next
            .score
            .saturating_add(run.path.scoring.perfect_bonus)
            .saturating_add(next.combo.saturating_mul(run.path.scoring.hit_bonus));
    } else {
        next.score = next.score.saturating_add(run.path.scoring.hit_bonus);
    }
    if result == JumpHopJumpResultKind::Finish {
        next.status = JumpHopRunStatus::Cleared;
        next.finished_at_ms = Some(jumped_at_ms);
    }

    Ok(next)
}

pub fn restart_run(
    run: &JumpHopRunSnapshot,
    next_run_id: String,
    restarted_at_ms: u64,
) -> Result<JumpHopRunSnapshot, JumpHopError> {
    start_run(
        next_run_id,
        run.owner_user_id.clone(),
        run.profile_id.clone(),
        run.path.clone(),
        restarted_at_ms,
    )
}

struct DifficultyConfig {
    min_platforms: u32,
    max_platforms: u32,
    min_gap: f32,
    max_gap: f32,
    min_width: f32,
    max_width: f32,
    landing_radius_factor: f32,
    perfect_radius_factor: f32,
    charge_to_distance_ratio: f32,
    max_charge_ms: u32,
}

fn difficulty_config(difficulty: JumpHopDifficulty) -> DifficultyConfig {
    match difficulty {
        JumpHopDifficulty::Easy => DifficultyConfig {
            min_platforms: 12,
            max_platforms: 14,
            min_gap: 1.0,
            max_gap: 1.45,
            min_width: 0.9,
            max_width: 1.08,
            landing_radius_factor: 0.62,
            perfect_radius_factor: 0.32,
            charge_to_distance_ratio: 0.004,
            max_charge_ms: 700,
        },
        JumpHopDifficulty::Standard => DifficultyConfig {
            min_platforms: 16,
            max_platforms: 18,
            min_gap: 1.22,
            max_gap: 1.78,
            min_width: 0.82,
            max_width: 1.0,
            landing_radius_factor: 0.54,
            perfect_radius_factor: 0.26,
            charge_to_distance_ratio: 0.004,
            max_charge_ms: 780,
        },
        JumpHopDifficulty::Advanced => DifficultyConfig {
            min_platforms: 20,
            max_platforms: 24,
            min_gap: 1.45,
            max_gap: 2.05,
            min_width: 0.72,
            max_width: 0.94,
            landing_radius_factor: 0.48,
            perfect_radius_factor: 0.22,
            charge_to_distance_ratio: 0.004,
            max_charge_ms: 860,
        },
        JumpHopDifficulty::Challenge => DifficultyConfig {
            min_platforms: 26,
            max_platforms: 32,
            min_gap: 1.7,
            max_gap: 2.35,
            min_width: 0.66,
            max_width: 0.88,
            landing_radius_factor: 0.42,
            perfect_radius_factor: 0.18,
            charge_to_distance_ratio: 0.004,
            max_charge_ms: 950,
        },
    }
}

struct DeterministicRng {
    state: u64,
}

impl DeterministicRng {
    fn new(seed: &str, salt: &str) -> Self {
        let mut state = 0xcbf2_9ce4_8422_2325u64;
        for byte in seed.bytes().chain(salt.bytes()) {
            state ^= u64::from(byte);
            state = state.wrapping_mul(0x1000_0000_01b3);
        }
        Self { state }
    }

    fn next_u32(&mut self) -> u32 {
        self.state = self
            .state
            .wrapping_mul(6_364_136_223_846_793_005)
            .wrapping_add(1);
        (self.state >> 32) as u32
    }

    fn range_u32(&mut self, min: u32, max: u32) -> u32 {
        if max <= min {
            return min;
        }
        min + self.next_u32() % (max - min + 1)
    }

    fn range_f32(&mut self, min: f32, max: f32) -> f32 {
        if max <= min {
            return min;
        }
        let unit = self.next_u32() as f32 / u32::MAX as f32;
        min + (max - min) * unit
    }
}

#[cfg(test)]
mod tests {
    use crate::{
        JumpHopDifficulty, JumpHopJumpResultKind, JumpHopRunStatus, apply_jump,
        generate_jump_hop_path, restart_run, start_run,
    };

    #[test]
    fn path_generation_is_seeded_and_uses_difficulty_ranges() {
        let first = generate_jump_hop_path("seed-a", JumpHopDifficulty::Standard);
        let second = generate_jump_hop_path("seed-a", JumpHopDifficulty::Standard);
        let challenge = generate_jump_hop_path("seed-a", JumpHopDifficulty::Challenge);

        assert_eq!(first, second);
        assert!((16..=18).contains(&first.platforms.len()));
        assert!((26..=32).contains(&challenge.platforms.len()));
        assert_eq!(first.platforms.first().unwrap().tile_type.as_str(), "start");
        assert_eq!(first.platforms.last().unwrap().tile_type.as_str(), "finish");
    }

    #[test]
    fn jump_resolution_distinguishes_perfect_hit_and_miss() {
        let path = generate_jump_hop_path("seed-b", JumpHopDifficulty::Easy);
        let run = start_run(
            "run-1".to_string(),
            "user-1".to_string(),
            "profile-1".to_string(),
            path,
            100,
        )
        .expect("run should start");
        let target = &run.path.platforms[1];
        let distance = target.x.hypot(target.y);
        let perfect_charge = (distance / run.path.scoring.charge_to_distance_ratio) as u32;

        let perfect = apply_jump(&run, perfect_charge, 200).expect("jump should resolve");
        assert_eq!(
            perfect.last_jump.as_ref().unwrap().result,
            JumpHopJumpResultKind::Perfect
        );
        assert_eq!(perfect.status, JumpHopRunStatus::Playing);
        assert_eq!(perfect.current_platform_index, 1);

        let hit = apply_jump(&run, perfect_charge.saturating_add(80), 200)
            .expect("jump should resolve");
        assert_eq!(
            hit.last_jump.as_ref().unwrap().result,
            JumpHopJumpResultKind::Hit
        );

        let miss = apply_jump(&run, perfect_charge.saturating_add(900), 200)
            .expect("jump should resolve");
        assert_eq!(miss.status, JumpHopRunStatus::Failed);
        assert_eq!(
            miss.last_jump.as_ref().unwrap().result,
            JumpHopJumpResultKind::Miss
        );
    }

    #[test]
    fn restart_returns_to_first_platform_and_playing_state() {
        let path = generate_jump_hop_path("seed-c", JumpHopDifficulty::Easy);
        let mut run = start_run(
            "run-1".to_string(),
            "user-1".to_string(),
            "profile-1".to_string(),
            path,
            100,
        )
        .expect("run should start");
        run.status = JumpHopRunStatus::Failed;
        run.current_platform_index = 3;
        run.score = 300;
        run.combo = 2;
        run.finished_at_ms = Some(200);

        let restarted = restart_run(&run, "run-2".to_string(), 300).expect("run should restart");

        assert_eq!(restarted.run_id, "run-2");
        assert_eq!(restarted.status, JumpHopRunStatus::Playing);
        assert_eq!(restarted.current_platform_index, 0);
        assert_eq!(restarted.score, 0);
        assert_eq!(restarted.combo, 0);
        assert!(restarted.last_jump.is_none());
        assert_eq!(restarted.started_at_ms, 300);
        assert!(restarted.finished_at_ms.is_none());
    }
}