#include "collision.hh"
#include "scenemanager.hh"

#include <psyqo/fixed-point.hh>

// Helper type alias for brevity
using FP = psyqo::FixedPoint<12>;

namespace psxsplash {

// Static member initialization
psyqo::FixedPoint<12> SpatialGrid::WORLD_MIN = FP(-16);
psyqo::FixedPoint<12> SpatialGrid::WORLD_MAX = FP(16);
psyqo::FixedPoint<12> SpatialGrid::CELL_SIZE = FP(4); // (32 / 8) = 4

// AABB expand implementation
void AABB::expand(const psyqo::Vec3& delta) {
    psyqo::FixedPoint<12> zero;
    if (delta.x > zero) max.x = max.x + delta.x;
    else min.x = min.x + delta.x;
    if (delta.y > zero) max.y = max.y + delta.y;
    else min.y = min.y + delta.y;
    if (delta.z > zero) max.z = max.z + delta.z;
    else min.z = min.z + delta.z;
}

// ============================================================================
// SpatialGrid Implementation
// ============================================================================

void SpatialGrid::clear() {
    for (int i = 0; i < CELL_COUNT; i++) {
        m_cells[i].count = 0;
    }
}

void SpatialGrid::worldToGrid(const psyqo::Vec3& pos, int& gx, int& gy, int& gz) const {
    // Clamp position to world bounds
    auto px = pos.x;
    auto py = pos.y;
    auto pz = pos.z;
    
    if (px < WORLD_MIN) px = WORLD_MIN;
    if (px > WORLD_MAX) px = WORLD_MAX;
    if (py < WORLD_MIN) py = WORLD_MIN;
    if (py > WORLD_MAX) py = WORLD_MAX;
    if (pz < WORLD_MIN) pz = WORLD_MIN;
    if (pz > WORLD_MAX) pz = WORLD_MAX;
    
    // Convert to grid coordinates (0 to GRID_SIZE-1)
    // Using integer division after scaling
    gx = ((px - WORLD_MIN) / CELL_SIZE).integer();
    gy = ((py - WORLD_MIN) / CELL_SIZE).integer();
    gz = ((pz - WORLD_MIN) / CELL_SIZE).integer();
    
    // Clamp to valid range
    if (gx < 0) gx = 0;
    if (gx >= GRID_SIZE) gx = GRID_SIZE - 1;
    if (gy < 0) gy = 0;
    if (gy >= GRID_SIZE) gy = GRID_SIZE - 1;
    if (gz < 0) gz = 0;
    if (gz >= GRID_SIZE) gz = GRID_SIZE - 1;
}

int SpatialGrid::getCellIndex(const psyqo::Vec3& pos) const {
    int gx, gy, gz;
    worldToGrid(pos, gx, gy, gz);
    return gx + gy * GRID_SIZE + gz * GRID_SIZE * GRID_SIZE;
}

void SpatialGrid::insert(uint16_t objectIndex, const AABB& bounds) {
    // Get grid range for this AABB
    int minGx, minGy, minGz;
    int maxGx, maxGy, maxGz;
    
    worldToGrid(bounds.min, minGx, minGy, minGz);
    worldToGrid(bounds.max, maxGx, maxGy, maxGz);
    
    // Insert into all overlapping cells
    for (int gz = minGz; gz <= maxGz; gz++) {
        for (int gy = minGy; gy <= maxGy; gy++) {
            for (int gx = minGx; gx <= maxGx; gx++) {
                int cellIndex = gx + gy * GRID_SIZE + gz * GRID_SIZE * GRID_SIZE;
                Cell& cell = m_cells[cellIndex];
                
                if (cell.count < MAX_OBJECTS_PER_CELL) {
                    cell.objectIndices[cell.count++] = objectIndex;
                }
                // If cell is full, object won't be in this cell (may miss collisions)
                // This is a tradeoff for memory/performance
            }
        }
    }
}

int SpatialGrid::queryAABB(const AABB& bounds, uint16_t* output, int maxResults) const {
    int resultCount = 0;
    
    // Get grid range for query AABB
    int minGx, minGy, minGz;
    int maxGx, maxGy, maxGz;
    
    worldToGrid(bounds.min, minGx, minGy, minGz);
    worldToGrid(bounds.max, maxGx, maxGy, maxGz);
    
    // Track which objects we've already added (two 32-bit masks for objects 0-63)
    uint32_t addedMaskLow = 0;  // Objects 0-31
    uint32_t addedMaskHigh = 0; // Objects 32-63
    
    // Query all overlapping cells
    for (int gz = minGz; gz <= maxGz; gz++) {
        for (int gy = minGy; gy <= maxGy; gy++) {
            for (int gx = minGx; gx <= maxGx; gx++) {
                int cellIndex = gx + gy * GRID_SIZE + gz * GRID_SIZE * GRID_SIZE;
                const Cell& cell = m_cells[cellIndex];
                
                for (int i = 0; i < cell.count; i++) {
                    uint16_t objIndex = cell.objectIndices[i];
                    
                    // Skip if already added (using bitmask for objects 0-63)
                    if (objIndex < 32) {
                        uint32_t bit = 1U << objIndex;
                        if (addedMaskLow & bit) continue;
                        addedMaskLow |= bit;
                    } else if (objIndex < 64) {
                        uint32_t bit = 1U << (objIndex - 32);
                        if (addedMaskHigh & bit) continue;
                        addedMaskHigh |= bit;
                    }
                    
                    if (resultCount < maxResults) {
                        output[resultCount++] = objIndex;
                    }
                }
            }
        }
    }
    
    return resultCount;
}

// ============================================================================
// CollisionSystem Implementation
// ============================================================================

void CollisionSystem::init() {
    reset();
}

void CollisionSystem::reset() {
    m_colliderCount = 0;
    m_resultCount = 0;
    m_triggerPairCount = 0;
    m_grid.clear();
}

void CollisionSystem::registerCollider(uint16_t gameObjectIndex, const AABB& localBounds,
                                        CollisionType type, CollisionMask mask) {
    if (m_colliderCount >= MAX_COLLIDERS) {
        // Out of collider slots
        return;
    }
    
    CollisionData& data = m_colliders[m_colliderCount++];
    data.bounds = localBounds;  // Will be transformed in updateCollider
    data.type = type;
    data.layerMask = mask;
    data.flags = 0;
    data.gridCell = 0;
    data.gameObjectIndex = gameObjectIndex;
}

void CollisionSystem::updateCollider(uint16_t gameObjectIndex, const psyqo::Vec3& position,
                                      const psyqo::Matrix33& rotation) {
    // Find the collider for this object
    for (int i = 0; i < m_colliderCount; i++) {
        if (m_colliders[i].gameObjectIndex == gameObjectIndex) {
            // For now, just translate the AABB (no rotation support for AABBs)
            // TODO: Compute rotated AABB if needed
            
            // Store original local bounds somewhere if we need to recalculate
            // For now, assume bounds are already world-relative
            m_colliders[i].bounds.min = m_colliders[i].bounds.min + position;
            m_colliders[i].bounds.max = m_colliders[i].bounds.max + position;
            break;
        }
    }
}

int CollisionSystem::detectCollisions() {
    m_resultCount = 0;
    
    // Clear and rebuild spatial grid
    m_grid.clear();
    for (int i = 0; i < m_colliderCount; i++) {
        m_grid.insert(i, m_colliders[i].bounds);
    }
    
    // Check each collider against potential colliders from grid
    for (int i = 0; i < m_colliderCount; i++) {
        const CollisionData& colliderA = m_colliders[i];
        
        // Skip if no collision type
        if (colliderA.type == CollisionType::None) continue;
        
        // Query spatial grid for nearby objects
        uint16_t nearby[32];
        int nearbyCount = m_grid.queryAABB(colliderA.bounds, nearby, 32);
        
        for (int j = 0; j < nearbyCount; j++) {
            int otherIndex = nearby[j];
            
            // Skip self
            if (otherIndex == i) continue;
            
            // Skip if already processed (only process pairs once)
            if (otherIndex < i) continue;
            
            const CollisionData& colliderB = m_colliders[otherIndex];
            
            // Skip if no collision type
            if (colliderB.type == CollisionType::None) continue;
            
            // Check layer masks
            if ((colliderA.layerMask & colliderB.layerMask) == 0) continue;
            
            // Narrowphase AABB test
            psyqo::Vec3 normal;
            psyqo::FixedPoint<12> penetration;
            
            if (testAABB(colliderA.bounds, colliderB.bounds, normal, penetration)) {
                // Collision detected
                if (m_resultCount < MAX_COLLISION_RESULTS) {
                    CollisionResult& result = m_results[m_resultCount++];
                    result.objectA = colliderA.gameObjectIndex;
                    result.objectB = colliderB.gameObjectIndex;
                    result.normal = normal;
                    result.penetration = penetration;
                }
                
                // Handle triggers
                if (colliderA.type == CollisionType::Trigger) {
                    updateTriggerState(i, otherIndex, true);
                }
                if (colliderB.type == CollisionType::Trigger) {
                    updateTriggerState(otherIndex, i, true);
                }
            }
        }
    }
    
    // Update trigger pairs that are no longer overlapping
    for (int i = 0; i < m_triggerPairCount; i++) {
        TriggerPair& pair = m_triggerPairs[i];
        pair.framesSinceContact++;
        
        // If no contact for several frames, trigger exit
        if (pair.framesSinceContact > 2 && pair.state != 2) {
            pair.state = 2; // Exiting
        }
    }
    
    return m_resultCount;
}

bool CollisionSystem::testAABB(const AABB& a, const AABB& b,
                                psyqo::Vec3& normal, psyqo::FixedPoint<12>& penetration) const {
    // Check for overlap on all axes
    if (a.max.x < b.min.x || a.min.x > b.max.x) return false;
    if (a.max.y < b.min.y || a.min.y > b.max.y) return false;
    if (a.max.z < b.min.z || a.min.z > b.max.z) return false;
    
    // Calculate penetration on each axis
    auto overlapX1 = a.max.x - b.min.x;
    auto overlapX2 = b.max.x - a.min.x;
    auto overlapY1 = a.max.y - b.min.y;
    auto overlapY2 = b.max.y - a.min.y;
    auto overlapZ1 = a.max.z - b.min.z;
    auto overlapZ2 = b.max.z - a.min.z;
    
    // Find minimum overlap axis
    auto minOverlapX = (overlapX1 < overlapX2) ? overlapX1 : overlapX2;
    auto minOverlapY = (overlapY1 < overlapY2) ? overlapY1 : overlapY2;
    auto minOverlapZ = (overlapZ1 < overlapZ2) ? overlapZ1 : overlapZ2;
    
    // Constants for normals
    const FP zero(0);
    const FP one(1);
    const FP negOne(-1);
    
    // Determine separation axis (axis with least penetration)
    if (minOverlapX <= minOverlapY && minOverlapX <= minOverlapZ) {
        penetration = minOverlapX;
        normal = psyqo::Vec3{(overlapX1 < overlapX2) ? negOne : one, zero, zero};
    } else if (minOverlapY <= minOverlapZ) {
        penetration = minOverlapY;
        normal = psyqo::Vec3{zero, (overlapY1 < overlapY2) ? negOne : one, zero};
    } else {
        penetration = minOverlapZ;
        normal = psyqo::Vec3{zero, zero, (overlapZ1 < overlapZ2) ? negOne : one};
    }
    
    return true;
}

void CollisionSystem::updateTriggerState(uint16_t triggerIndex, uint16_t otherIndex, bool isOverlapping) {
    // Look for existing pair
    for (int i = 0; i < m_triggerPairCount; i++) {
        TriggerPair& pair = m_triggerPairs[i];
        if (pair.triggerIndex == triggerIndex && pair.otherIndex == otherIndex) {
            if (isOverlapping) {
                pair.framesSinceContact = 0;
                if (pair.state == 0) {
                    pair.state = 1; // Now staying
                }
            }
            return;
        }
    }
    
    // New pair - add it
    if (isOverlapping && m_triggerPairCount < MAX_TRIGGERS) {
        TriggerPair& pair = m_triggerPairs[m_triggerPairCount++];
        pair.triggerIndex = triggerIndex;
        pair.otherIndex = otherIndex;
        pair.framesSinceContact = 0;
        pair.state = 0; // New (enter event)
    }
}

bool CollisionSystem::areColliding(uint16_t indexA, uint16_t indexB) const {
    for (int i = 0; i < m_resultCount; i++) {
        if ((m_results[i].objectA == indexA && m_results[i].objectB == indexB) ||
            (m_results[i].objectA == indexB && m_results[i].objectB == indexA)) {
            return true;
        }
    }
    return false;
}

bool CollisionSystem::raycast(const psyqo::Vec3& origin, const psyqo::Vec3& direction,
                               psyqo::FixedPoint<12> maxDistance,
                               psyqo::Vec3& hitPoint, psyqo::Vec3& hitNormal,
                               uint16_t& hitObjectIndex) const {
    // Simple brute-force raycast against all colliders
    // TODO: Use spatial grid for optimization
    
    auto closestT = maxDistance;
    bool hit = false;
    
    // Fixed-point constants
    const FP zero(0);
    const FP one(1);
    const FP negOne(-1);
    const FP largeVal(1000);
    const FP negLargeVal(-1000);
    FP epsilon;
    epsilon.value = 4; // ~0.001 in 20.12 fixed point
    
    for (int i = 0; i < m_colliderCount; i++) {
        const CollisionData& collider = m_colliders[i];
        if (collider.type == CollisionType::None) continue;
        
        // Ray-AABB intersection test (slab method)
        const AABB& box = collider.bounds;
        
        auto tMin = negLargeVal;
        auto tMax = largeVal;
        
        // X slab
        if (direction.x != zero) {
            auto invD = one / direction.x;
            auto t1 = (box.min.x - origin.x) * invD;
            auto t2 = (box.max.x - origin.x) * invD;
            if (t1 > t2) { auto tmp = t1; t1 = t2; t2 = tmp; }
            if (t1 > tMin) tMin = t1;
            if (t2 < tMax) tMax = t2;
        } else if (origin.x < box.min.x || origin.x > box.max.x) {
            continue;
        }
        
        // Y slab
        if (direction.y != zero) {
            auto invD = one / direction.y;
            auto t1 = (box.min.y - origin.y) * invD;
            auto t2 = (box.max.y - origin.y) * invD;
            if (t1 > t2) { auto tmp = t1; t1 = t2; t2 = tmp; }
            if (t1 > tMin) tMin = t1;
            if (t2 < tMax) tMax = t2;
        } else if (origin.y < box.min.y || origin.y > box.max.y) {
            continue;
        }
        
        // Z slab
        if (direction.z != zero) {
            auto invD = one / direction.z;
            auto t1 = (box.min.z - origin.z) * invD;
            auto t2 = (box.max.z - origin.z) * invD;
            if (t1 > t2) { auto tmp = t1; t1 = t2; t2 = tmp; }
            if (t1 > tMin) tMin = t1;
            if (t2 < tMax) tMax = t2;
        } else if (origin.z < box.min.z || origin.z > box.max.z) {
            continue;
        }
        
        if (tMin > tMax || tMax < zero) continue;
        
        auto t = (tMin >= zero) ? tMin : tMax;
        
        if (t < closestT && t >= zero) {
            closestT = t;
            hitObjectIndex = collider.gameObjectIndex;
            hit = true;
            
            // Calculate hit point
            hitPoint = psyqo::Vec3{
                origin.x + direction.x * t,
                origin.y + direction.y * t,
                origin.z + direction.z * t
            };
            
            // Calculate normal (which face was hit)
            if ((hitPoint.x - box.min.x).abs() < epsilon) hitNormal = psyqo::Vec3{negOne, zero, zero};
            else if ((hitPoint.x - box.max.x).abs() < epsilon) hitNormal = psyqo::Vec3{one, zero, zero};
            else if ((hitPoint.y - box.min.y).abs() < epsilon) hitNormal = psyqo::Vec3{zero, negOne, zero};
            else if ((hitPoint.y - box.max.y).abs() < epsilon) hitNormal = psyqo::Vec3{zero, one, zero};
            else if ((hitPoint.z - box.min.z).abs() < epsilon) hitNormal = psyqo::Vec3{zero, zero, negOne};
            else hitNormal = psyqo::Vec3{zero, zero, one};
        }
    }
    
    return hit;
}

void CollisionSystem::processTriggerEvents(SceneManager& scene) {
    // Process trigger pairs and fire Lua events
    int writeIndex = 0;
    
    for (int i = 0; i < m_triggerPairCount; i++) {
        TriggerPair& pair = m_triggerPairs[i];
        
        // Get game object indices
        uint16_t triggerObjIdx = m_colliders[pair.triggerIndex].gameObjectIndex;
        uint16_t otherObjIdx = m_colliders[pair.otherIndex].gameObjectIndex;
        
        switch (pair.state) {
            case 0: // Enter
                scene.fireTriggerEnter(triggerObjIdx, otherObjIdx);
                pair.state = 1; // Move to staying
                m_triggerPairs[writeIndex++] = pair;
                break;
                
            case 1: // Staying
                scene.fireTriggerStay(triggerObjIdx, otherObjIdx);
                m_triggerPairs[writeIndex++] = pair;
                break;
                
            case 2: // Exit
                scene.fireTriggerExit(triggerObjIdx, otherObjIdx);
                // Don't copy - remove from list
                break;
        }
    }
    
    m_triggerPairCount = writeIndex;
}

} // namespace psxsplash