// priority_queue.cpp - C++ style but using C-style storage
#include "priority_queue.h"
#include "../../common/include/secure_mem.h"
#include <algorithm>
#include <cstring>

using fetchml::common::safe_strncpy;

PriorityQueueIndex::PriorityQueueIndex(const char* queue_dir)
    : heap_(entries_, EntryComparator{}) {
    // Initialize storage (returns false if path invalid, we ignore - open() will fail)
    storage_init(&storage_, queue_dir);
}

PriorityQueueIndex::~PriorityQueueIndex() {
    close();
}

bool PriorityQueueIndex::open() {
    if (!storage_open(&storage_)) {
        safe_strncpy(last_error_, "Failed to open storage", sizeof(last_error_));
        return false;
    }
    
    load_entries();
    rebuild_heap();
    return true;
}

void PriorityQueueIndex::close() {
    if (dirty_) {
        save();
    }
    storage_close(&storage_);
    storage_cleanup(&storage_);
    entries_.clear();
    heap_.clear();
}

void PriorityQueueIndex::load_entries() {
    entries_.clear();
    
    // Try memory-mapped access first
    if (storage_mmap_for_read(&storage_)) {
        size_t count = storage_mmap_entry_count(&storage_);
        const DiskEntry* disk_entries = storage_mmap_entries(&storage_);
        
        entries_.reserve(count);
        for (size_t i = 0; i < count; ++i) {
            IndexEntry entry;
            memcpy(&entry.task.id, disk_entries[i].id, 64);
            entry.task.id[63] = '\0';  // Ensure null termination
            memcpy(&entry.task.job_name, disk_entries[i].job_name, 128);
            entry.task.job_name[127] = '\0';  // Ensure null termination
            memcpy(&entry.task.status, disk_entries[i].status, 16);
            entry.task.status[15] = '\0';
            entry.task.priority = disk_entries[i].priority;
            entry.task.created_at = disk_entries[i].created_at;
            entry.task.next_retry = disk_entries[i].next_retry;
            entry.offset = i;
            entry.dirty = false;
            entries_.push_back(entry);
        }
    }
    storage_munmap(&storage_);
    
    // Rebuild ID index after loading
    rebuild_id_index();
}

void PriorityQueueIndex::rebuild_heap() {
    std::vector<size_t> queued_indices;
    
    for (size_t i = 0; i < entries_.size(); ++i) {
        queued_indices.push_back(i);
    }
    
    heap_.build(queued_indices);
}

void PriorityQueueIndex::rebuild_id_index() {
    id_index_.clear();
    id_index_.reserve(entries_.size());
    for (size_t i = 0; i < entries_.size(); ++i) {
        id_index_[entries_[i].task.id] = i;
    }
}

int PriorityQueueIndex::add_tasks(const qi_task_t* tasks, uint32_t count) {
    // Validate batch size to prevent integer overflow (CVE-2025-0838)
    if (!tasks || count == 0) return 0;
    if (count > MAX_BATCH_SIZE) {
        safe_strncpy(last_error_, "Batch size exceeds maximum", sizeof(last_error_));
        return -1;
    }
    
    std::lock_guard<std::mutex> lock(mutex_);
    
    for (uint32_t i = 0; i < count; ++i) {
        IndexEntry entry;
        entry.task = tasks[i];
        // Enforce null termination on all string fields
        entry.task.id[sizeof(entry.task.id) - 1] = '\0';
        entry.task.job_name[sizeof(entry.task.job_name) - 1] = '\0';
        entry.task.status[sizeof(entry.task.status) - 1] = '\0';
        entry.offset = 0;
        entry.dirty = true;
        entries_.push_back(entry);
    }
    
    dirty_ = true;
    rebuild_heap();
    return static_cast<int>(count);
}

int PriorityQueueIndex::get_next_batch(qi_task_t* out_tasks, uint32_t max_count, uint32_t* out_count) {
    std::lock_guard<std::mutex> lock(mutex_);
    
    uint32_t got = 0;
    
    while (got < max_count && !heap_.empty()) {
        size_t idx = heap_.pop();
        if (idx >= entries_.size()) continue;
        
        out_tasks[got] = entries_[idx].task;
        got++;
    }
    
    if (out_count) {
        *out_count = got;
    }
    
    return 0;
}

int PriorityQueueIndex::save() {
    std::lock_guard<std::mutex> lock(mutex_);
    
    // Convert entries to disk format
    std::vector<DiskEntry> disk_entries;
    disk_entries.reserve(entries_.size());
    
    for (const auto& entry : entries_) {
        DiskEntry disk;
        memcpy(disk.id, entry.task.id, 64);
        memcpy(disk.job_name, entry.task.job_name, 128);
        memcpy(disk.status, entry.task.status, 16);
        disk.priority = entry.task.priority;
        disk.created_at = entry.task.created_at;
        disk.next_retry = entry.task.next_retry;
        memset(disk.reserved, 0, sizeof(disk.reserved));
        disk_entries.push_back(disk);
    }
    
    if (!storage_write_entries(&storage_, disk_entries.data(), disk_entries.size())) {
        safe_strncpy(last_error_, "Failed to write entries", sizeof(last_error_));
        return -1;
    }
    
    dirty_ = false;
    return 0;
}

int PriorityQueueIndex::get_all_tasks(qi_task_t** out_tasks, size_t* out_count) {
    std::lock_guard<std::mutex> lock(mutex_);
    
    if (entries_.empty()) {
        *out_tasks = nullptr;
        *out_count = 0;
        return 0;
    }
    
    qi_task_t* tasks = new qi_task_t[entries_.size()];
    
    for (size_t i = 0; i < entries_.size(); ++i) {
        tasks[i] = entries_[i].task;
    }
    
    *out_tasks = tasks;
    *out_count = entries_.size();
    return 0;
}

// Get task by ID (O(1) lookup via hash map)
int PriorityQueueIndex::get_task_by_id(const char* task_id, qi_task_t* out_task) {
    std::lock_guard<std::mutex> lock(mutex_);
    
    if (!task_id || !out_task) return -1;
    
    auto it = id_index_.find(task_id);
    if (it == id_index_.end()) {
        safe_strncpy(last_error_, "Task not found", sizeof(last_error_));
        return -1;
    }
    
    *out_task = entries_[it->second].task;
    return 0;
}

// Update tasks
int PriorityQueueIndex::update_tasks(const qi_task_t* tasks, uint32_t count) {
    std::lock_guard<std::mutex> lock(mutex_);
    
    if (!tasks || count == 0) return -1;
    
    for (uint32_t i = 0; i < count; ++i) {
        auto it = id_index_.find(tasks[i].id);
        if (it != id_index_.end()) {
            entries_[it->second].task = tasks[i];
            // Enforce null termination on all string fields
            entries_[it->second].task.id[sizeof(entries_[it->second].task.id) - 1] = '\0';
            entries_[it->second].task.job_name[sizeof(entries_[it->second].task.job_name) - 1] = '\0';
            entries_[it->second].task.status[sizeof(entries_[it->second].task.status) - 1] = '\0';
            entries_[it->second].dirty = true;
        }
    }
    
    dirty_ = true;
    rebuild_heap();
    return static_cast<int>(count);
}

// Remove tasks
int PriorityQueueIndex::remove_tasks(const char** task_ids, uint32_t count) {
    std::lock_guard<std::mutex> lock(mutex_);
    
    if (!task_ids || count == 0) return -1;
    
    int removed = 0;
    for (uint32_t i = 0; i < count; ++i) {
        if (!task_ids[i]) continue;
        
        auto it = id_index_.find(task_ids[i]);
        if (it != id_index_.end()) {
            size_t idx = it->second;
            // Swap with last and pop (fast removal)
            if (idx < entries_.size() - 1) {
                entries_[idx] = entries_.back();
                id_index_[entries_[idx].task.id] = idx;
            }
            entries_.pop_back();
            id_index_.erase(it);
            removed++;
        }
    }
    
    if (removed > 0) {
        dirty_ = true;
        rebuild_heap();
    }
    
    return removed;
}

// Compact index (remove finished/failed tasks)
int PriorityQueueIndex::compact_index() {
    std::lock_guard<std::mutex> lock(mutex_);
    
    size_t original_size = entries_.size();
    
    // Remove entries with "finished" or "failed" status
    auto new_end = std::remove_if(entries_.begin(), entries_.end(),
        [](const IndexEntry& e) {
            return strcmp(e.task.status, "finished") == 0 ||
                   strcmp(e.task.status, "failed") == 0;
        });
    
    entries_.erase(new_end, entries_.end());
    
    if (entries_.size() < original_size) {
        dirty_ = true;
        rebuild_id_index();
        rebuild_heap();
    }
    
    return static_cast<int>(original_size - entries_.size());
}

// Rebuild heap
int PriorityQueueIndex::rebuild() {
    std::lock_guard<std::mutex> lock(mutex_);
    rebuild_heap();
    return 0;
}