thumbnail_service.h

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// BSD 3-Clause License
// Copyright (c) 2021-2025, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#pragma once
 
#include <chrono>
#include <cstdint>
#include <functional>
#include <memory>
#include <mutex>
#include <optional>
#include <shared_mutex>
#include <string>
#include <string_view>
#include <unordered_map>
#include <vector>
 
namespace kcenon::pacs::storage {
class index_database;
}  // namespace kcenon::pacs::storage
 
namespace kcenon::pacs::web {
 
struct thumbnail_params {
    uint16_t size{128};
 
    std::string format{"jpeg"};
 
    int quality{60};
 
    uint32_t frame{1};
};
 
struct thumbnail_cache_entry {
    std::vector<uint8_t> data;
 
    std::string content_type;
 
    std::chrono::system_clock::time_point created_at;
 
    std::chrono::system_clock::time_point last_accessed;
};
 
struct thumbnail_result {
    bool success{false};
 
    std::string error_message;
 
    thumbnail_cache_entry entry;
 
    static thumbnail_result ok(thumbnail_cache_entry entry) {
        thumbnail_result r;
        r.success = true;
        r.entry = std::move(entry);
        return r;
    }
 
    static thumbnail_result error(std::string message) {
        thumbnail_result r;
        r.success = false;
        r.error_message = std::move(message);
        return r;
    }
};
 
class thumbnail_service {
public:
    explicit thumbnail_service(
        std::shared_ptr<storage::index_database> database);
 
    ~thumbnail_service();
 
    thumbnail_service(const thumbnail_service&) = delete;
    thumbnail_service& operator=(const thumbnail_service&) = delete;
    thumbnail_service(thumbnail_service&&) = delete;
    thumbnail_service& operator=(thumbnail_service&&) = delete;
 
    // =========================================================================
    // Thumbnail Generation
    // =========================================================================
 
    [[nodiscard]] thumbnail_result get_thumbnail(
        std::string_view sop_instance_uid,
        const thumbnail_params& params);
 
    [[nodiscard]] thumbnail_result get_series_thumbnail(
        std::string_view series_uid,
        const thumbnail_params& params);
 
    [[nodiscard]] thumbnail_result get_study_thumbnail(
        std::string_view study_uid,
        const thumbnail_params& params);
 
    // =========================================================================
    // Cache Management
    // =========================================================================
 
    void clear_cache();
 
    void clear_cache(std::string_view sop_instance_uid);
 
    [[nodiscard]] size_t cache_size() const;
 
    [[nodiscard]] size_t cache_entry_count() const;
 
    void set_max_cache_size(size_t max_bytes);
 
    [[nodiscard]] size_t max_cache_size() const;
 
private:
    struct cache_key {
        std::string uid;
        uint16_t size;
        std::string format;
        int quality;
        uint32_t frame;
 
        bool operator==(const cache_key&) const = default;
    };
 
    struct cache_key_hash {
        size_t operator()(const cache_key& k) const {
            size_t h = std::hash<std::string>{}(k.uid);
            h ^= std::hash<uint16_t>{}(k.size) << 1;
            h ^= std::hash<std::string>{}(k.format) << 2;
            h ^= std::hash<int>{}(k.quality) << 3;
            h ^= std::hash<uint32_t>{}(k.frame) << 4;
            return h;
        }
    };
 
    std::shared_ptr<storage::index_database> database_;
 
    std::unordered_map<cache_key, thumbnail_cache_entry, cache_key_hash> cache_;
 
    mutable std::shared_mutex cache_mutex_;
 
    size_t current_cache_size_{0};
 
    size_t max_cache_size_{64 * 1024 * 1024};
 
    // =========================================================================
    // Internal Methods
    // =========================================================================
 
    [[nodiscard]] std::vector<uint8_t> generate_thumbnail(
        std::string_view file_path,
        const thumbnail_params& params);
 
    [[nodiscard]] std::optional<std::string> select_representative_instance(
        std::string_view series_uid);
 
    [[nodiscard]] std::optional<std::string> select_representative_series(
        std::string_view study_uid);
 
    void evict_lru();
 
    [[nodiscard]] static std::string get_content_type(std::string_view format);
};
 
}  // namespace kcenon::pacs::web