// libbravais public api header file

#ifndef BRAVAIS_H
#define BRAVAIS_H

#include <stddef.h>
#include <stdint.h>

#include "bravais/export.h" // Generated by cmake

#ifdef __cplusplus
extern "C" {
#endif

#define BRAVAIS_VERSION_MAJOR 0
#define BRAVAIS_VERSION_MINOR 1
#define BRAVAIS_VERSION_PATCH 0
#define BRAVAIS_VERSION ((BRAVAIS_VERSION_MAJOR << 16) | (BRAVAIS_VERSION_MINOR << 8) | BRAVAIS_VERSION_PATCH)

#define BRAVAIS_NO_TIMEOUT UINT64_MAX

typedef enum {
    // Error codes; Generally <0 = error, 0 = success
    BRAVAIS_EMPTY = 1, // Nothing to emit right now
    BRAVAIS_OK = 0,
    BRAVAIS_ERR_INVALID_ARG = -1,
    BRAVAIS_ERR_BUFFER_TOO_SMALL = -2,
    BRAVAIS_ERR_MALFORMED = -3,
    BRAVAIS_ERR_OUT_OF_MEMORY = -4,
    BRAVAIS_ERR_UNSUPPORTED = -5,

    BRAVAIS_ERR_UNKNOWN = -1000
} bravais_result_t;

typedef enum {
    BRAVAIS_ROLE_INITIATOR,
    BRAVAIS_ROLE_RESPONDER
} bravais_role_t;

typedef enum {
    BRAVAIS_TRANSPORT_MODE_RAW,
    BRAVAIS_TRANSPORT_MODE_QUIC
} bravais_transport_mode_t;

typedef enum {
    BRAVAIS_LOG_LEVEL_DEBUG,
    BRAVAIS_LOG_LEVEL_INFO,
    BRAVAIS_LOG_LEVEL_WARN,
    BRAVAIS_LOG_LEVEL_ERROR
} bravais_log_level_t;

/**
 * @brief Logging callback function type
 * @param userData User-defined data passed to the logging function
 * @param level The log level of the message
 * @param message The log message string
 */
typedef void (*bravais_log_fn_t)(void* userData, bravais_log_level_t level, const char* message);

typedef struct {
    bravais_role_t role;
    bravais_transport_mode_t transportMode;
    bravais_log_fn_t logFn;
    void* logUserData;

    // TODO: Add more configuration options here as needed
} bravais_config_t;

typedef struct bravais_conn bravais_conn_t; // Opaque connection type

// =============================================================================
// Public API functions
// =============================================================================

/**
 * @brief Runtime library version number, packed as (major << 16) | (minor << 8) | patch
 * @return The version number, packed as (major << 16) | (minor << 8) | patch
 */
BRAVAIS_API uint32_t bravais_version(void);

/**
 * @brief Initialize the config struct with defaults for all optional fields.
 * @param config Pointer to a bravais_config_t struct to initialize.
 * @return BRAVAIS_OK on success, or BRAVAIS_ERR_INVALID_ARG if the config pointer is NULL.
 * @attention The caller must still set role and transportMode manually.
 */
BRAVAIS_API bravais_result_t bravais_config_init(const bravais_config_t* config);

/**
 * @brief Create a new connection.
 * @param config The configuration to use for the new connection.
 * @param outConn A pointer to a bravais_conn_t pointer that will be set to the new connection. Set to NULL on failure.
 * @return BRAVAIS_OK on success, BRAVAIS_ERR_INVALID_ARG, or BRAVAIS_ERR_OUT_OF_MEMORY.
 * @attention The config is copied. The caller may reuse or discard it afterwards.
 */
BRAVAIS_API bravais_result_t bravais_conn_create(const bravais_config_t* config, bravais_conn_t** outConn);

/**
 * @brief Destroy a connection.
 * @param conn The connection to destroy.
 * @attention NULL is a no-op.
 */
BRAVAIS_API void bravais_conn_destroy(bravais_conn_t* conn);

/**
 * @brief Feed one datagram received from the network.
 * @param conn The connection to feed the datagram to.
 * @param data The datagram data received from the network.
 * @param dataLen The length of the datagram data.
 * @param nowMs The current time in milliseconds (unix epoch).
 * @return BRAVAIS_OK on success, BRAVAIS_ERR_INVALID_ARG, or BRAVAIS_ERR_MALFORMED (datagram is malformed).
 * @attention Any resulting output is queued. Drain it with the poll functions.
 */
BRAVAIS_API bravais_result_t bravais_recv_datagram(bravais_conn_t* conn, const uint8_t* data, size_t dataLen, uint64_t nowMs);

/**
 * @brief Submit one plaintext packet read from the TUN device.
 * @param conn The connection to submit the packet to.
 * @param data The packet data read from the TUN device.
 * @param dataLen The length of the packet data.
 * @param nowMs The current time in milliseconds (unix epoch).
 * @return BRAVAIS_OK on success, or BRAVAIS_ERR_INVALID_ARG.
 * @attention The packet is encrypted and queued for sending. Drain it with bravais_poll_datagram().
 */
BRAVAIS_API bravais_result_t bravais_send_packet(bravais_conn_t* conn, const uint8_t* data, size_t dataLen, uint64_t nowMs);

/**
 * @brief Take the next datagram to send to the network, if any.
 * @param conn The connection to poll for datagrams.
 * @param out A buffer to write the datagram to.
 * @param outCap The capacity of the output buffer.
 * @param outLen A pointer to a size_t that will be set to the length of the datagram written to the output buffer.
 * @return BRAVAIS_OK on success, BRAVAIS_EMPTY if no datagram is available (this is NOT an error), or BRAVAIS_ERR_BUFFER_TOO_SMALL.
 * @attention The caller must provide a buffer large enough to hold the datagram.
 */
BRAVAIS_API bravais_result_t bravais_poll_datagram(bravais_conn_t* conn, uint8_t* out, size_t outCap, size_t* outLen);

/**
 * @brief Take the next decrypted packet to write to the TUN device, if any.
 * @param conn The connection to poll for packets.
 * @param out A buffer to write the packet to.
 * @param outCap The capacity of the output buffer.
 * @param outLen A pointer to a size_t that will be set to the length of the packet written to the output buffer.
 * @return BRAVAIS_OK on success, BRAVAIS_EMPTY if no packet is available (this is NOT an error), or BRAVAIS_ERR_BUFFER_TOO_SMALL.
 * @attention The caller must provide a buffer large enough to hold the packet.
 * @attention Same buffer semantics as bravais_poll_datagram().
 *
 */
BRAVAIS_API bravais_result_t bravais_poll_plaintext(bravais_conn_t* conn, uint8_t* out, size_t outCap, size_t* outLen);

/**
 * @brief Earliest time the connection needs bravais_on_timeout() called.
 * @return Absolute deadline in milliseconds (unix epoch) for the next timeout, or BRAVAIS_NO_TIMEOUT if no timeout is needed.
 */
BRAVAIS_API uint64_t bravais_get_next_timeout(bravais_conn_t* conn);

/**
 * @brief Run any timers due at nowMs.
 * @param conn The connection to run timers for.
 * @param nowMs The current time in milliseconds (unix epoch).
 * @return BRAVAIS_OK on success, or BRAVAIS_ERR_INVALID_ARG.
 * @attention Safe to call early. No-op if no timers are due yet.
 */
BRAVAIS_API bravais_result_t bravais_on_timeout(bravais_conn_t* conn, uint64_t nowMs);

#ifdef __cplusplus
}
#endif

#endif // BRAVAIS_H