/**
 * 子站启停的受理语义：START立即激活，STOP立即停用并等待确认。
 * CON是发送任务，完成时不回写启停状态；后到START可结束尚未生成CON的停止等待。
 * 已生成的CON始终按FIFO完成；不暂存相反方向ACT，不重置序号，所有调用串行。
 */
#include "IEC104_Link_Slave_StartStop.h"
#include "IEC104_Link_Internal.h"

#include <stddef.h>

/* 调用方先预留发送空间；OK受理START并生成一帧CON，非法输入不修改状态。 */
IEC104_LinkResult_t IEC104_Link_Handle_Startdt_Act(
    IEC104_LinkState_t *state, const IEC104_ApciInfo_t *apci,
    uint8_t *response, uint16_t capacity)
{
    if (response == NULL || capacity < IEC104_APCI_LEN ||
        !IEC104_Link_Role_Valid_Internal(state, IEC104_ROLE_CONTROLLED) ||
        apci == NULL || apci->frame_type != IEC104_FRAME_TYPE_U ||
        apci->u_function != IEC104_U_STARTDT_ACT) {
        return IEC104_LINK_RESULT_FATAL;
    }
    (void)IEC104_Build_Uframe(response, IEC104_U_STARTDT_CON);
    state->dt_state = IEC104_DT_STARTED;
    state->dt_procedure = IEC104_DT_PROC_IDLE;
    return IEC104_LINK_RESULT_OK;
}

/* CON可能属于后续STOP之前的请求；完成不能重新激活链路。 */
IEC104_LinkResult_t IEC104_Link_Complete_Startdt_Con_Send(
    IEC104_LinkState_t *state, int sent_len)
{
    return IEC104_Link_Role_Valid_Internal(state, IEC104_ROLE_CONTROLLED) &&
           sent_len == IEC104_APCI_LEN ? IEC104_LINK_RESULT_OK : IEC104_LINK_RESULT_FATAL;
}

/* 首个START_CON是否已写出不影响STOP受理；排空中的重复STOP不重启期限。 */
IEC104_LinkResult_t IEC104_Link_Handle_Stopdt_Act(
    IEC104_LinkState_t *state, const IEC104_ApciInfo_t *apci)
{
    if (!IEC104_Link_Role_Valid_Internal(state, IEC104_ROLE_CONTROLLED) ||
        apci == NULL || apci->frame_type != IEC104_FRAME_TYPE_U ||
        apci->u_function != IEC104_U_STOPDT_ACT) {
        return IEC104_LINK_RESULT_FATAL;
    }
    if (state->dt_procedure == IEC104_DT_PROC_STOP_DRAINING) {
        return IEC104_LINK_RESULT_IGNORED;
    }
    state->dt_state = IEC104_DT_STOPPED;
    state->dt_procedure = IEC104_DT_PROC_STOP_DRAINING;
    return IEC104_LINK_RESULT_OK;
}

/* 覆盖全部接收数据的在途S已在FIFO中，可以先于CON排队，无须等实际写完。 */
static IEC104_StopdtPrepareResult_t Stopdt_Response_Status(const IEC104_LinkState_t *state)
{
    if (state->dt_procedure != IEC104_DT_PROC_STOP_DRAINING) {
        return IEC104_STOPDT_NOT_ACTIVE;
    }
    if (state->s_ack_state == IEC104_S_ACK_SEND_PENDING) {
        if (state->s_ack_nr != state->vr) {
            return IEC104_STOPDT_WAIT_SEND;
        }
    } else if (IEC104_Link_Unconfirmed_Rx_Internal(state) > 0U) {
        return IEC104_STOPDT_FRAME_READY;
    }
    return state->va != state->vs ? IEC104_STOPDT_WAIT_PEER_ACK : IEC104_STOPDT_FRAME_READY;
}

int IEC104_Link_Can_Prepare_Stopdt_Response(const IEC104_LinkState_t *state)
{
    if (!IEC104_Link_Role_Valid_Internal(state, IEC104_ROLE_CONTROLLED)) {
        return -1;
    }
    return Stopdt_Response_Status(state) == IEC104_STOPDT_FRAME_READY;
}

/* 先排S确认，全部已预留I帧获ACK后排STOP_CON；生成CON即结束协议排空状态。 */
IEC104_StopdtPrepareResult_t IEC104_Link_Prepare_Stopdt_Response(
    IEC104_LinkState_t *state, uint8_t *response, uint16_t capacity,
    IEC104_StopdtTx_t *tx)
{
    IEC104_StopdtPrepareResult_t readiness;
    if (!IEC104_Link_Role_Valid_Internal(state, IEC104_ROLE_CONTROLLED) || response == NULL ||
        capacity < IEC104_APCI_LEN || tx == NULL) {
        return IEC104_STOPDT_PREPARE_ERROR;
    }
    readiness = Stopdt_Response_Status(state);
    if (readiness != IEC104_STOPDT_FRAME_READY) {
        return readiness;
    }
    if (state->s_ack_state == IEC104_S_ACK_IDLE && IEC104_Link_Unconfirmed_Rx_Internal(state) > 0U) {
        if (IEC104_Link_Prepare_S_Ack_Internal(state, response, state->vr) != IEC104_APCI_LEN) {
            return IEC104_STOPDT_PREPARE_ERROR;
        }
        tx->frame_type = IEC104_STOPDT_FRAME_S_ACK;
    } else {
        (void)IEC104_Build_Uframe(response, IEC104_U_STOPDT_CON);
        state->dt_procedure = IEC104_DT_PROC_IDLE;
        tx->frame_type = IEC104_STOPDT_FRAME_CON;
    }
    tx->frame_length = IEC104_APCI_LEN;
    return IEC104_STOPDT_FRAME_READY;
}

/* 后到START可以已经激活链路，旧STOP_CON完成不得覆盖它。 */
IEC104_LinkResult_t IEC104_Link_Complete_Stopdt_Con_Send(
    IEC104_LinkState_t *state, int sent_len)
{
    return IEC104_Link_Role_Valid_Internal(state, IEC104_ROLE_CONTROLLED) &&
           sent_len == IEC104_APCI_LEN ? IEC104_LINK_RESULT_OK : IEC104_LINK_RESULT_FATAL;
}