// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2023 Red Hat
 */

#include "admin-state.h"

#include "logger.h"
#include "memory-alloc.h"
#include "permassert.h"

#include "completion.h"
#include "types.h"

static const struct admin_state_code VDO_CODE_NORMAL_OPERATION = {
        .name = "VDO_ADMIN_STATE_NORMAL_OPERATION",
        .normal = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_NORMAL_OPERATION = &VDO_CODE_NORMAL_OPERATION;
static const struct admin_state_code VDO_CODE_OPERATING = {
        .name = "VDO_ADMIN_STATE_OPERATING",
        .normal = true,
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_OPERATING = &VDO_CODE_OPERATING;
static const struct admin_state_code VDO_CODE_FORMATTING = {
        .name = "VDO_ADMIN_STATE_FORMATTING",
        .operating = true,
        .loading = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_FORMATTING = &VDO_CODE_FORMATTING;
static const struct admin_state_code VDO_CODE_PRE_LOADING = {
        .name = "VDO_ADMIN_STATE_PRE_LOADING",
        .operating = true,
        .loading = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_PRE_LOADING = &VDO_CODE_PRE_LOADING;
static const struct admin_state_code VDO_CODE_PRE_LOADED = {
        .name = "VDO_ADMIN_STATE_PRE_LOADED",
};
const struct admin_state_code *VDO_ADMIN_STATE_PRE_LOADED = &VDO_CODE_PRE_LOADED;
static const struct admin_state_code VDO_CODE_LOADING = {
        .name = "VDO_ADMIN_STATE_LOADING",
        .normal = true,
        .operating = true,
        .loading = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_LOADING = &VDO_CODE_LOADING;
static const struct admin_state_code VDO_CODE_LOADING_FOR_RECOVERY = {
        .name = "VDO_ADMIN_STATE_LOADING_FOR_RECOVERY",
        .operating = true,
        .loading = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_LOADING_FOR_RECOVERY =
        &VDO_CODE_LOADING_FOR_RECOVERY;
static const struct admin_state_code VDO_CODE_LOADING_FOR_REBUILD = {
        .name = "VDO_ADMIN_STATE_LOADING_FOR_REBUILD",
        .operating = true,
        .loading = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_LOADING_FOR_REBUILD = &VDO_CODE_LOADING_FOR_REBUILD;
static const struct admin_state_code VDO_CODE_WAITING_FOR_RECOVERY = {
        .name = "VDO_ADMIN_STATE_WAITING_FOR_RECOVERY",
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_WAITING_FOR_RECOVERY =
        &VDO_CODE_WAITING_FOR_RECOVERY;
static const struct admin_state_code VDO_CODE_NEW = {
        .name = "VDO_ADMIN_STATE_NEW",
        .quiescent = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_NEW = &VDO_CODE_NEW;
static const struct admin_state_code VDO_CODE_INITIALIZED = {
        .name = "VDO_ADMIN_STATE_INITIALIZED",
};
const struct admin_state_code *VDO_ADMIN_STATE_INITIALIZED = &VDO_CODE_INITIALIZED;
static const struct admin_state_code VDO_CODE_RECOVERING = {
        .name = "VDO_ADMIN_STATE_RECOVERING",
        .draining = true,
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_RECOVERING = &VDO_CODE_RECOVERING;
static const struct admin_state_code VDO_CODE_REBUILDING = {
        .name = "VDO_ADMIN_STATE_REBUILDING",
        .draining = true,
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_REBUILDING = &VDO_CODE_REBUILDING;
static const struct admin_state_code VDO_CODE_SAVING = {
        .name = "VDO_ADMIN_STATE_SAVING",
        .draining = true,
        .quiescing = true,
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_SAVING = &VDO_CODE_SAVING;
static const struct admin_state_code VDO_CODE_SAVED = {
        .name = "VDO_ADMIN_STATE_SAVED",
        .quiescent = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_SAVED = &VDO_CODE_SAVED;
static const struct admin_state_code VDO_CODE_SCRUBBING = {
        .name = "VDO_ADMIN_STATE_SCRUBBING",
        .draining = true,
        .loading = true,
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_SCRUBBING = &VDO_CODE_SCRUBBING;
static const struct admin_state_code VDO_CODE_SAVE_FOR_SCRUBBING = {
        .name = "VDO_ADMIN_STATE_SAVE_FOR_SCRUBBING",
        .draining = true,
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_SAVE_FOR_SCRUBBING = &VDO_CODE_SAVE_FOR_SCRUBBING;
static const struct admin_state_code VDO_CODE_STOPPING = {
        .name = "VDO_ADMIN_STATE_STOPPING",
        .draining = true,
        .quiescing = true,
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_STOPPING = &VDO_CODE_STOPPING;
static const struct admin_state_code VDO_CODE_STOPPED = {
        .name = "VDO_ADMIN_STATE_STOPPED",
        .quiescent = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_STOPPED = &VDO_CODE_STOPPED;
static const struct admin_state_code VDO_CODE_SUSPENDING = {
        .name = "VDO_ADMIN_STATE_SUSPENDING",
        .draining = true,
        .quiescing = true,
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_SUSPENDING = &VDO_CODE_SUSPENDING;
static const struct admin_state_code VDO_CODE_SUSPENDED = {
        .name = "VDO_ADMIN_STATE_SUSPENDED",
        .quiescent = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_SUSPENDED = &VDO_CODE_SUSPENDED;
static const struct admin_state_code VDO_CODE_SUSPENDED_OPERATION = {
        .name = "VDO_ADMIN_STATE_SUSPENDED_OPERATION",
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_SUSPENDED_OPERATION = &VDO_CODE_SUSPENDED_OPERATION;
static const struct admin_state_code VDO_CODE_RESUMING = {
        .name = "VDO_ADMIN_STATE_RESUMING",
        .operating = true,
};
const struct admin_state_code *VDO_ADMIN_STATE_RESUMING = &VDO_CODE_RESUMING;

/**
 * get_next_state() - Determine the state which should be set after a given operation completes
 *                    based on the operation and the current state.
 * @state: The current admin state.
 * @operation: The operation to be started.
 *
 * Return: The state to set when the operation completes or NULL if the operation can not be
 *         started in the current state.
 */
static const struct admin_state_code *get_next_state(const struct admin_state *state,
                                                     const struct admin_state_code *operation)
{
        const struct admin_state_code *code = vdo_get_admin_state_code(state);

        if (code->operating)
                return NULL;

        if (operation == VDO_ADMIN_STATE_SAVING)
                return (code == VDO_ADMIN_STATE_NORMAL_OPERATION ? VDO_ADMIN_STATE_SAVED : NULL);

        if (operation == VDO_ADMIN_STATE_SUSPENDING) {
                return (code == VDO_ADMIN_STATE_NORMAL_OPERATION
                        ? VDO_ADMIN_STATE_SUSPENDED
                        : NULL);
        }

        if (operation == VDO_ADMIN_STATE_STOPPING)
                return (code == VDO_ADMIN_STATE_NORMAL_OPERATION ? VDO_ADMIN_STATE_STOPPED : NULL);

        if (operation == VDO_ADMIN_STATE_PRE_LOADING)
                return (code == VDO_ADMIN_STATE_INITIALIZED ? VDO_ADMIN_STATE_PRE_LOADED : NULL);

        if (operation == VDO_ADMIN_STATE_SUSPENDED_OPERATION) {
                return (((code == VDO_ADMIN_STATE_SUSPENDED) ||
                         (code == VDO_ADMIN_STATE_SAVED)) ? code : NULL);
        }

        return VDO_ADMIN_STATE_NORMAL_OPERATION;
}

/**
 * vdo_finish_operation() - Finish the current operation.
 * @state: The current admin state.
 * @result: The result of the operation.
 *
 * Will notify the operation waiter if there is one. This method should be used for operations
 * started with vdo_start_operation(). For operations which were started with vdo_start_draining(),
 * use vdo_finish_draining() instead.
 *
 * Return: true if there was an operation to finish.
 */
bool vdo_finish_operation(struct admin_state *state, int result)
{
        if (!vdo_get_admin_state_code(state)->operating)
                return false;

        state->complete = state->starting;
        if (state->waiter != NULL)
                vdo_set_completion_result(state->waiter, result);

        if (!state->starting) {
                vdo_set_admin_state_code(state, state->next_state);
                if (state->waiter != NULL)
                        vdo_launch_completion(vdo_forget(state->waiter));
        }

        return true;
}

/**
 * begin_operation() - Begin an operation if it may be started given the current state.
 * @state: The current admin state.
 * @operation: The operation to be started.
 * @waiter: A completion to notify when the operation is complete; may be NULL.
 * @initiator: The vdo_admin_initiator_fn to call if the operation may begin; may be NULL.
 *
 * Return: VDO_SUCCESS or an error.
 */
static int __must_check begin_operation(struct admin_state *state,
                                        const struct admin_state_code *operation,
                                        struct vdo_completion *waiter,
                                        vdo_admin_initiator_fn initiator)
{
        int result;
        const struct admin_state_code *next_state = get_next_state(state, operation);

        if (next_state == NULL) {
                result = vdo_log_error_strerror(VDO_INVALID_ADMIN_STATE,
                                                "Can't start %s from %s",
                                                operation->name,
                                                vdo_get_admin_state_code(state)->name);
        } else if (state->waiter != NULL) {
                result = vdo_log_error_strerror(VDO_COMPONENT_BUSY,
                                                "Can't start %s with extant waiter",
                                                operation->name);
        } else {
                state->waiter = waiter;
                state->next_state = next_state;
                vdo_set_admin_state_code(state, operation);
                if (initiator != NULL) {
                        state->starting = true;
                        initiator(state);
                        state->starting = false;
                        if (state->complete)
                                vdo_finish_operation(state, VDO_SUCCESS);
                }

                return VDO_SUCCESS;
        }

        if (waiter != NULL)
                vdo_continue_completion(waiter, result);

        return result;
}

/**
 * start_operation() - Start an operation if it may be started given the current state.
 * @state: The current admin state.
 * @operation: The operation to be started.
 * @waiter: A completion to notify when the operation is complete; may be NULL.
 * @initiator: The vdo_admin_initiator_fn to call if the operation may begin; may be NULL.
 *
 * Return: true if the operation was started.
 */
static inline bool __must_check start_operation(struct admin_state *state,
                                                const struct admin_state_code *operation,
                                                struct vdo_completion *waiter,
                                                vdo_admin_initiator_fn initiator)
{
        return (begin_operation(state, operation, waiter, initiator) == VDO_SUCCESS);
}

/**
 * check_code() - Check the result of a state validation.
 * @valid: True if the code is of an appropriate type.
 * @code: The code which failed to be of the correct type.
 * @what: What the code failed to be, for logging.
 * @waiter: The completion to notify of the error; may be NULL.
 *
 * If the result failed, log an invalid state error and, if there is a waiter, notify it.
 *
 * Return: The result of the check.
 */
static bool check_code(bool valid, const struct admin_state_code *code, const char *what,
                       struct vdo_completion *waiter)
{
        int result;

        if (valid)
                return true;

        result = vdo_log_error_strerror(VDO_INVALID_ADMIN_STATE,
                                        "%s is not a %s", code->name, what);
        if (waiter != NULL)
                vdo_continue_completion(waiter, result);

        return false;
}

/**
 * assert_vdo_drain_operation() - Check that an operation is a drain.
 * @operation: The operation to check.
 * @waiter: The completion to finish with an error if the operation is not a drain.
 *
 * Return: true if the specified operation is a drain.
 */
static bool __must_check assert_vdo_drain_operation(const struct admin_state_code *operation,
                                                    struct vdo_completion *waiter)
{
        return check_code(operation->draining, operation, "drain operation", waiter);
}

/**
 * vdo_start_draining() - Initiate a drain operation if the current state permits it.
 * @state: The current admin state.
 * @operation: The type of drain to initiate.
 * @waiter: The completion to notify when the drain is complete.
 * @initiator: The vdo_admin_initiator_fn to call if the operation may begin; may be NULL.
 *
 * Return: true if the drain was initiated, if not the waiter will be notified.
 */
bool vdo_start_draining(struct admin_state *state,
                        const struct admin_state_code *operation,
                        struct vdo_completion *waiter, vdo_admin_initiator_fn initiator)
{
        const struct admin_state_code *code = vdo_get_admin_state_code(state);

        if (!assert_vdo_drain_operation(operation, waiter))
                return false;

        if (code->quiescent) {
                vdo_launch_completion(waiter);
                return false;
        }

        if (!code->normal) {
                vdo_log_error_strerror(VDO_INVALID_ADMIN_STATE, "can't start %s from %s",
                                       operation->name, code->name);
                vdo_continue_completion(waiter, VDO_INVALID_ADMIN_STATE);
                return false;
        }

        return start_operation(state, operation, waiter, initiator);
}

/**
 * vdo_finish_draining() - Finish a drain operation if one was in progress.
 * @state: The current admin state.
 *
 * Return: true if the state was draining; will notify the waiter if so.
 */
bool vdo_finish_draining(struct admin_state *state)
{
        return vdo_finish_draining_with_result(state, VDO_SUCCESS);
}

/**
 * vdo_finish_draining_with_result() - Finish a drain operation with a status code.
 * @state: The current admin state.
 * @result: The result of the drain operation.
 *
 * Return: true if the state was draining; will notify the waiter if so.
 */
bool vdo_finish_draining_with_result(struct admin_state *state, int result)
{
        return (vdo_is_state_draining(state) && vdo_finish_operation(state, result));
}

/**
 * vdo_assert_load_operation() - Check that an operation is a load.
 * @operation: The operation to check.
 * @waiter: The completion to finish with an error if the operation is not a load.
 *
 * Return: true if the specified operation is a load.
 */
bool vdo_assert_load_operation(const struct admin_state_code *operation,
                               struct vdo_completion *waiter)
{
        return check_code(operation->loading, operation, "load operation", waiter);
}

/**
 * vdo_start_loading() - Initiate a load operation if the current state permits it.
 * @state: The current admin state.
 * @operation: The type of load to initiate.
 * @waiter: The completion to notify when the load is complete; may be NULL.
 * @initiator: The vdo_admin_initiator_fn to call if the operation may begin; may be NULL.
 *
 * Return: true if the load was initiated, if not the waiter will be notified.
 */
bool vdo_start_loading(struct admin_state *state,
                       const struct admin_state_code *operation,
                       struct vdo_completion *waiter, vdo_admin_initiator_fn initiator)
{
        return (vdo_assert_load_operation(operation, waiter) &&
                start_operation(state, operation, waiter, initiator));
}

/**
 * vdo_finish_loading() - Finish a load operation if one was in progress.
 * @state: The current admin state.
 *
 * Return: true if the state was loading; will notify the waiter if so.
 */
bool vdo_finish_loading(struct admin_state *state)
{
        return vdo_finish_loading_with_result(state, VDO_SUCCESS);
}

/**
 * vdo_finish_loading_with_result() - Finish a load operation with a status code.
 * @state: The current admin state.
 * @result: The result of the load operation.
 *
 * Return: true if the state was loading; will notify the waiter if so.
 */
bool vdo_finish_loading_with_result(struct admin_state *state, int result)
{
        return (vdo_is_state_loading(state) && vdo_finish_operation(state, result));
}

/**
 * assert_vdo_resume_operation() - Check whether an admin_state_code is a resume operation.
 * @operation: The operation to check.
 * @waiter: The completion to notify if the operation is not a resume operation; may be NULL.
 *
 * Return: true if the code is a resume operation.
 */
static bool __must_check assert_vdo_resume_operation(const struct admin_state_code *operation,
                                                     struct vdo_completion *waiter)
{
        return check_code(operation == VDO_ADMIN_STATE_RESUMING, operation,
                          "resume operation", waiter);
}

/**
 * vdo_start_resuming() - Initiate a resume operation if the current state permits it.
 * @state: The current admin state.
 * @operation: The type of resume to start.
 * @waiter: The completion to notify when the resume is complete; may be NULL.
 * @initiator: The vdo_admin_initiator_fn to call if the operation may begin; may be NULL.
 *
 * Return: true if the resume was initiated, if not the waiter will be notified.
 */
bool vdo_start_resuming(struct admin_state *state,
                        const struct admin_state_code *operation,
                        struct vdo_completion *waiter, vdo_admin_initiator_fn initiator)
{
        return (assert_vdo_resume_operation(operation, waiter) &&
                start_operation(state, operation, waiter, initiator));
}

/**
 * vdo_finish_resuming() - Finish a resume operation if one was in progress.
 * @state: The current admin state.
 *
 * Return: true if the state was resuming; will notify the waiter if so.
 */
bool vdo_finish_resuming(struct admin_state *state)
{
        return vdo_finish_resuming_with_result(state, VDO_SUCCESS);
}

/**
 * vdo_finish_resuming_with_result() - Finish a resume operation with a status code.
 * @state: The current admin state.
 * @result: The result of the resume operation.
 *
 * Return: true if the state was resuming; will notify the waiter if so.
 */
bool vdo_finish_resuming_with_result(struct admin_state *state, int result)
{
        return (vdo_is_state_resuming(state) && vdo_finish_operation(state, result));
}

/**
 * vdo_resume_if_quiescent() - Change the state to normal operation if the current state is
 *                             quiescent.
 * @state: The current admin state.
 *
 * Return: VDO_SUCCESS if the state resumed, VDO_INVALID_ADMIN_STATE otherwise.
 */
int vdo_resume_if_quiescent(struct admin_state *state)
{
        if (!vdo_is_state_quiescent(state))
                return VDO_INVALID_ADMIN_STATE;

        vdo_set_admin_state_code(state, VDO_ADMIN_STATE_NORMAL_OPERATION);
        return VDO_SUCCESS;
}

/**
 * vdo_start_operation() - Attempt to start an operation.
 * @state: The current admin state.
 * @operation: The operation to attempt to start.
 *
 * Return: VDO_SUCCESS if the operation was started, VDO_INVALID_ADMIN_STATE if not
 */
int vdo_start_operation(struct admin_state *state,
                        const struct admin_state_code *operation)
{
        return vdo_start_operation_with_waiter(state, operation, NULL, NULL);
}

/**
 * vdo_start_operation_with_waiter() - Attempt to start an operation.
 * @state: The current admin state.
 * @operation: The operation to attempt to start.
 * @waiter: The completion to notify when the operation completes or fails to start; may be NULL.
 * @initiator: The vdo_admin_initiator_fn to call if the operation may begin; may be NULL.
 *
 * Return: VDO_SUCCESS if the operation was started, VDO_INVALID_ADMIN_STATE if not
 */
int vdo_start_operation_with_waiter(struct admin_state *state,
                                    const struct admin_state_code *operation,
                                    struct vdo_completion *waiter,
                                    vdo_admin_initiator_fn initiator)
{
        return (check_code(operation->operating, operation, "operation", waiter) ?
                begin_operation(state, operation, waiter, initiator) :
                VDO_INVALID_ADMIN_STATE);
}