#pragma once

#include "defines.h"

/** @brief A function pointer definition for jobs. */
typedef b8 (*pfn_job_start)(void *, void *);

/** @brief A function pointer definition for completion of a job. */
typedef void (*pfn_job_on_complete)(void *);

struct frame_data;

/** @brief Describes a type of job */
typedef enum job_type {
	/**
	 * @brief A general job that does not have any specific thread requirements.
	 * This means it matters little which job thread this job runs on.
	 */
	JOB_TYPE_GENERAL = 0x02,

	/**
	 * @brief A resource loading job. Resources should always load on the same thread
	 * to avoid potential disk thrashing.
	 */
	JOB_TYPE_RESOURCE_LOAD = 0x04,

	/**
	 * @brief Jobs using GPU resources should be bound to a thread using this job type. Multithreaded
	 * renderers will use a specific job thread, and this type of job will run on that thread.
	 * For single-threaded renderers, this will be on the main thread.
	 */
	JOB_TYPE_GPU_RESOURCE = 0x08,
} job_type;

/**
 * @brief Determines which job queue a job uses. The high-priority queue is always
 * exhausted first before processing the normal-priority queue, which must also
 * be exhausted before processing the low-priority queue.
 */
typedef enum job_priority {
	/** @brief The lowest-priority job, used for things that can wait to be done if need be, such as log flushing. */
	JOB_PRIORITY_LOW,
	/** @brief A normal-priority job. Should be used for medium-priority tasks such as loading assets. */
	JOB_PRIORITY_NORMAL,
	/** @brief The highest-priority job. Should be used sparingly, and only for time-critical operations.*/
	JOB_PRIORITY_HIGH
} job_priority;

/**
 * @brief Describes a job to be run.
 */
typedef struct job_info {
	/** @brief The type of job. Used to determine which thread the job executes on. */
	job_type type;

	/** @brief The uniquie identifier of this job. */
	u16 id;

	/** @brief The priority of this job. Higher priority jobs obviously run sooner. */
	job_priority priority;

	/** @brief A function pointer to be invoked when the job starts. Required. */
	pfn_job_start entry_point;

	/** @brief A function pointer to be invoked when the job successfully completes. Optional. */
	pfn_job_on_complete on_success;

	/** @brief A function pointer to be invoked when the job successfully fails. Optional. */
	pfn_job_on_complete on_fail;

	/** @brief Data to be passed to the entry point upon execution. */
	void *param_data;

	/** @brief The size of the data passed to the job. */
	u32 param_data_size;

	/** @brief Data to be passed to the success/fail function upon execution, if exists. */
	void *result_data;

	/** @brief The size of the data passed to the success/fail function. */
	u32 result_data_size;

	/** @brief A count of job identifiers that must be complete before this job starts. */
	u8 dependency_count;

	/** @brief An array of job identifiers that must be complete before this job starts. */
	u16 *dependency_ids;
} job_info;

typedef struct job_system_config {
	/**
	 * @param max_job_thread_count The maximum number of job threads to be spun up.
	 * Should be no more than the number of cores on the CPU, minus one to account for the main thread.
	 */
	u8 max_job_thread_count;
	/** @param type_masks A collection of type masks for each job thread. Must match max_job_thread_count. */
	u32 *type_masks;
} job_system_config;

/**
 * @brief Initializes the job system. Call once to retrieve job_system_memory_requirement, passing 0 to state. Then
 * call a second time with allocated state memory block.
 * @param job_system_memory_requirement A pointer to hold the memory required for the job system state in bytes.
 * @param state A block of memory to hold the state of the job system.
 * @param config A pointer to the configuration (job_system_config) of this system.
 * @returns True if the job system started up successfully; otherwise false.
 */
b8 job_system_initialize (u64 *job_system_memory_requirement, void *state, void *config);

/**
 * @brief Shuts the job system down.
 */
void job_system_shutdown (void *state);

/**
 * @brief Updates the job system. Should happen once an update cycle.
 */
b8 job_system_update (void *state, struct frame_data *p_frame_data);

/**
 * @brief Submits the provided job to be queued for execution.
 * @param info The description of the job to be executed.
 */
KAPI void job_system_submit (job_info info);

/**
 * @brief Creates a new job with default type (Generic) and priority (Normal).
 * @param entry_point A pointer to a function to be invoked when the job starts. Required.
 * @param on_success A pointer to a function to be invoked when the job completes successfully. Optional.
 * @param on_fail A pointer to a function to be invoked when the job fails. Optional.
 * @param param_data Data to be passed to the entry point upon execution.
 * @param param_data_size The data to be passed on to entry_point callback. Pass 0 if not used.
 * @param result_data_size The size of result data to be passed on to success callback. Pass 0 if not used.
 * @returns The newly created job information to be submitted for execution.
 */
KAPI job_info job_create (pfn_job_start entry_point, pfn_job_on_complete on_success, pfn_job_on_complete on_fail, void *param_data, u32 param_data_size, u32 result_data_size);

/**
 * @brief Creates a new job with default priority (Normal).
 * @param entry_point A pointer to a function to be invoked when the job starts. Required.
 * @param on_success A pointer to a function to be invoked when the job completes successfully. Optional.
 * @param on_fail A pointer to a function to be invoked when the job fails. Optional.
 * @param param_data Data to be passed to the entry point upon execution.
 * @param param_data_size The data to be passed on to entry_point callback. Pass 0 if not used.
 * @param result_data_size The size of result data to be passed on to success callback. Pass 0 if not used.
 * @param type The type of job. Used to determine which thread the job executes on.
 * @returns The newly created job information to be submitted for execution.
 */
KAPI job_info job_create_type (pfn_job_start entry_point, pfn_job_on_complete on_success, pfn_job_on_complete on_fail, void *param_data, u32 param_data_size, u32 result_data_size, job_type type);

/**
 * @brief Creates a new job with the provided priority.
 * @param entry_point A pointer to a function to be invoked when the job starts. Required.
 * @param on_success A pointer to a function to be invoked when the job completes successfully. Optional.
 * @param on_fail A pointer to a function to be invoked when the job fails. Optional.
 * @param param_data Data to be passed to the entry point upon execution.
 * @param param_data_size The data to be passed on to entry_point callback. Pass 0 if not used.
 * @param result_data_size The size of result data to be passed on to success callback. Pass 0 if not used.
 * @param type The type of job. Used to determine which thread the job executes on.
 * @param priority The priority of this job. Higher priority jobs obviously run sooner.
 * @returns The newly created job information to be submitted for execution.
 */
KAPI job_info job_create_priority (pfn_job_start entry_point, pfn_job_on_complete on_success, pfn_job_on_complete on_fail, void *param_data, u32 param_data_size, u32 result_data_size, job_type type, job_priority priority);

/**
 * @brief Creates a new job with the provided type, priority, and dependencies.
 * @param entry_point A pointer to a function to be invoked when the job starts. Required.
 * @param on_success A pointer to a function to be invoked when the job completes successfully. Optional.
 * @param on_fail A pointer to a function to be invoked when the job fails. Optional.
 * @param param_data Data to be passed to the entry point upon execution.
 * @param param_data_size The data to be passed on to entry_point callback. Pass 0 if not used.
 * @param result_data_size The size of result data to be passed on to success callback. Pass 0 if not used.
 * @param type The type of job. Used to determine which thread the job executes on.
 * @param priority The priority of this job. Higher priority jobs obviously run sooner.
 * @param dependency_count The number of job identifiers which must be complete before this job runs.
 * @param dependencies An array of job identifiers which must be complete before this job runs.
 * @returns The newly created job information to be submitted for execution.
 */
KAPI job_info job_create_with_dependencies (
	pfn_job_start entry_point,
	pfn_job_on_complete on_success,
	pfn_job_on_complete on_fail,
	void *param_data,
	u32 param_data_size,
	u32 result_data_size,
	job_type type,
	job_priority priority,
	u8 dependency_count,
	u16 *dependencies);

/**
 * @brief Returns whether or not the job with the given identifier has completed.
 */
KAPI b8 job_system_query_job_complete (u16 job_id);