#include "parallel.h"

#include <mpi.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <malloc.h>
#include <stdlib.h>

#define DEBUG(msg, ...)
#define INFO(msg, ...) fprintf(stderr, "[%003d%10.3f] " msg, mpi_rank(0), runtime(), ##__VA_ARGS__)
//#define DEBUG(msg, ...) fprintf(stderr, "[   %10.3f] " msg, runtime(), ##__VA_ARGS__)
//#define DEBUG_MPI(msg, node, ...) fprintf(stderr, "[%003d%10.3f] " msg, node, runtime(), ##__VA_ARGS__)
#define DONE(x) *((int*)(x))

enum message_tag {
	PARALLEL_ORDER,
	PARALLEL_RESULT,
	PARALLEL_SHUTDOWN,
	PARALLEL_GLOBAL_DATA
};

struct timespec starttime;

int mpi_rank(int activate_mpi)
{
	static int active = 0;
	if(activate_mpi)
		active = 1;

	if(!active)
		return 0;
	else {
		int rank;
		MPI_Comm_rank(MPI_COMM_WORLD, &rank);
		return rank;
	}
}

void start_timer()
{
	clock_gettime(CLOCK_MONOTONIC, &starttime);
}

double runtime()
{
	struct timespec curtime;
	double diff;
	clock_gettime(CLOCK_MONOTONIC, &curtime);
	return (curtime.tv_sec - starttime.tv_sec) + (curtime.tv_nsec - starttime.tv_nsec) / 1e9;
}

parallel_context *parallel_init()
{
	parallel_context *ctx = malloc(sizeof(parallel_context));

	if(!getenv("OMPI_COMM_WORLD_SIZE")) {
		ctx->mpi_mode = 0;
		DEBUG("Running standalone.\n");
		return ctx;
	}

	ctx->mpi_mode = 1;
	int result = MPI_Init(NULL, NULL);
	MPI_Comm_size(MPI_COMM_WORLD, &ctx->size);
	MPI_Comm_rank(MPI_COMM_WORLD, &ctx->rank);
	MPI_Get_processor_name(ctx->processor_name, &ctx->processor_name_len);

	mpi_rank(1); // display the rank in debug output from now on

	if(ctx->rank == 0)
		DEBUG("Running in mpi mode, %d nodes.\n", ctx->size);

	return ctx;
}

void parallel_destroy(parallel_context* ctx)
{
	if(ctx->mpi_mode) {
		MPI_Type_free(&ctx->order_datatype);
		MPI_Type_free(&ctx->result_datatype);
		MPI_Finalize();
	}

	free(ctx);
}

void parallel_set_datasize_and_callbacks(parallel_context *ctx, parallel_callback_init init, parallel_callback_job job, parallel_callback_destroy destroy, int global_data_size, int node_data_size, int input_size, int output_size)
{
	ctx->init = init;
	ctx->destroy = destroy;
	ctx->job = job;
	ctx->global_data_size = global_data_size;
	ctx->node_data_size = node_data_size;
	ctx->input_size = input_size;
	ctx->output_size = output_size;

	if(ctx->mpi_mode) {
		// create a datatype for job orders, consisting of an integer (the job id) and a user-defined section
		int order_blocklengths[2] = {1, input_size};
		MPI_Aint order_displacements[2] = {0, sizeof(int)};
		MPI_Datatype order_types[2] = {MPI_INT, MPI_BYTE};
		MPI_Type_create_struct(2, order_blocklengths, order_displacements, order_types, &ctx->order_datatype);
		MPI_Type_commit(&ctx->order_datatype);

		int result_blocklengths[2] = {1, output_size};
		MPI_Aint result_displacements[2] = {0, sizeof(int)};
		MPI_Datatype result_types[2] = {MPI_INT, MPI_BYTE};
		MPI_Type_create_struct(2, result_blocklengths, result_displacements, result_types, &ctx->result_datatype);
		MPI_Type_commit(&ctx->result_datatype);
	}
}

int parallel_work(parallel_context *ctx)
{
	// do nothing in non-mpi mode
	if(ctx->mpi_mode == 0)
		return 0;

	MPI_Status status;
	void *global_data = malloc(ctx->global_data_size);
	void *node_data = malloc(ctx->node_data_size);
	void *input_and_job_nr = malloc(ctx->input_size + sizeof(int));
	void *input = input_and_job_nr + sizeof(int);
	int *job_nr = (int *)input_and_job_nr;
	void *output_and_job_nr = malloc(ctx->output_size + sizeof(int));
	void *output = output_and_job_nr + sizeof(int);
	int *output_job_nr = (int *)output_and_job_nr;
	double jobtime;

	// wait for global data
	MPI_Bcast(global_data, ctx->global_data_size, MPI_BYTE, 0, MPI_COMM_WORLD);

	DEBUG("Global data received\n");

	// initialize node_data (and do once-per-node computation)
	ctx->init(global_data, node_data);

	DEBUG("Initialization completed\n");

	while(1) {
		MPI_Probe(0, MPI_ANY_TAG, MPI_COMM_WORLD,
		          &status);

//		DEBUG("Message received: source = %d, tag = %d\n", status.MPI_SOURCE, status.MPI_TAG);

		if(status.MPI_TAG == PARALLEL_SHUTDOWN) {
			DEBUG("Shutting down\n");
			break;
		} else if(status.MPI_TAG == PARALLEL_ORDER) {
			MPI_Recv(input_and_job_nr,
			         1, ctx->order_datatype,
			         0, PARALLEL_ORDER, MPI_COMM_WORLD,
			         &status);

			DEBUG("Working on job %d\n", *job_nr);

			jobtime = -MPI_Wtime();

			// do the actual work
			ctx->job(global_data, node_data, input, output);

			jobtime += MPI_Wtime();

			DEBUG("Finished job %d in %f seconds\n", *job_nr, jobtime);

			*output_job_nr = *job_nr;
			MPI_Send(output_and_job_nr,
			         1, ctx->result_datatype,
			         0, PARALLEL_RESULT, MPI_COMM_WORLD);
		}
	}

	ctx->destroy(global_data, node_data);

	free(global_data);
	free(node_data);
	free(input_and_job_nr);
	free(output_and_job_nr);

	return 0;
}

int parallel_run(parallel_context *ctx, const void *global_data, const void *input_array, void *output_array, unsigned int njobs, const char *_restart_filename)
{
	// in non-mpi-mode, just run init1, init2, forall(jobs) job
	if(ctx->mpi_mode == 0) {
		int result;
		void *node_data = malloc(ctx->node_data_size);
		result = ctx->init(global_data, node_data);
		if(result != 0)
			goto cleanup_standalone;

		for(int i = 0; i < njobs; i++) {
			result = ctx->job(
				global_data,
				node_data,
				input_array + ctx->input_size*i,
				output_array + ctx->output_size*i);
			if(result != 0)
				goto cleanup_standalone;
		}

	cleanup_standalone:
		ctx->destroy(global_data, node_data);
		return result;
	} else {
		// if no restart file was specified, pick a filename
		char *restart_filename;
		char buffer[128];
		int restartf;
		if(_restart_filename == NULL) {
			time_t t = time(NULL);
			struct tm *loctm = localtime(&t);
			strftime(buffer, sizeof(buffer), "restart/restart_%y%m%d_%H%M%S", loctm);
			restart_filename = buffer;
		} else {
			restart_filename = (char *)_restart_filename;
		}

		// open restart file if it exists, otherwise create it
		int continuing = 1;
		restartf = open(restart_filename, O_RDWR);
		if(restartf == -1 && errno == ENOENT) {
			restartf = open(restart_filename, O_RDWR | O_CREAT, 0666);
			continuing = 0;
		}
		if(restartf == -1) {
			DEBUG("Error opening restart file: %s\n", strerror(errno));
			exit(1);
		}

		// map restart file
		int itemsize = (ctx->output_size + sizeof(int)); // for every job, store output, and completed flag
		ftruncate(restartf, njobs*itemsize);
		void *alljobs = mmap(0, njobs*itemsize, PROT_READ | PROT_WRITE, MAP_SHARED, restartf, 0);
		if(alljobs == MAP_FAILED) {
			DEBUG("Error mapping restart file: %s\n", strerror(errno));
			exit(1);
		}

		// count completed jobs, or initialize jobs
		int completed = 0;
		if(continuing) {
			for(int i = 0; i < njobs; i++)
				if(DONE(alljobs + i*itemsize))
					completed++;
		} else {
			for(int i = 0; i < njobs; i++) {
				DONE(alljobs + i*itemsize) = 0;
				memcpy(alljobs + i*itemsize + sizeof(int), input_array + i*ctx->input_size, ctx->input_size); // copy input data
			}
		}

		fsync(restartf);

		if(continuing) {
			INFO("Continuing from restart file, %d/%d jobs completed, %d nodes\n", completed, njobs, ctx->size);
		} else {
			INFO("Starting from scratch, %d jobs, %d nodes\n", njobs, ctx->size);
		}

		if(completed >= njobs)
			goto cleanup_mpi;

		/* Send global data */
		MPI_Bcast((void*)global_data, ctx->global_data_size, MPI_BYTE, 0, MPI_COMM_WORLD);

		DEBUG("Global data sent\n");

		void *input_message_buffer = malloc(ctx->input_size + sizeof(int));
		void *output_message_buffer = malloc(ctx->output_size + sizeof(int));

		// find next unfinished job
		int current = 0;
		while(current < njobs && DONE(alljobs + current*itemsize))
			current++;

		// assign initial jobs, 2 for each worker thread
		for(int i = 0; i < 2*(ctx->size-1); i++) {
			if(current >= njobs) // all jobs are assigned
				break;

			// send job id and input data
			// send to all nodes except ourself (node 0)
			*((int*)input_message_buffer) = current;
			memcpy(input_message_buffer + sizeof(int), input_array + current*ctx->input_size, ctx->input_size);
			MPI_Send(input_message_buffer, 1, ctx->order_datatype,
			         i%(ctx->size-1)+1, PARALLEL_ORDER, MPI_COMM_WORLD);

			DEBUG("Job %d sent to node %d\n", current, i%(ctx->size-1)+1);
			current++;
		}

		MPI_Status status;
		int active_worker_nodes = ctx->size - 1;
		while(1) {
			MPI_Probe(MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
			if(status.MPI_TAG == PARALLEL_RESULT) {
				MPI_Recv(output_message_buffer, 1, ctx->result_datatype,
				         MPI_ANY_SOURCE, PARALLEL_RESULT, MPI_COMM_WORLD, &status);

				int id = *((int*)output_message_buffer);
				memcpy(alljobs + id*itemsize + sizeof(int), output_message_buffer + sizeof(int), ctx->output_size);
				DONE(alljobs + id*itemsize) = 1;
				completed++;

				// todo: deal with unresponsive nodes
				// strategy: when no jobs left, go through unfinished list again, incrementing oversubscribe counter
				// if oversubscribe counter is at limit, shut node down instead
				//

				if(current >= njobs) { // all jobs are assigned, shut down node
					INFO("job %d completed by node %d, shut down\n", id, status.MPI_SOURCE);
					MPI_Send(NULL, 0, MPI_BYTE, status.MPI_SOURCE, PARALLEL_SHUTDOWN, MPI_COMM_WORLD);
					active_worker_nodes--;
					if(!active_worker_nodes)
						break;
				} else {
					INFO("job %d completed by node %d, continues with %d\n", id, status.MPI_SOURCE, current);
					*((int*)input_message_buffer) = current;
					memcpy(input_message_buffer + sizeof(int), input_array + current*ctx->input_size, ctx->input_size);
					MPI_Send(input_message_buffer, 1, ctx->order_datatype,
					         status.MPI_SOURCE, PARALLEL_ORDER, MPI_COMM_WORLD);
					current++;
				}
			}
		}

		for(int i = 0; i < njobs; i++) {
			memcpy(output_array + i*ctx->output_size, alljobs + i*itemsize + sizeof(int), ctx->output_size);
		}

		free(input_message_buffer);
		free(output_message_buffer);

	cleanup_mpi:
		munmap(alljobs, njobs*itemsize);
		close(restartf);
	}

	return 0;
}