//
// Cforall Version 1.0.0 Copyright (C) 2021 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// topology.cfa -- read the data structure
//
// Author           : Thierry Delisle
// Created On       : Thu Jun 10 16:13:07 2021
// Last Modified By :
// Last Modified On :
// Update Count     :
//

#include "device/cpu.hfa"

#include <math.hfa>
#include <stdlib.hfa>

#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

extern "C" {
	#include <dirent.h>
	#include <sys/types.h>
	#include <sys/stat.h>
	#include <fcntl.h>
}

// search a string for character 'character' but looking atmost at len
// chars
static const char * strnchr(const char * str, int character, size_t len) {
	return (const char *)memchr(str, character, strnlen(str, len));
}

// Check if have string matches the want string
// ignoring any characters that are longer than the want string
static bool strmatch(const char * want, char * have) {
	size_t w = strlen(want);
	return strncmp(want, have, w) == 0;
}

typedef const char * idx_range_t;

// read the value of a string and evaluate it
// get the end pointer and make sure it is all evaluated
static unsigned read_value(idx_range_t map, size_t len, const char ** end) {
	unsigned long val = strtoul(map, (char**)end, 10);
	/* paranoid */ __attribute__((unused)) size_t read = (*end - map);
	/* paranoid */ verifyf(read <= len, "String '%s' passed with inconsistent length %zu", map, len);
	/* paranoid */ verifyf(read == len, "String %.*s not entirely a number, %zu chars left", (int)len, map, len - read);
	return val;
}

// Evaluate the width of a comma seperated list of idx
// for example 'A-B,C-D,E,F' has a width of '(B-A) + (D-C) + 1 + 1'
// Also has an (non-optional) end ptr like strtoul and friends
//
// FIXME : the current implementation only supports 1 comma
static unsigned read_width(idx_range_t map, size_t len, const char ** end) {
	// Do we have a comma
	const char * comma = strnchr(map, ',', len);
	if(comma != 0p) {
		// We do! recurse and sum the widths
		const char * _;
		size_t split = comma - map;
		unsigned lhs = read_width(map, split, &_);
		unsigned rhs = read_width(comma + 1, len - split - 1, end);
		return lhs + rhs;
	}

	// No commas, check for a range
	const char * dash = strnchr(map, '-', len);
	if(dash != 0p) {
		const char * _;
		size_t split = dash - map;
		unsigned lhs = read_value(map, split, &_);
		unsigned rhs = read_value(dash + 1, len - split - 1, end);
		return rhs - lhs + 1;
	}

	// No range, no comma, just a single value
	// It's width is 1 and we can consume everything
	/* paranoid */ verifyf( ({strtoul(map, (char**)end, 10); *end == (map + len); }), "Value in range '%.*s' not a number", (int)len, map);
	*end = map + len;
	return 1;
}

// go through a directory calling fn on each file
static int iterate_dir( const char * path, void (*fn)(struct dirent * ent) ) {
	// open the directory
	DIR *dir = opendir(path);
	if(dir == 0p) { return ENOTDIR; }

	// call fn for each
	struct dirent * ent;
	while ((ent = readdir(dir)) != 0p) {
		fn( ent );
	}

	// no longer need this
	closedir(dir);
	return 0;
}

// count the number of directories with the specified prefix
// the directories counted have the form '[prefix]N' where prefix is the parameter
// and N is an base 10 integer.
static int count_prefix_dirs(const char * path, const char * prefix) {
	// read the directory and find the cpu count
	// and make sure everything is as expected
	int max = -1;
	int count = 0;
	void lambda(struct dirent * ent) {
		// were are looking for prefixX, where X is a number
		// check that it starts with 'cpu
		char * s = strstr(ent->d_name, prefix);
		if(s == 0p) { return; }
		if(s != ent->d_name) { return; }

		// check that the next part is a number
		s += strlen(prefix);
		char * end;
		long int val = strtol(s, &end, 10);
		if(*end != '\0' || val < 0) { return; }

		// check that it's a directory
		if(ent->d_type != DT_DIR) { return; }

		// it's a match!
		max = max(val, max);
		count++;
	}
	iterate_dir(path, lambda);

	/* paranoid */ verifyf(count == max + 1, "Inconsistent %s count, counted %d, but max %s was %d", prefix, count, prefix, (int)max);

	return count;
}

// Count number of cpus in the system
static int count_cpus(void) {
	const char * fpath = "/sys/devices/system/cpu/present";
	int fd = open(fpath, 0, O_RDONLY);
	/* paranoid */ verifyf(fd >= 0, "Could not open file %s", fpath);

	char buff[128];
	ssize_t r = read(fd, buff, 128);
	/* paranoid */ verifyf(r > 0, "Could not read file %s", fpath);
	/* paranoid */ verify( buff[r-1] == '\n' );
	buff[r-1] = '\0';

	/* paranoid */ __attribute__((unused)) int ret =
	close(fd);
	/* paranoid */ verifyf(ret == 0, "Could not close file %s", fpath);

	const char * _;
	int cnt = read_width(buff, r - 1, &_);
	/* paranoid */ verify(cnt == count_prefix_dirs("/sys/devices/system/cpu", "cpu"));
	return cnt;
}

// Count number of cache *indexes* in the system
// cache indexes are distinct from cache level as Data or Instruction cache
// can share a level but not an index
// PITFALL: assumes all cpus have the same indexes as cpu0
static int count_cache_indexes(void) {
	return count_prefix_dirs("/sys/devices/system/cpu/cpu0/cache", "index");
}


// read information about a spcficic cache index/cpu file into the output buffer
static size_t read_cpuidxinfo_into(unsigned cpu, unsigned idx, const char * file, char * out, size_t out_len) {
	// Pick the file we want and read it
	char buf[128];
	/* paranoid */ __attribute__((unused)) int len =
	snprintf(buf, 128, "/sys/devices/system/cpu/cpu%u/cache/index%u/%s", cpu, idx, file);
	/* paranoid */ verifyf(len > 0, "Could not generate '%s' filename for cpu %u, index %u", file, cpu, idx);

	int fd = open(buf, 0, O_RDONLY);
	/* paranoid */ verifyf(fd > 0, "Could not open file '%s'", buf);

	ssize_t r = read(fd, out, out_len);
	/* paranoid */ verifyf(r > 0, "Could not read file '%s'", buf);

	/* paranoid */ __attribute__((unused)) int ret =
	close(fd);
	/* paranoid */ verifyf(ret == 0, "Could not close file '%s'", buf);
	return r;
}

// Iterate over the cache indexes of a given cpu
typedef void (*handle_func_t)(unsigned idx, unsigned char level, idx_range_t range, size_t len);
static void foreach_cacheidx(unsigned cpu, unsigned idxs, handle_func_t handle) {
	for(i; idxs) {
		unsigned idx = idxs - 1 - i;
		char buf[32];

		// Type says what kind of cache this is,
		// Options are: Unified, Data, Instruction
		read_cpuidxinfo_into(cpu, idx, "type", buf, 32);
		if((!strmatch("Unified", buf)) && (!strmatch("Data", buf))) {
			// We don't care about instruction caches
			continue;
		}

		// Level is the cache level: higher means bigger and slower
		read_cpuidxinfo_into(cpu, idx, "level", buf, 32);
		char * end;
		unsigned long level = strtoul(buf, &end, 10);
		/* paranoid */ verifyf(level <= 250, "Cpu %u has more than 250 levels of cache, this is not supported", cpu);

		// shared_cpu_list is a range of cpus that share this particular cache
		size_t n = read_cpuidxinfo_into(cpu, idx, "shared_cpu_list", buf, 32);
		/* paranoid */ verify( buf[n-1] == '\n' );
		buf[n-1] = '\0';

		// Simply call the functor
		handle(idx, level, buf, n - 1);
	}
}


struct raw_cache_instance {
	idx_range_t range;
	unsigned width;
	unsigned char level;
	// FIXME add at least size and type
};

static void  ?{}(raw_cache_instance & this) { this.range = 0p;}
static void ^?{}(raw_cache_instance & this) { free(this.range);}

raw_cache_instance ** build_raw_cache_table(unsigned cpus, unsigned idxs, unsigned cache_levels)
{
	raw_cache_instance ** raw = alloc(cpus);
	for(i; cpus) {
		raw[i] = alloc(cache_levels);
		void addcache(unsigned fidx, unsigned char level, idx_range_t range, size_t len) {
			/* paranoid */ verifyf(level <= cache_levels, "Unexpected cache level %d on cpu %u index %u", (int)level, i, fidx);

			unsigned idx = cache_levels - level;
			raw_cache_instance & r = raw[i][idx];
			r.range = strndup(range, len);
			r.level = level;
			const char * end;
			r.width = read_width(range, len, &end);
		}
		foreach_cacheidx(i, idxs, addcache);
	}

	return raw;
}

// returns an allocate list of all the different distinct last level caches
static [*idx_range_t, size_t cnt] distinct_llcs(unsigned cpus, unsigned llc_idx, raw_cache_instance ** raw) {
	// Allocate at least one element
	idx_range_t * ranges = alloc();
	size_t range_cnt = 1;

	// Initialize with element 0
	*ranges = raw[0][llc_idx].range;

	// Go over all other cpus
	CPU_LOOP: for(i; 1~cpus) {
		// Check if the range is already there
		idx_range_t candidate = raw[i][llc_idx].range;
		for(j; range_cnt) {
			idx_range_t exist = ranges[j];
			// If the range is already there just jump to the next cpu
			if(0 == strcmp(candidate, exist)) continue CPU_LOOP;
		}

		// The range wasn't there, added to the list
		ranges = alloc(range_cnt + 1, ranges`realloc);
		ranges[range_cnt] = candidate;
		range_cnt++;
	}

	// return what we have
	return [ranges, range_cnt];
}

struct cpu_pairing_t {
	unsigned cpu;
	unsigned llc_id;
};

int ?<?( cpu_pairing_t lhs, cpu_pairing_t rhs ) {
	return lhs.llc_id < rhs.llc_id;
}

static [[]cpu_pairing_t] get_cpu_pairings(unsigned cpus, raw_cache_instance ** raw, idx_range_t * maps, size_t map_cnt) {
	cpu_pairing_t * pairings = alloc(cpus);

	CPU_LOOP: for(i; cpus) {
		pairings[i].cpu = i;
		idx_range_t want = raw[i][0].range;
		MAP_LOOP: for(j; map_cnt) {
			if(0 != strcmp(want, maps[j])) continue MAP_LOOP;

			pairings[i].llc_id = j;
			continue CPU_LOOP;
		}

		/* paranoid */ verifyf( false, "Cpu %u map doesn't match", i );
	}

	return pairings;
}

extern "C" {
	void __cfaabi_device_startup( void ) {
		int cpus = count_cpus();
		int idxs = count_cache_indexes();

		// Count actual cache levels
		unsigned cache_levels = 0;
		unsigned llc = 0;
		{
			unsigned char prev = -1u;
			void first(unsigned idx, unsigned char level, const char * map, size_t len) {
				/* paranoid */ verifyf(level < prev, "Index %u of cpu 0 has cache levels out of order: %u then %u", idx, (unsigned)prev, (unsigned)level);
				llc = max(llc, level);
				prev = level;
				cache_levels++;
			}
			foreach_cacheidx(0, idxs, first);
		}

		// Read in raw data
		raw_cache_instance ** raw = build_raw_cache_table(cpus, idxs, cache_levels);

		// Find number of distinct cache instances
		idx_range_t * maps;
		size_t map_cnt;
		[maps, map_cnt] =  distinct_llcs(cpus, cache_levels - llc, raw);

		#if defined(__CFA_WITH_VERIFY__)
		{
			unsigned width = 0;
			for(i; map_cnt) {
				const char * _;
				width += read_width(maps[i], strlen(maps[i]), &_);
			}
			verify(width == cpus);
		}
		#endif

		// Get mappings from cpu to cache instance
		cpu_pairing_t * pairings = get_cpu_pairings(cpus, raw, maps, map_cnt);

		// Sort by cache instance
		qsort(pairings, cpus);

		unsigned llc_width = raw[0][cache_levels - llc].width;

		// From the mappins build the actual cpu map we want
		struct cpu_map_entry_t * entries = alloc(cpus);
		for(i; cpus) { entries[i].count = 0; }
		for(i; cpus) {
			unsigned c = pairings[i].cpu;
			entries[c].start = pairings[i].llc_id * llc_width;
			entries[c].count = llc_width;
		}

		// get rid of the temporary data
		free(maps);
		free(pairings);

		for(i; cpus) {
			for(j; cache_levels) {
				^(raw[i][j]){};
			}
			free(raw[i]);
		}
		free(raw);

		cpu_info.llc_map = entries;
		cpu_info.hthrd_count = cpus;
	}

	void __cfaabi_device_shutdown( void ) {
		free(cpu_info.llc_map);
	}
}