#include "source_db.h"

#include "util.h"

#include <curl/curl.h>
#include <openssl/evp.h>
#include <openssl/sha.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

#define EXTRACT_TAR_SCRIPT "./scripts/extract_tar_contents.sh"

// libcrpyto context
EVP_MD_CTX *mdctx = NULL;
const EVP_MD *md = NULL;
void ensure_libcrypto();

// curl context
CURL *curl = NULL;
void ensure_libcurl();

// note: fixed location of source database for now
const char source_db_path[] = "./var/snag/sources";
char* get_source_path(const source_info_t* source) { return join_path(source_db_path, source->name); }

bool verify_source(source_info_t* source) {
	// verify source exists
	char* source_path = get_source_path(source);
	bool verified = access(source_path, F_OK) == 0;

	// todo(jqj): actually verify checksum
	free(source_path);
	return verified;
}

static size_t download_write_callback(char* ptr, size_t size, size_t nmemb, void* usrdata);
bool download_source(source_info_t* source) {

	char* source_path = get_source_path(source);
	print("Downloading %s\n", source->url);

	// initialize libcurl and libcrypto if they aren't already
	ensure_libcurl();
	ensure_libcrypto();

	// initialize sha256 hash
    EVP_DigestInit_ex(mdctx, md, NULL);

	// open file for writing
	FILE* download_file = fopen(source_path, "wb");
	if (download_file == NULL) die("failed open download file for writing (%s): %s", source_path, strerror(errno));

	// make curl request with url and output file
	// callback writes to the file and feeds the hash
	curl_easy_setopt(curl, CURLOPT_WRITEDATA, download_file);
	curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, download_write_callback);
	curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
	curl_easy_setopt(curl, CURLOPT_URL, source->url);
	CURLcode result = curl_easy_perform(curl);
	fclose(download_file);
    if(result != CURLE_OK) {
		// todo(jqj): handle better, maybe try again
		print("failed to download package with curl: %s", curl_easy_strerror(result));
		goto fail;
	}

	// get sha256 hash
    unsigned char hash[SHA256_DIGEST_LENGTH];
	unsigned int hash_len;
    EVP_DigestFinal_ex(mdctx, hash, &hash_len);

	// make hexadecimal string of sha256 hash
	char hash_hex[SHA256_DIGEST_LENGTH * 2 + 1];
	for(int i = 0; i < SHA256_DIGEST_LENGTH; i++) {
        sprintf(hash_hex + i*2,"%02x", hash[i]);
    }
	hash_hex[SHA256_DIGEST_LENGTH * 2] = '\0';

	// confirm that checksum matches
	assert(source->checksum != NULL); 
	if (strcmp(source->checksum, hash_hex) == 0) {
		print("checksum verified for download: %s\n", hash_hex);
		return true;
	} else {
		print("FAIL: bad checksum for download: %s\n", hash_hex);
		goto fail;
	}

fail:
    if (access(source_path, F_OK) == 0) remove(source_path);
	free(source_path);
	return false;
}

static size_t download_write_callback(char* ptr, size_t size, size_t nmemb, void* usrdata) {
	// write the curl data to the file in usr data
	size_t written = fwrite(ptr, size, nmemb, (FILE *)usrdata);

	// update the hash with the new data
    EVP_DigestUpdate(mdctx, ptr, written);

	return written;
}

bool unpack_source(const source_info_t* source, char* dest_path) {

	char* source_path = get_source_path(source);
	char* command = vastrcat(EXTRACT_TAR_SCRIPT, " ", source_path, " ", dest_path);

	// just run the unpack script. we can rewrite in c in the future
	int ret = system(command);
	if (ret == -1) {
		die("failed to execute unpack command '%s': %s", command, strerror(errno));
    } else if (!WIFEXITED(ret)) {
		die("failed to execute unpack command '%s' (didn't exit)", command);
	} else if (WEXITSTATUS(ret) != 0) {
		die("unpack command '%s' failed: exit status %d", command, WEXITSTATUS(ret));
	}

	free(command);
	free(source_path);

	return true;
}


void ensure_libcrypto() {
	if (mdctx == NULL) {
		mdctx = EVP_MD_CTX_new();
		md = EVP_sha256();
		/* come back to this if we have init and deinit */
		/* EVP_MD_CTX_free(mdctx); */
	}
}

void ensure_libcurl() {
	if (curl == NULL) {
		CURLcode result = curl_global_init(CURL_GLOBAL_ALL);
		if (result != CURLE_OK) die("failed to initialize curl: %s", curl_easy_strerror(result));
		curl = curl_easy_init(); // note(jqj): for now we reuse one easy curl object
		if (curl == NULL) die("failed to initialize easy curl");
		/* come back to this if we have init and deinit */
		/* curl_easy_cleanup(curl); */
		/* curl_global_cleanup(); */
	}
}