#include "animone/util/osx.h"

#include <memory>
#include <string>

#include <libproc.h>
#include <sys/sysctl.h>

namespace animone::internal::osx::util {

typedef CFTypeRef (*LSASNCreateWithPidSpec)(CFAllocatorRef, pid_t);
typedef CFDictionaryRef (*LSCopyApplicationInformationSpec)(int, CFTypeRef, CFArrayRef);

/* retrieved dynamically from launchservices */
static LSCopyApplicationInformationSpec LSCopyApplicationInformation = nullptr;
static LSASNCreateWithPidSpec LSASNCreateWithPid = nullptr;

static CFStringRef kLSDisplayNameKey = nullptr;
static CFStringRef kLSPIDKey = nullptr;

/* retrieved from LaunchServicesSPI.h in WebKit */
static constexpr int kLSDefaultSessionID = -2;

static const CFStringRef kLaunchServicesBundleID = CFSTR("com.apple.LaunchServices");

static bool GetLaunchServicesPrivateSymbols() {
	CFBundleRef launch_services_bundle = CFBundleGetBundleWithIdentifier(kLaunchServicesBundleID);
	if (!launch_services_bundle)
		return false;

	LSCopyApplicationInformation = reinterpret_cast<LSCopyApplicationInformationSpec>(
	    CFBundleGetFunctionPointerForName(launch_services_bundle, CFSTR("_LSCopyApplicationInformation")));
	if (!LSCopyApplicationInformation)
		return false;

	LSASNCreateWithPid = reinterpret_cast<LSASNCreateWithPidSpec>(
	    CFBundleGetFunctionPointerForName(launch_services_bundle, CFSTR("_LSASNCreateWithPid")));
	if (!LSASNCreateWithPid)
		return false;

	CFStringRef* ptr_kLSDisplayNameKey = reinterpret_cast<CFStringRef*>(
	    CFBundleGetDataPointerForName(launch_services_bundle, CFSTR("_kLSDisplayNameKey")));
	if (!ptr_kLSDisplayNameKey)
		return false;
	kLSDisplayNameKey = *ptr_kLSDisplayNameKey;

	CFStringRef* ptr_kLSPIDKey =
	    reinterpret_cast<CFStringRef*>(CFBundleGetDataPointerForName(launch_services_bundle, CFSTR("_kLSPIDKey")));
	if (!ptr_kLSPIDKey)
		return false;
	kLSPIDKey = *ptr_kLSPIDKey;

	return true;
}

static bool LaunchServicesGetProcessName(pid_t pid, std::string& result) {
	if (!LSCopyApplicationInformation || !LSASNCreateWithPid || !kLSDisplayNameKey || !kLSPIDKey)
		if (!GetLaunchServicesPrivateSymbols())
			return false;

	/* what the hell is an `asn`? */
	CFPtr<CFTypeRef> asn = LSASNCreateWithPid(kCFAllocatorDefault, pid);
	if (!asn)
		return false;

	CFPtr<CFArrayRef> request_array = CFArrayCreate(NULL, (const void**)kLSDisplayNameKey, 1, NULL);
	if (!request_array)
		return false;

	CFPtr<CFDictionaryRef> dictionary =
	    LSCopyApplicationInformation(kLSDefaultSessionID, asn.get(), request_array.get());
	if (!dictionary)
		return false;

	{
		/* this doesn't need to be free'd */
		CFStringRef rstr;

		if (!CFDictionaryGetValueIfPresent(dictionary, kLSDisplayNameKey, (CFTypeRef*)&rstr) || !rstr)
			return false;

		if (!StringFromCFString(rstr, result))
			return false;
	}

	result.resize(result.find('\0'));

	return true;
}

bool StringFromCFString(CFStringRef string, std::string& result) {
	if (!string)
		return false;

	result.resize(CFStringGetMaximumSizeForEncoding(CFStringGetLength(string), kCFStringEncodingUTF8) + 1);
	if (!CFStringGetCString(string, &result.front(), result.length(), kCFStringEncodingUTF8))
		return false;

	return true;
}

static bool GetProcessArgs(pid_t pid, std::string& args) {
	/* sysctl shouldn't touch these, so we define them as const */
	int mib[3] = {CTL_KERN, KERN_PROCARGS2, static_cast<int>(pid)};
	const size_t mib_size = sizeof(mib) / sizeof(*mib);

	/* Get the initial size of the array
	 *
	 * NOTE: it IS possible for this value to change inbetween calls to sysctl().
	 * Unfortunately, I couldn't care less about handling this. :)
	 *
	 * is that really true, though? these should be constant values. but are
	 * argc and argv *really* constant?
	 */
	size_t size;
	{
		int ret = sysctl((int*)mib, mib_size, nullptr, &size, nullptr, 0);
		if (ret)
			return false;
	}

	/* Reserve the space for it in args */
	args.resize(size);

	/* Get the contents of argc and argv */
	{
		int ret = sysctl((int*)mib, mib_size, &args.front(), &size, NULL, 0);
		if (ret)
			return false;
	}

	/* Is the size big enough to hold at least argc? */
	if (size < sizeof(int))
		return false;

	args.resize(size);
	return true;
}

static bool GetProcessNameFromArgs(pid_t pid, std::string& result) {
	if (!GetProcessArgs(pid, result))
		return false;

	/* Get argc using memcpy */
	int argc = 0;
	memcpy(&argc, &result.front(), sizeof(argc));

	/* Do we even have argv[0]? */
	if (argc < 1)
		return false;

	/* Find the first null character */
	size_t null_pos = result.find('\0', sizeof(argc));
	if (null_pos == std::string::npos)
		return false;

	/* Find the last slash */
	size_t last_slash = result.rfind('/', null_pos);
	if (last_slash == std::string::npos)
		return false;

	/* Return our result */
	result = result.substr(last_slash + 1, null_pos - last_slash - 1);
	return true;
}

static bool GetProcessNameFromKernel(pid_t pid, std::string& result) {
	result.resize(2 * MAXCOMLEN);

	int size = proc_name(pid, &result.front(), result.length());
	if (!size)
		return false;

	result.resize(size);
	return true;
}

bool GetProcessName(pid_t pid, std::string& result) {
	if (LaunchServicesGetProcessName(pid, result))
		return true;

	/* Try parsing the arguments, this prevents the process name being
	 * cut off to 2*MAXCOMLEN (32 chars) */
	if (GetProcessNameFromArgs(pid, result))
		return true;

	/* Then attempt getting it from the kernel, which results in the
	 * process name being cut to 32 chars (worse, 16 chars if p_name is
	 * unavailable) */
	if (GetProcessNameFromKernel(pid, result))
		return true;

	return false;
}

} // namespace animone::internal::osx::util