#define _POSIX_C_SOURCE 200809L

#include <fx/collections/array.h>
#include <fx/diagnostics/process.h>
#include <fx/global.h>
#include <fx/io/path.h>
#include <fx/io/pipe.h>
#include <fx/io/stream.h>
#include <fx/iterator.h>
#include <fx/macros.h>
#include <fx/string.h>
#include <signal.h>
#include <sys/wait.h>
#include <unistd.h>

static fx_process *self = NULL;

extern const char **environ;

FX_API fx_type_id fx_process_iterator_get_type();

FX_DECLARE_TYPE(fx_process_iterator);

FX_TYPE_CLASS_DECLARATION_BEGIN(fx_process_iterator)
FX_TYPE_CLASS_DECLARATION_END(fx_process_iterator)

struct fx_process_p {
	fx_string *proc_exec_path;
	fx_array *proc_args;
	bool proc_redirect_stdin, proc_redirect_stdout, proc_redirect_stderr;
	fx_stream *proc_stdin, *proc_stdout, *proc_stderr;
	pid_t proc_id;
	fx_hashtable *proc_environment;
};

struct fx_process_iterator_p {
};

/*** PRIVATE FUNCTIONS ********************************************************/

static bool exec_name_is_path(const char *s)
{
	fx_wchar c;
	while (*s) {
		c = fx_wchar_utf8_codepoint_decode(s);
		if (c == FX_WCHAR_INVALID) {
			break;
		}

		if (c == '/') {
			return true;
		}

		s += fx_wchar_utf8_codepoint_stride(s);
	}

	return false;
}

const fx_string *get_path(void)
{
	const char *path_env = NULL;
	fx_process *self = fx_process_get_self();
	if (!self) {
		goto fallback;
	}

	const fx_hashtable *env = fx_process_get_environment(self);
	if (!env) {
		goto fallback;
	}

	const fx_value *path_v = fx_hashtable_get(env, &FX_CSTR("PATH"));
	if (!path_v) {
		goto fallback;
	}

	fx_string *result = NULL;
	fx_value_get_object(path_v, &result);
	return result;

fallback:
	path_env = getenv("PATH");
	if (!path_env) {
		return NULL;
	}

	return fx_string_create_from_cstr(path_env);
}

static fx_status find_executable(fx_string *exec_path)
{
	const char *exec_path_cstr = fx_string_get_cstr(exec_path);
	const fx_string *path_env = get_path();
	if (!path_env) {
		return FX_ERR_NO_ENTRY;
	}

	const char *delim[] = {":"};
	size_t nr_delim = sizeof delim / sizeof delim[0];
	fx_path *path = NULL;
	fx_iterator *it = fx_string_tokenise(
		path_env,
		delim,
		nr_delim,
		FX_STRING_TOK_F_NORMAL);
	fx_status status = FX_ERR_NO_ENTRY;

	fx_foreach(tok, it)
	{
		path = fx_path_join_list(2, tok, &FX_VALUE_OBJECT(exec_path));
		if (fx_path_is_file(path)) {
			fx_string_clear(exec_path);
			fx_string_append_cstr(
				exec_path,
				fx_path_get_cstr(path));
			status = FX_SUCCESS;
			break;
		}
	}

	fx_iterator_unref(it);
	fx_path_unref(path);

	return status;
}

static fx_status process_start(struct fx_process_p *proc)
{
	fx_iostream *in_r = NULL, *in_w = NULL;
	fx_iostream *out_r = NULL, *out_w = NULL;
	fx_iostream *err_r = NULL, *err_w = NULL;
	fx_status status = FX_SUCCESS;
	bool name_is_path
		= exec_name_is_path(fx_string_get_cstr(proc->proc_exec_path));

	if (!name_is_path) {
		status = find_executable(proc->proc_exec_path);
	}

	if (!FX_OK(status)) {
		return status;
	}

	if (proc->proc_redirect_stdin) {
		status = fx_pipe_create(&in_r, &in_w);
		if (!FX_OK(status)) {
			goto cleanup;
		}
	}

	if (proc->proc_redirect_stdout) {
		status = fx_pipe_create(&out_r, &out_w);
		if (!FX_OK(status)) {
			goto cleanup;
		}
	}

	if (proc->proc_redirect_stderr) {
		status = fx_pipe_create(&err_r, &err_w);
		if (!FX_OK(status)) {
			goto cleanup;
		}
	}

	pid_t pid = fork();

	if (pid < 0) {
		status = FX_ERR_INVALID_ARGUMENT;
		goto cleanup;
	}

	if (pid > 0) {
		proc->proc_id = pid;
		proc->proc_stdin = fx_iostream_ref(in_w);
		proc->proc_stdout = fx_iostream_ref(out_r);
		proc->proc_stderr = fx_iostream_ref(err_r);
		status = FX_SUCCESS;
		goto cleanup;
	}

	int fd = -1;
	if (proc->proc_redirect_stdin) {
		fx_iostream_unref(in_w);
		fd = fx_iostream_steal_os_handle(in_r);
		int err = dup2(fd, 0);
		close(fd);
	}

	if (proc->proc_redirect_stdout) {
		fx_iostream_unref(out_r);
		fd = fx_iostream_steal_os_handle(out_w);
		dup2(fd, 1);
		close(fd);
	}

	if (proc->proc_redirect_stderr) {
		fx_iostream_unref(err_r);
		fd = fx_iostream_steal_os_handle(err_w);
		dup2(fd, 2);
		close(fd);
	}

	const char **argv = NULL;
	const char **envp = NULL;
	const char *default_argv[] = {
		fx_string_get_cstr(proc->proc_exec_path),
		NULL,
	};

	size_t argc = 0;
	size_t envc = 0;

	if (proc->proc_args) {
		argc = fx_array_get_size(proc->proc_args);
	}

	if (proc->proc_environment) {
		envc = fx_hashtable_get_count(proc->proc_environment);
	}

	if (argc) {
		argv = calloc(argc + 1, sizeof(char *));

		for (size_t i = 0; i < argc; i++) {
			const fx_value *arg_value
				= fx_array_get_ref(proc->proc_args, i);
			fx_value_get_cstr(arg_value, &argv[i]);
		}
	} else {
		argv = default_argv;
	}

	if (envc) {
		envp = calloc(envc + 1, sizeof(char *));
		size_t i = 0;
		fx_stringstream *tmp = fx_stringstream_create();
		const fx_iterator *it
			= fx_iterator_begin(proc->proc_environment);
		fx_foreach(v, it)
		{
			fx_hashtable_item *item = NULL;
			fx_value_get_object(v, &item);
			const fx_value *name_v
				= fx_hashtable_item_get_key(item);
			const fx_value *value_v
				= fx_hashtable_item_get_value(item);

			fx_value_to_string(name_v, tmp, NULL);
			fx_stream_write_char(tmp, '=');
			fx_value_to_string(value_v, tmp, NULL);
			envp[i++] = fx_stringstream_steal(tmp);
		}

		fx_iterator_unref(it);
		fx_string_unref(tmp);
	}

	execve(fx_string_get_cstr(proc->proc_exec_path),
	       (char *const *)argv,
	       (char *const *)envp);
	exit(127);

cleanup:
	fx_iostream_unref(in_r);
	fx_iostream_unref(in_w);
	fx_iostream_unref(out_r);
	fx_iostream_unref(out_w);
	fx_iostream_unref(err_r);
	fx_iostream_unref(err_w);
	return status;
}

static fx_status process_wait(struct fx_process_p *proc, int *out_result)
{
	if (proc->proc_id == 0) {
		return FX_ERR_BAD_STATE;
	}

	int status = 0;

	do {
		int err = waitpid(proc->proc_id, &status, WUNTRACED);
		if (err != 0) {
			return FX_ERR_BAD_STATE;
		}
	} while (!WIFEXITED(status));

	proc->proc_id = 0;
	*out_result = WEXITSTATUS(status);
	return FX_ERR_NOT_SUPPORTED;
}

static fx_status process_kill(struct fx_process_p *proc)
{
	if (proc->proc_id == 0) {
		return FX_ERR_BAD_STATE;
	}

	int err = kill(proc->proc_id, SIGTERM);
	if (err != 0) {
		return FX_ERR_BAD_STATE;
	}

	return FX_SUCCESS;
}

static const fx_hashtable *process_get_environment(
	const struct fx_process_p *proc)
{
	return proc->proc_environment;
}

static fx_stream *process_get_stdin(struct fx_process_p *proc)
{
	return proc->proc_stdin;
}

static fx_stream *process_get_stdout(struct fx_process_p *proc)
{
	return proc->proc_stdout;
}

static fx_stream *process_get_stderr(struct fx_process_p *proc)
{
	return proc->proc_stderr;
}

static void process_close_stdin(struct fx_process_p *proc)
{
	fx_iostream_unref(proc->proc_stdin);
	proc->proc_stdin = NULL;
}

static void process_close_stdout(struct fx_process_p *proc)
{
	fx_iostream_unref(proc->proc_stdout);
	proc->proc_stdout = NULL;
}

static void process_close_stderr(struct fx_process_p *proc)
{
	fx_iostream_unref(proc->proc_stderr);
	proc->proc_stderr = NULL;
}

/*** PUBLIC FUNCTIONS *********************************************************/

fx_process *fx_process_create(const fx_process_start_info *info)
{
	fx_process *out = fx_object_create(FX_DIAGNOSTICS_TYPE_PROCESS);
	if (!out) {
		return NULL;
	}

	struct fx_process_p *proc
		= fx_object_get_private(out, FX_DIAGNOSTICS_TYPE_PROCESS);

	proc->proc_exec_path = fx_string_create_from_cstr(info->proc_file_name);
	if (!proc->proc_exec_path) {
		fx_process_unref(out);
		return NULL;
	}

	proc->proc_args = fx_array_ref((fx_array *)info->proc_args);

	proc->proc_environment
		= fx_hashtable_ref((fx_hashtable *)info->proc_environment);
	proc->proc_redirect_stdin = info->proc_redirect_stdin;
	proc->proc_redirect_stdout = info->proc_redirect_stdout;
	proc->proc_redirect_stderr = info->proc_redirect_stderr;

	return out;
}

fx_process *fx_process_get_self(void)
{
	if (self) {
		return self;
	}

	self = fx_object_create(FX_DIAGNOSTICS_TYPE_PROCESS);
	if (!self) {
		return NULL;
	}

	struct fx_process_p *proc
		= fx_object_get_private(self, FX_DIAGNOSTICS_TYPE_PROCESS);

	proc->proc_id = getpid();
	fx_hashtable *env = fx_hashtable_create();

	for (size_t i = 0; environ[i]; i++) {
		char *envstr = fx_strdup(environ[i]);

		const char *name = envstr;
		char *sep = strchr(name, '=');
		const char *value = NULL;
		if (sep) {
			*sep = '\0';
			value = sep + 1;
		}

		fx_string *name_str = fx_string_create_from_cstr(name);
		fx_string *value_str = fx_string_create();
		if (value) {
			fx_string_append_cstr(value_str, value);
		}

		fx_hashtable_put(
			env,
			&FX_VALUE_OBJECT(name_str),
			&FX_VALUE_OBJECT(value_str));

		fx_string_unref(name_str);
		fx_string_unref(value_str);
		free(envstr);
	}

	proc->proc_environment = env;

	fx_register_global(self);
	return self;
}

fx_status fx_process_start(fx_process *proc)
{
	FX_CLASS_DISPATCH_STATIC_0(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_start,
		proc);
}

fx_status fx_process_wait(fx_process *proc, int *out_result)
{
	FX_CLASS_DISPATCH_STATIC(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_wait,
		proc,
		out_result);
}

fx_status fx_process_kill(fx_process *proc)
{
	FX_CLASS_DISPATCH_STATIC_0(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_kill,
		proc);
}

const fx_hashtable *fx_process_get_environment(const fx_process *proc)
{
	FX_CLASS_DISPATCH_STATIC_0(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_get_environment,
		proc);
}

fx_stream *fx_process_get_stdin(fx_process *proc)
{
	FX_CLASS_DISPATCH_STATIC_0(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_get_stdin,
		proc);
}

fx_stream *fx_process_get_stdout(fx_process *proc)
{
	FX_CLASS_DISPATCH_STATIC_0(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_get_stdout,
		proc);
}

fx_stream *fx_process_get_stderr(fx_process *proc)
{
	FX_CLASS_DISPATCH_STATIC_0(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_get_stderr,
		proc);
}

void fx_process_close_stdin(fx_process *proc)
{
	FX_CLASS_DISPATCH_STATIC_V0(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_close_stdin,
		proc);
}

void fx_process_close_stdout(fx_process *proc)
{
	FX_CLASS_DISPATCH_STATIC_V0(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_close_stdout,
		proc);
}

void fx_process_close_stderr(fx_process *proc)
{
	FX_CLASS_DISPATCH_STATIC_V0(
		FX_DIAGNOSTICS_TYPE_PROCESS,
		process_close_stderr,
		proc);
}

/*** VIRTUAL FUNCTIONS ********************************************************/

static void process_init(fx_object *obj, void *priv)
{
}

static void process_fini(fx_object *obj, void *priv)
{
	struct fx_process_p *proc = priv;
	fx_array_unref(proc->proc_args);
	fx_iostream_unref(proc->proc_stdin);
	fx_iostream_unref(proc->proc_stdout);
	fx_iostream_unref(proc->proc_stderr);
	fx_string_unref(proc->proc_exec_path);
	fx_hashtable_unref(proc->proc_environment);
}

/*** ITERATOR DEFINITION ******************************************************/

static enum fx_status process_iterator_move_next(const fx_iterator *obj)
{
	return FX_ERR_NO_DATA;
}

static const fx_value *process_iterator_get_value(const fx_iterator *obj)
{
	return NULL;
}

/*** CLASS DEFINITION *********************************************************/

FX_TYPE_CLASS_BEGIN(fx_process)
	FX_TYPE_VTABLE_INTERFACE_BEGIN(fx_object, FX_TYPE_OBJECT)
		FX_INTERFACE_ENTRY(to_string) = NULL;
	FX_TYPE_VTABLE_INTERFACE_END(fx_object, FX_TYPE_OBJECT)
FX_TYPE_CLASS_END(fx_process)

FX_TYPE_DEFINITION_BEGIN(fx_process)
	FX_TYPE_ID(0x7334594f, 0xa1c3, 0x4715, 0xab69, 0x68a709e1b64b);
	FX_TYPE_NAME("fx.diagnostics.process");
	FX_TYPE_CLASS(fx_process_class);
	FX_TYPE_INSTANCE_PRIVATE(struct fx_process_p);
	FX_TYPE_INSTANCE_INIT(process_init);
	FX_TYPE_INSTANCE_FINI(process_fini);
FX_TYPE_DEFINITION_END(fx_process)

FX_TYPE_CLASS_BEGIN(fx_process_iterator)
	FX_TYPE_VTABLE_INTERFACE_BEGIN(fx_object, FX_TYPE_OBJECT)
		FX_INTERFACE_ENTRY(to_string) = NULL;
	FX_TYPE_VTABLE_INTERFACE_END(fx_object, FX_TYPE_OBJECT)

	FX_TYPE_VTABLE_INTERFACE_BEGIN(fx_iterator, FX_TYPE_ITERATOR)
		FX_INTERFACE_ENTRY(it_move_next) = process_iterator_move_next;
		FX_INTERFACE_ENTRY(it_get_value) = process_iterator_get_value;
	FX_TYPE_VTABLE_INTERFACE_END(fx_iterator, FX_TYPE_ITERATOR)
FX_TYPE_CLASS_END(fx_process_iterator)

FX_TYPE_DEFINITION_BEGIN(fx_process_iterator)
	FX_TYPE_ID(0x67eb13b6, 0x25d1, 0x424a, 0xb136, 0x871a07829089);
	FX_TYPE_NAME("fx.diagnostics.process.iterator");
	FX_TYPE_EXTENDS(FX_TYPE_ITERATOR);
	FX_TYPE_CLASS(fx_process_iterator_class);
	FX_TYPE_INSTANCE_PRIVATE(struct fx_process_iterator_p);
FX_TYPE_DEFINITION_END(fx_process_iterator)