// @TODO:  maximum queue size for requests/responses just in case?

typedef enum {
	LSP_NONE,
	LSP_INITIALIZE,
	LSP_INITIALIZED,
	LSP_OPEN,
	LSP_COMPLETION,
} LSPRequestType;

typedef struct {
	// buffer language
	Language language;
	// these will be free'd.
	char *filename;
	char *file_contents;
} LSPRequestOpen;

typedef struct {
	LSPRequestType type;
	union {
		LSPRequestOpen open;
	} data;
} LSPRequest;

typedef struct {
	Process process;
	u64 request_id;
	JSON *responses;
	SDL_mutex *responses_mutex;
	LSPRequest *requests;
	SDL_mutex *requests_mutex;
	bool initialized; // has the response to the initialize request been sent?
	SDL_Thread *communication_thread;
	SDL_sem *quit_sem;
	char *received_data; // dynamic array
	char error[256];
} LSP;


static void write_request_content(LSP *lsp, const char *content) {
	char header[128];
	size_t content_size = strlen(content);
	strbuf_printf(header, "Content-Length: %zu\r\n\r\n", content_size); 
	#if 0
		printf("\x1b[1m%s%s\x1b[0m\n", header, content);
	#endif
	process_write(&lsp->process, header, strlen(header));
	process_write(&lsp->process, content, content_size);
}

static const char *lsp_language_id(Language lang) {
	switch (lang) {
	case LANG_CONFIG:
	case LANG_TED_CFG:
	case LANG_NONE:
		return "text";
	case LANG_C:
		return "c";
	case LANG_CPP:
		return "cpp";
	case LANG_JAVA:
		return "java";
	case LANG_JAVASCRIPT:
		return "javascript";
	case LANG_MARKDOWN:
		return "markdown";
	case LANG_GO:
		return "go";
	case LANG_RUST:
		return "rust";
	case LANG_PYTHON:
		return "python";
	case LANG_HTML:
		return "html";
	case LANG_TEX:
		return "latex";
	case LANG_COUNT: break;
	}
	assert(0);
	return "text";
}

static void write_request(LSP *lsp, const LSPRequest *request) {
	unsigned long long id = lsp->request_id++;
	
	
	switch (request->type) {
	case LSP_NONE:
		assert(0);
		break;
	case LSP_INITIALIZE: {
		char content[1024];
		strbuf_printf(content,
			"{\"jsonrpc\":\"2.0\",\"id\":%llu,\"method\":\"initialize\",\"params\":{"
				"\"processId\":%d,"
				"\"capabilities\":{}"
		"}}", id, process_get_id());
		write_request_content(lsp, content);
	} break;
	case LSP_INITIALIZED: {
		char content[1024];
		strbuf_printf(content,
			"{\"jsonrpc\":\"2.0\",\"id\":%llu,\"method\":\"initialized\",\"params\":{"
		"}}", id);
		write_request_content(lsp, content);
	} break;
	case LSP_OPEN: {
		const LSPRequestOpen *open = &request->data.open;
		char *escaped_filename = json_escape(open->filename);
		char *did_open = a_sprintf(
			"{\"jsonrpc\":\"2.0\",\"id\":%llu,\"method\":\"textDocument/open\",\"params\":{"
				"textDocument:{"
					"uri:\"file://%s\","
					"languageId:\"%s\","
					"version:1,"
					"text:\"",
			id, escaped_filename, lsp_language_id(open->language));
		free(escaped_filename);
		
		size_t did_open_sz = strlen(did_open) + 2 * strlen(open->file_contents) + 16;
		did_open = realloc(did_open, did_open_sz);
		
		size_t n = json_escape_to(did_open + strlen(did_open),
			did_open_sz - 10 - strlen(did_open),
			open->file_contents);
		char *p = did_open + n;
		sprintf(p, "\"}}}");
		
		free(did_open);
		
		write_request_content(lsp, did_open);
	} break;
	case LSP_COMPLETION: {
		char content[1024];
		// no params needed
		strbuf_printf(content,
			"{\"jsonrpc\":\"2.0\",\"id\":%llu,\"method\":\"initialize\",\"params\":{"
		"}}", id);
		write_request_content(lsp, content);
	} break;
	}
}

// figure out if data begins with a complete LSP response.
static bool has_response(const char *data, size_t data_len, u64 *p_offset, u64 *p_size) {
	const char *content_length = strstr(data, "Content-Length");
	if (!content_length) return false;
	const char *p = content_length + strlen("Content-Length");
	if (!p[0] || !p[1] || !p[2]) return false;
	p += 2;
	size_t size = (size_t)atoll(p);
	*p_size = size;
	const char *header_end = strstr(content_length, "\r\n\r\n");
	if (!header_end) return false;
	header_end += 4;
	u64 offset = (u64)(header_end - data);
	*p_offset = offset;
	return offset + size <= data_len;
}

void lsp_send_request(LSP *lsp, const LSPRequest *request) {
	SDL_LockMutex(lsp->requests_mutex);
	arr_add(lsp->requests, *request);
	SDL_UnlockMutex(lsp->requests_mutex);
}

// receive responses from LSP, up to max_size bytes.
static void lsp_receive(LSP *lsp, size_t max_size) {

	{
		// read stderr. if all goes well, we shouldn't get anything over stderr.
		char stderr_buf[1024] = {0};
		for (size_t i = 0; i < (max_size + sizeof stderr_buf) / sizeof stderr_buf; ++i) {
			ssize_t nstderr = process_read_stderr(&lsp->process, stderr_buf, sizeof stderr_buf - 1);
			if (nstderr > 0) {
				// uh oh
				stderr_buf[nstderr] = '\0';
				fprintf(stderr, "\x1b[1m\x1b[93m%s\x1b[0m", stderr_buf);
			} else {
				break;
			}
		}
	}

	size_t received_so_far = arr_len(lsp->received_data);
	arr_reserve(lsp->received_data, received_so_far + max_size + 1);
	long long bytes_read = process_read(&lsp->process, lsp->received_data + received_so_far, max_size);
	if (bytes_read <= 0) {
		// no data
		return;
	}
	received_so_far += (size_t)bytes_read;
	// kind of a hack. this is needed because arr_set_len zeroes the data.
	arr_hdr_(lsp->received_data)->len = (u32)received_so_far;
	lsp->received_data[received_so_far] = '\0';// null terminate
	#if 0
	printf("\x1b[3m%s\x1b[0m\n",lsp->received_data);
	#endif
	
	u64 response_offset=0, response_size=0;
	while (has_response(lsp->received_data, received_so_far, &response_offset, &response_size)) {
		char *copy = strn_dup(lsp->received_data + response_offset, response_size);
		JSON json = {0};
		json_parse(&json, copy);
		assert(json.text == copy);
		json.is_text_copied = true;
		
		JSONValue result = json_get(&json, "result");
		if (result.type == JSON_UNDEFINED) {
			// uh oh
			JSONValue error = json_get(&json, "error.message");
			if (error.type == JSON_STRING) {
				json_string_get(&json, &error.val.string, lsp->error, sizeof lsp->error);
			} else {
				strbuf_printf(lsp->error, "Server error (no message)");
			}
		} else {
			SDL_LockMutex(lsp->responses_mutex);
			arr_add(lsp->responses, json);
			SDL_UnlockMutex(lsp->responses_mutex);
		}
		
		size_t leftover_data_len = arr_len(lsp->received_data) - (response_offset + response_size);
		memmove(lsp->received_data, lsp->received_data + response_offset + response_size,
			leftover_data_len);
		arr_set_len(lsp->received_data, leftover_data_len);
		arr_reserve(lsp->received_data, leftover_data_len + 1);
		lsp->received_data[leftover_data_len] = '\0';
	}
}

static void free_request(LSPRequest *r) {
	switch (r->type) {
	case LSP_NONE:
		assert(0);
		break;
	case LSP_INITIALIZE:
	case LSP_INITIALIZED:
	case LSP_COMPLETION:
		break;
	case LSP_OPEN: {
		LSPRequestOpen *open = &r->data.open;
		free(open->filename);
		free(open->file_contents);
		} break;
	}
}

// send requests.
static bool lsp_send(LSP *lsp) {
	if (!lsp->initialized) {
		// don't send anything before the server is initialized.
		return false;
	}
	
	LSPRequest *requests = NULL;
	SDL_LockMutex(lsp->requests_mutex);
	size_t n_requests = arr_len(lsp->requests);
	requests = calloc(n_requests, sizeof *requests);
	memcpy(requests, lsp->requests, n_requests * sizeof *requests);
	SDL_UnlockMutex(lsp->requests_mutex);

	bool quit = false;
	for (size_t i = 0; i < n_requests; ++i) {
		LSPRequest *r = &requests[i];
		if (!quit) {
			// this could slow down lsp_free if there's a gigantic request.
			// whatever.
			write_request(lsp, r);
		}
		free_request(r);
		
		if (SDL_SemTryWait(lsp->quit_sem) == 0) {
			quit = true;
			// important that we don't break here so all the requests get freed.
		}
	}

	free(requests);
	return quit;
}


// Do any necessary communication with the LSP.
// This writes requests and reads (and parses) responses.
static int lsp_communication_thread(void *data) {
	LSP *lsp = data;
	while (1) {
		bool quit = lsp_send(lsp);
		if (quit) break;
		
		lsp_receive(lsp, (size_t)10<<20);
		if (SDL_SemWaitTimeout(lsp->quit_sem, 5) == 0)
			break;	
	}
	return 0;
}

bool lsp_create(LSP *lsp, const char *analyzer_command) {
	ProcessSettings settings = {
		.stdin_blocking = true,
		.stdout_blocking = false,
		.stderr_blocking = false,
		.separate_stderr = true,
	};
	process_run_ex(&lsp->process, analyzer_command, &settings);
	LSPRequest initialize = {
		.type = LSP_INITIALIZE
	};
	// immediately send the request rather than queueing it.
	// this is a small request, so it shouldn't be a problem.
	write_request(lsp, &initialize);
	
	lsp->quit_sem = SDL_CreateSemaphore(0);	
	lsp->responses_mutex = SDL_CreateMutex();
	lsp->communication_thread = SDL_CreateThread(lsp_communication_thread, "LSP communicate", lsp);
	return true;
}

bool lsp_next_response(LSP *lsp, JSON *json) {
	bool any = false;
	SDL_LockMutex(lsp->responses_mutex);
	if (arr_len(lsp->responses)) {
		*json = lsp->responses[0];
		arr_remove(lsp->responses, 0);
		any = true;
	}
	SDL_UnlockMutex(lsp->responses_mutex);
	return any;
}

void lsp_free(LSP *lsp) {
	SDL_SemPost(lsp->quit_sem);
	SDL_WaitThread(lsp->communication_thread, NULL);
	SDL_DestroySemaphore(lsp->quit_sem);
	process_kill(&lsp->process);
	arr_free(lsp->received_data);
}