Add LSP hover information

defs.h

@@ -19,6 +19,7 @@ enum severity { ERROR = 1, WARNING, INFORMATION, HINT };
 
 // Data types
 enum types { NO_TYPE, INT, UINT };
+static const char *types_str[] = { "void", "int", "unsigned int" };
 
 // Kinds of symbols (maximum 32 different kinds)
 enum kinds { NO_KIND = 0x1, REG = 0x2, LIT = 0x4,

lsp.c

@@ -1,10 +1,12 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <ctype.h>
 #include <cjson/cJSON.h>
 #include "lsp.h"
 #define MAX_HEADER_FIELD_LEN 100
 void parse(cJSON *diagnostics, const char *text);
+char* symbol_info(const char *symbol_name, const char *text);
 
 void lsp_event_loop(void) {
   for(;;) {
@@ -93,6 +95,9 @@ void json_rpc(const cJSON *request) {
   else if(strcmp(method, "textDocument/didChange") == 0) {
     lsp_text_sync("didChange", params_json);
   }
+  else if(strcmp(method, "textDocument/hover") == 0) {
+    lsp_hover(id, params_json);
+  }
 }
 
 void lsp_send_response(int id, cJSON *result) {
@@ -133,6 +138,7 @@ void lsp_initialize(int id) {
   cJSON *result = cJSON_CreateObject();
   cJSON *capabilities = cJSON_CreateObject();
   cJSON_AddNumberToObject(capabilities, "textDocumentSync", 1);
+  cJSON_AddBoolToObject(capabilities, "hoverProvider", 1);
   // TODO add other capabilities
 
   cJSON_AddItemToObject(result, "capabilities", capabilities);
@@ -185,3 +191,66 @@ void lsp_lint(const char *uri, const char *text) {
   parse(diagnostics, text);
   lsp_send_notification("textDocument/publishDiagnostics", params);
 }
+
+char* read_to_string(const char *uri) {
+  // uri + 7 -> skips file://
+  FILE *f = fopen(uri + 7, "r");
+  fseek(f, 0, SEEK_END);
+  unsigned long fsize = ftell(f);
+  rewind(f);
+
+  char *text = malloc(fsize + 1);
+  if(text == NULL)
+    exit(2);
+  fread(text, 1, fsize, f);
+  fclose(f);
+
+  text[fsize] = '\0';
+  return text;
+}
+
+const char* truncate_string(char *text, int line, int character) {
+  int position = 0;
+  for(int i = 0; i < line; i++) {
+    position += strcspn(text + position, "\n") + 1;
+  }
+  position += character;
+  int id_begin = position;
+
+  while(isalnum(*(text + position))) {
+    ++position;
+  }
+  text[position] = '\0';
+
+  return text + id_begin;
+}
+
+void lsp_hover(int id, const cJSON *params_json) {
+  const cJSON *text_document_json = cJSON_GetObjectItem(params_json, "textDocument");
+  const cJSON *uri_json = cJSON_GetObjectItem(text_document_json, "uri");
+  const char *uri = NULL;
+  if(cJSON_IsString(uri_json) && (uri_json->valuestring != NULL)) {
+    uri = uri_json->valuestring;
+  }
+
+  const cJSON *position_json = cJSON_GetObjectItem(params_json, "position");
+  const cJSON *line_json = cJSON_GetObjectItem(position_json, "line");
+  int line;
+  if(cJSON_IsNumber(line_json)) {
+    line = line_json->valueint;
+  }
+  int character;
+  const cJSON *character_json = cJSON_GetObjectItem(position_json, "character");
+  if(cJSON_IsNumber(character_json)) {
+    character = character_json->valueint;
+  }
+
+  char *text = read_to_string(uri);
+  const char *symbol_name  = truncate_string(text, line, character);
+  char *contents = symbol_info(symbol_name, text);
+  free(text);
+
+  cJSON *result = cJSON_CreateObject();
+  cJSON_AddStringToObject(result, "contents", contents);
+  lsp_send_response(id, result);
+}

lsp.h

@@ -49,5 +49,9 @@ void lsp_text_sync(const char *method, const cJSON *params_json);
  * Runs a linter and returns LSP publish diagnostics notification.
  */
 void lsp_lint(const char *uri, const char *text);
+/*
+ * Parses LSP hover request, and returns hover information.
+ */
+void lsp_hover(int id, const cJSON *params_json);
 
 #endif

minic.y

@@ -1,6 +1,6 @@
 %{
   #include <stdio.h>
-  #include <stdbool.h>
+  #include <string.h>
   #include "defs.h"
   #include "symtab.h"
   #include <cjson/cJSON.h>
@@ -267,10 +267,22 @@ void parse(cJSON *diagnostics, const char *text) {
   YY_BUFFER_STATE buffer = yy_scan_string(text);
   yyparse();
   yy_delete_buffer(buffer);
-  clear_symtab();
   _diagnostics = NULL;
 }
 
+char* symbol_info(const char *symbol_name, const char *text) {
+  parse(NULL, text);
+  int idx = lookup_symbol(symbol_name, VAR|PAR|FUN);
+  const char *type = types_str[get_type(idx)];
+  const char *name = get_name(idx);
+
+  char *info = malloc(strlen(type) + strlen(name) + 2);
+  strcpy(info, type);
+  strcat(info, " ");
+  strcat(info, name);
+  return info;
+}
+
 int main() {
   lsp_event_loop();
   return 0;

symtab.c

@@ -65,7 +65,7 @@ int insert_literal(char *str, unsigned type) {
  * Returns index of the found element.
  * If the element is not found, returns -1.
  */
-int lookup_symbol(char *name, unsigned kind) {
+int lookup_symbol(const char *name, unsigned kind) {
   int i;
   for(i = first_empty - 1; i > FUN_REG; i--) {
     if(strcmp(symbol_table[i].name, name) == 0

symtab.h

@@ -32,7 +32,7 @@ int insert_literal(char *str, unsigned type);
  * Returns index of the found element.
  * If the element is not found, returns -1.
  */
-int lookup_symbol(char *name, unsigned kind);
+int lookup_symbol(const char *name, unsigned kind);
 
 // Setters and getters for element fields.
 void     set_name(int index, char *name);