support lookups via language servers (LSP)master-fmsbw-ci

* The main interface is the `FT` command.
  `FT` was an undocumented Video TECO command for etags/ctags lookups.
  I don't want to exactly copy its interface, though.
* `FT` allows looking up symbol names,
  definitions and references.
* ctags will be supported via ctags-lsp.
  LSP support is more powerful though and works without
  regenerating TAGS files all the time.
  The LSP will also allow you to customize auto-completions
  using SciTECO itself (i.e. by writing a language server
  in SciTECO).
* For multiple results, `FT$` can be used to cycle through
  results - this should mimic repeated `S$` or `N$`.
* `:FT...$` does a fuzzy search. IMHO it's not important
  to return a status integer instead. `FT` will only
  really be used in interactive mode.
* Document synchronization is supported via hooks from
  ring.c and via Scintilla notifications.
* Currently, the LSP communication is based on blocking
  GIOChannels. This means that a misbehaving hanging
  server could "lock up" the entire editor (FIXME).
  Only on ncurses you can always kill the subprocess by
  pressing CTRL+C.
  We need helper functions in spawn.c to read and write
  with interruptions.
* The textDocument/didChange notification transmits
  not only all edits, but all files' contents as well
  during initial synchronization.
  Therefore it is optimized to write and JSON-escape
  data without copying them around in memory and without
  destroying the buffer gap.
* Use $SCITECO_LSP to configure the language server.
  You can also use `tee` to capture stdin and stdout.
  Perhaps $SCITECO_LSP should be saved in .teco_session,
  so you can change it between projects?
* $SCITECO_LSP_ROOT is used to point to the project's
  root directory. session.tes will set it up automatically.

1 files changed, 57 insertions, 0 deletions

diff --git a/src/cmdline.c b/src/cmdline.c
index 7fe044c..572b159 100644
--- a/src/cmdline.c
+++ b/src/cmdline.c
@@ -53,6 +53,7 @@
 #include "error.h"
 #include "qreg.h"
 #include "glob.h"
+#include "lsp.h"
 #include "cmdline.h"
 
 #if defined(HAVE_MALLOC_TRIM) && !defined(HAVE_DECL_MALLOC_TRIM)
@@ -1506,6 +1507,62 @@ teco_state_help_insert_completion(teco_machine_main_t *ctx, teco_string_t str, G
 	return teco_cmdline_insert(str_escaped.data, str_escaped.len, error);
 }
 
+gboolean
+teco_state_lsp_lookup_process_edit_cmd(teco_machine_main_t *ctx, teco_machine_t *parent_ctx,
+                                       gunichar key, GError **error)
+{
+	teco_machine_stringbuilding_t *stringbuilding_ctx = &ctx->expectstring.machine;
+	teco_state_t *stringbuilding_current = stringbuilding_ctx->parent.current;
+
+	/*
+	 * NOTE: We don't just define teco_state_stringbuilding_start_process_edit_cmd(),
+	 * as it would be hard to subclass/overwrite for different main machine states.
+	 */
+	if (!stringbuilding_current->is_start)
+		return stringbuilding_current->process_edit_cmd_cb(&stringbuilding_ctx->parent, &ctx->parent, key, error);
+
+	switch (key) {
+	case '\t': { /* autocomplete LSP symbol */
+		if (teco_cmdline.modifier_enabled)
+			break;
+
+		if (teco_interface_popup_is_shown()) {
+			/* cycle through popup pages */
+			teco_interface_popup_scroll();
+			return TRUE;
+		}
+
+		if (teco_string_contains(ctx->expectstring.string, '\0'))
+			/* LSP symbol must not contain null-byte */
+			return TRUE;
+
+		g_auto(teco_string_t) new_chars, new_chars_escaped;
+		gboolean unambiguous = teco_lsp_symbol_auto_complete(ctx->expectstring.string.data, &new_chars);
+		teco_machine_stringbuilding_escape(stringbuilding_ctx, new_chars.data, new_chars.len, &new_chars_escaped);
+		if (unambiguous && ctx->expectstring.nesting == 1)
+			teco_string_append_wc(&new_chars_escaped,
+			                      ctx->expectstring.machine.escape_char == '{' ? '}' : ctx->expectstring.machine.escape_char);
+
+		return new_chars_escaped.len ? teco_cmdline_insert(new_chars_escaped.data, new_chars_escaped.len, error) : TRUE;
+	}
+	}
+
+	return stringbuilding_current->process_edit_cmd_cb(&stringbuilding_ctx->parent, &ctx->parent, key, error);
+}
+
+gboolean
+teco_state_lsp_lookup_insert_completion(teco_machine_main_t *ctx, teco_string_t str, GError **error)
+{
+	teco_machine_stringbuilding_t *stringbuilding_ctx = &ctx->expectstring.machine;
+
+	g_auto(teco_string_t) str_escaped;
+	teco_machine_stringbuilding_escape(stringbuilding_ctx, str.data, str.len, &str_escaped);
+	if (ctx->expectstring.nesting == 1)
+		teco_string_append_wc(&str_escaped,
+		                      ctx->expectstring.machine.escape_char == '{' ? '}' : ctx->expectstring.machine.escape_char);
+	return teco_cmdline_insert(str_escaped.data, str_escaped.len, error);
+}
+
 /*
  * Command states
  */