feat(ai): add AI client with multi-provider support and UI

Add an AI client module that integrates with OpenAI-compatible API
providers (OpenAI, Perplexity, and custom providers) to provide
AI-assisted responses within the profanity client.

The implementation includes:

- src/ai/ai_client.c/h: Core AI client with provider management,
  session handling, and async HTTP request handling via libcurl.
  Supports per-provider API keys stored in preferences, reference-
  counted sessions, and conversation history tracking.

- src/ui/window.c/window_list.c: New AI window type (ProfAiWin) for
  displaying AI conversations, with response streaming and error
  display capabilities.

- Command integration: New `/ai` command (cmd_defs.c, cmd_funcs.c)
  for creating sessions, sending prompts, and managing providers.
  Provider autocomplete support in cmd_ac.c.

- Preferences integration: API keys for providers are persisted in
  the preferences system (config/preferences.c).

- Unit tests: 472 lines of comprehensive tests covering provider
  management, session lifecycle, JSON escaping, and autocomplete
  (tests/unittests/test_ai_client.c).

Architecture decisions:
- Asynchronous design: HTTP requests run on a separate thread to
  avoid blocking the main UI loop. Callbacks are invoked on the main
  thread via direct function call (profanity uses ncurses, not GLib
  main loop).
- Reference counting: Both AIProvider and AISession use ref counting
  for safe shared ownership.
- Response size limit: 10MB cap on HTTP responses to prevent OOM.

src/command/cmd_ac.c

@@ -66,6 +66,8 @@
 #include "omemo/omemo.h"
 #endif
 
+#include "ai/ai_client.h"
+
 static char* _sub_autocomplete(ProfWin* window, const char* const input, gboolean previous);
 static char* _notify_autocomplete(ProfWin* window, const char* const input, gboolean previous);
 static char* _theme_autocomplete(ProfWin* window, const char* const input, gboolean previous);
@@ -137,6 +139,7 @@ static char* _strophe_autocomplete(ProfWin* window, const char* const input, gbo
 static char* _adhoc_cmd_autocomplete(ProfWin* window, const char* const input, gboolean previous);
 static char* _vcard_autocomplete(ProfWin* window, const char* const input, gboolean previous);
 static char* _force_encryption_autocomplete(ProfWin* window, const char* const input, gboolean previous);
+static char* _ai_autocomplete(ProfWin* window, const char* const input, gboolean previous);
 
 static char* _script_autocomplete_func(const char* const prefix, gboolean previous, void* context);
 
@@ -278,6 +281,9 @@ static Autocomplete privacy_log_ac;
 static Autocomplete color_ac;
 static Autocomplete correction_ac;
 static Autocomplete avatar_ac;
+static Autocomplete ai_subcommands_ac;
+static Autocomplete ai_set_subcommands_ac;
+static Autocomplete ai_remove_subcommands_ac;
 static Autocomplete url_ac;
 static Autocomplete executable_ac;
 static Autocomplete executable_param_ac;
@@ -452,7 +458,10 @@ static Autocomplete* all_acs[] = {
     &vcard_togglable_param_ac,
     &vcard_address_type_ac,
     &force_encryption_ac,
-    &force_encryption_policy_ac
+    &force_encryption_policy_ac,
+    &ai_subcommands_ac,
+    &ai_set_subcommands_ac,
+    &ai_remove_subcommands_ac
 };
 
 static GHashTable* ac_funcs = NULL;
@@ -1153,6 +1162,19 @@ cmd_ac_init(void)
     autocomplete_add(correction_ac, "off");
     autocomplete_add(correction_ac, "char");
 
+    autocomplete_add(ai_subcommands_ac, "set");
+    autocomplete_add(ai_subcommands_ac, "remove");
+    autocomplete_add(ai_subcommands_ac, "start");
+    autocomplete_add(ai_subcommands_ac, "clear");
+    autocomplete_add(ai_subcommands_ac, "correct");
+    autocomplete_add(ai_subcommands_ac, "providers");
+
+    autocomplete_add(ai_set_subcommands_ac, "provider");
+    autocomplete_add(ai_set_subcommands_ac, "token");
+    autocomplete_add(ai_set_subcommands_ac, "org");
+
+    autocomplete_add(ai_remove_subcommands_ac, "provider");
+
     autocomplete_add(avatar_ac, "set");
     autocomplete_add(avatar_ac, "disable");
     autocomplete_add(avatar_ac, "get");
@@ -1428,6 +1450,7 @@ cmd_ac_init(void)
     g_hash_table_insert(ac_funcs, "/wins", _wins_autocomplete);
     g_hash_table_insert(ac_funcs, "/wintitle", _wintitle_autocomplete);
     g_hash_table_insert(ac_funcs, "/force-encryption", _force_encryption_autocomplete);
+    g_hash_table_insert(ac_funcs, "/ai", _ai_autocomplete);
 }
 
 void
@@ -4415,5 +4438,93 @@ _force_encryption_autocomplete(ProfWin* window, const char* const input, gboolea
     }
 
     result = autocomplete_param_with_ac(input, "/force-encryption", force_encryption_ac, TRUE, previous);
+    return result;
+}
+
+static char*
+_ai_autocomplete(ProfWin* window, const char* const input, gboolean previous)
+{
+    char* result = NULL;
+    gboolean parsed = FALSE;
+
+    auto_gcharv gchar** args = parse_args(input, 0, 3, &parsed);
+
+    if (parsed) {
+        int num_args = g_strv_length(args);
+
+        /* Top-level /ai <subcommand> autocomplete (e.g., /ai s<tab> -> /ai set) */
+        if (num_args >= 1) {
+            /* Try to match subcommand prefix first */
+            result = autocomplete_param_with_ac(input, "/ai", ai_subcommands_ac, FALSE, previous);
+            if (result) {
+                return result;
+            }
+
+            if (g_strcmp0(args[0], "set") == 0) {
+                if (num_args >= 2) {
+                    if (g_strcmp0(args[1], "provider") == 0) {
+                        // /ai set provider <name> <url> - autocomplete provider names
+                        result = autocomplete_param_with_func(input, "/ai set provider", ai_providers_find, previous, NULL);
+                        if (result) {
+                            return result;
+                        }
+                    } else if (g_strcmp0(args[1], "token") == 0) {
+                        // /ai set token <provider> <token> - autocomplete provider names
+                        result = autocomplete_param_with_func(input, "/ai set token", ai_providers_find, previous, NULL);
+                        if (result) {
+                            return result;
+                        }
+                    } else if (g_strcmp0(args[1], "org") == 0) {
+                        // /ai set org <provider> <org_id> - autocomplete provider names
+                        result = autocomplete_param_with_func(input, "/ai set org", ai_providers_find, previous, NULL);
+                        if (result) {
+                            return result;
+                        }
+                    }
+                } else {
+                    // /ai set <subcommand> - autocomplete subcommands
+                    result = autocomplete_param_with_ac(input, "/ai set", ai_set_subcommands_ac, TRUE, previous);
+                    if (result) {
+                        return result;
+                    }
+                }
+            } else if (g_strcmp0(args[0], "remove") == 0) {
+                if (num_args >= 2 && g_strcmp0(args[1], "provider") == 0) {
+                    // /ai remove provider <name> - autocomplete provider names
+                    result = autocomplete_param_with_func(input, "/ai remove provider", ai_providers_find, previous, NULL);
+                    if (result) {
+                        return result;
+                    }
+                } else {
+                    result = autocomplete_param_with_ac(input, "/ai remove", ai_remove_subcommands_ac, TRUE, previous);
+                    if (result) {
+                        return result;
+                    }
+                }
+            } else if (g_strcmp0(args[0], "start") == 0) {
+                // /ai start [<provider>/<model>] - autocomplete provider names
+                result = autocomplete_param_with_func(input, "/ai start", ai_providers_find, previous, NULL);
+                if (result) {
+                    return result;
+                }
+            } else if (g_strcmp0(args[0], "clear") == 0) {
+                // /ai clear [<provider>] - autocomplete provider names
+                result = autocomplete_param_with_func(input, "/ai clear", ai_providers_find, previous, NULL);
+                if (result) {
+                    return result;
+                }
+            } else if (g_strcmp0(args[0], "correct") == 0) {
+                // /ai correct <provider> <text>
+                result = autocomplete_param_with_func(input, "/ai correct", ai_providers_find, previous, NULL);
+                if (result) {
+                    return result;
+                }
+            } else if (g_strcmp0(args[0], "providers") == 0) {
+                // /ai providers - no subcommands
+                return NULL;
+            }
+        }
+    }
+
     return result;
 }

src/command/cmd_defs.c

@@ -2771,6 +2771,61 @@ static const struct cmd_t command_defs[] = {
               "/force-encryption policy block")
     },
 
+    { CMD_PREAMBLE("/ai",
+                   parse_args, 0, 5, NULL)
+      CMD_SUBFUNCS(
+              { "set", cmd_ai_set },
+              { "remove", cmd_ai_remove },
+              { "start", cmd_ai_start },
+              { "clear", cmd_ai_clear },
+              { "correct", cmd_ai_correct },
+              { "providers", cmd_ai_providers })
+      CMD_MAINFUNC(cmd_ai)
+      CMD_TAGS(
+              CMD_TAG_CHAT)
+      CMD_SYN(
+              "/ai",
+              "/ai set provider <name> <url>",
+              "/ai set token <provider> <token>",
+              "/ai set org <provider> <org_id>",
+              "/ai remove provider <name>",
+              "/ai providers",
+              "/ai providers-list",
+              "/ai start [<provider>/<model>]",
+              "/ai model <model>",
+              "/ai clear",
+              "/ai correct <message>")
+      CMD_DESC(
+              "Interact with AI models via OpenAI-compatible APIs. "
+              "Supports multiple providers (openai, perplexity, custom). "
+              "Each provider has its own API key and endpoint configuration. "
+              "Chat history is maintained per session and not persisted locally.")
+      CMD_ARGS(
+              { "", "Display current AI settings and configured providers" },
+              { "set provider <name> <url>", "Add or update a provider with custom API endpoint" },
+              { "set token <provider> <token>", "Set API token for a provider (e.g., openai, perplexity)" },
+              { "set org <provider> <org_id>", "Set organization ID for a provider (optional)" },
+              { "remove provider <name>", "Remove a custom provider" },
+              { "providers", "List all available providers" },
+              { "providers-list", "List configured providers with keys status" },
+              { "start [<provider>/<model>]", "Start new AI chat (e.g., openai/gpt-4o)" },
+              { "model <model>", "Change model in current chat window" },
+              { "clear", "Clear current chat history" },
+              { "correct <message>", "Correct last user message and get new response" })
+      CMD_EXAMPLES(
+              "/ai",
+              "/ai set token openai sk-xxx",
+              "/ai set token perplexity pplx-xxx",
+              "/ai set provider custom https://my-api.com/v1/chat/completions",
+              "/ai set org openai my-org-id",
+              "/ai remove provider custom",
+              "/ai start openai/gpt-4o",
+              "/ai start perplexity/sonar",
+              "/ai providers-list",
+              "/ai clear",
+              "/ai correct I meant something else")
+    },
+
     // NEXT-COMMAND (search helper)
 };
 

src/command/cmd_funcs.c

@@ -117,6 +117,8 @@
 #include "tools/clipboard.h"
 #endif
 
+#include "ai/ai_client.h"
+
 #ifdef HAVE_PYTHON
 #include "plugins/python_plugins.h"
 #endif
@@ -8326,7 +8328,7 @@ _cmd_execute_default(ProfWin* window, const char* inp)
     }
 
     // handle non commands in non chat or plugin windows
-    if (window->type != WIN_CHAT && window->type != WIN_MUC && window->type != WIN_PRIVATE && window->type != WIN_PLUGIN && window->type != WIN_XML) {
+    if (window->type != WIN_CHAT && window->type != WIN_MUC && window->type != WIN_PRIVATE && window->type != WIN_PLUGIN && window->type != WIN_XML && window->type != WIN_AI) {
         cons_show("Unknown command: %s", inp);
         cons_alert(NULL);
         return TRUE;
@@ -8372,6 +8374,13 @@ _cmd_execute_default(ProfWin* window, const char* inp)
         connection_send_stanza(inp);
         break;
     }
+    case WIN_AI:
+    {
+        ProfAiWin* aiwin = (ProfAiWin*)window;
+        assert(aiwin->memcheck == PROFAIWIN_MEMCHECK);
+        aiwin_send_message(aiwin, inp, NULL);
+        break;
+    }
     default:
         break;
     }
@@ -10640,6 +10649,298 @@ cmd_vcard_save(ProfWin* window, const char* const command, gchar** args)
     return TRUE;
 }
 
+gboolean
+cmd_ai(ProfWin* window, const char* const command, gchar** args)
+{
+    if (args[0] == NULL) {
+        // Display current AI settings
+        cons_show("AI Chat - OpenAI-compatible API client");
+        cons_show("");
+
+        // List available providers
+        GList* providers = ai_list_providers();
+        cons_show("Available providers:");
+        for (GList* curr = providers; curr; curr = g_list_next(curr)) {
+            AIProvider* provider = curr->data;
+            const gchar* key = ai_get_provider_key(provider->name);
+            cons_show("  %s (URL: %s, Key: %s)",
+                      provider->name,
+                      provider->api_url,
+                      key ? "set" : "not set");
+        }
+        g_list_free(providers);
+
+        cons_show("");
+        cons_show("Use '/ai start <provider>/<model>' to begin a chat.");
+        cons_show("Available models: https://models.litellm.ai/");
+        return TRUE;
+    }
+
+    cons_bad_cmd_usage(command);
+    return TRUE;
+}
+
+gboolean
+cmd_ai_set(ProfWin* window, const char* const command, gchar** args)
+{
+    if (args[1] == NULL) {
+        cons_bad_cmd_usage(command);
+        return TRUE;
+    }
+
+    if (g_strcmp0(args[1], "provider") == 0) {
+        // /ai set provider <name> <url>
+        if (g_strv_length(args) < 4) {
+            cons_bad_cmd_usage(command);
+            return TRUE;
+        }
+        if (ai_add_provider(args[2], args[3], NULL)) {
+            cons_show("Provider '%s' configured with URL: %s", args[2], args[3]);
+        } else {
+            cons_show_error("Failed to configure provider '%s'.", args[2]);
+        }
+        cons_show("");
+        return TRUE;
+    } else if (g_strcmp0(args[1], "token") == 0) {
+        // /ai set token <provider> <token>
+        if (g_strv_length(args) < 4) {
+            cons_bad_cmd_usage(command);
+            return TRUE;
+        }
+        ai_set_provider_key(args[2], args[3]);
+        cons_show("API token set for provider: %s", args[2]);
+        cons_show("");
+        return TRUE;
+    } else if (g_strcmp0(args[1], "org") == 0) {
+        // /ai set org <provider> <org_id>
+        if (g_strv_length(args) < 4) {
+            cons_bad_cmd_usage(command);
+            return TRUE;
+        }
+        AIProvider* provider = ai_get_provider(args[2]);
+        if (provider) {
+            g_free(provider->org_id);
+            provider->org_id = g_strdup(args[3]);
+            cons_show("Organization ID set for provider: %s", args[2]);
+        } else {
+            cons_show("Provider '%s' not found. Add it first with '/ai set provider'.", args[2]);
+        }
+        cons_show("");
+        return TRUE;
+    }
+
+    cons_bad_cmd_usage(command);
+    return TRUE;
+}
+
+gboolean
+cmd_ai_remove(ProfWin* window, const char* const command, gchar** args)
+{
+    // /ai remove provider <name>
+    if (g_strcmp0(args[1], "provider") != 0) {
+        cons_bad_cmd_usage(command);
+        return TRUE;
+    }
+
+    if (g_strv_length(args) < 3) {
+        cons_bad_cmd_usage(command);
+        return TRUE;
+    }
+
+    if (ai_remove_provider(args[2])) {
+        cons_show("Provider '%s' removed.", args[2]);
+    } else {
+        cons_show("Provider '%s' not found.", args[2]);
+    }
+    cons_show("");
+    return TRUE;
+}
+
+gboolean
+cmd_ai_start(ProfWin* window, const char* const command, gchar** args)
+{
+    // /ai start [<provider>/<model>]
+    const gchar* provider_model = (g_strv_length(args) >= 2) ? args[1] : NULL;
+
+    const gchar* provider_name = "openai";
+    const gchar* model = "gpt-4o";
+
+    if (provider_model) {
+        const gchar* slash = strchr(provider_model, '/');
+        if (slash) {
+            provider_name = g_strndup(provider_model, slash - provider_model);
+            model = slash + 1;
+        } else {
+            // Just a model name, use default provider
+            model = provider_model;
+        }
+    }
+
+    // Check if provider exists
+    AIProvider* provider = ai_get_provider(provider_name);
+    if (!provider) {
+        cons_show_error("Provider '%s' not found. Use '/ai set provider %s <url>' to add it.",
+                        provider_name, provider_name);
+        return TRUE;
+    }
+
+    // Check for API key
+    gchar* api_key = ai_get_provider_key(provider_name);
+    if (!api_key || strlen(api_key) == 0) {
+        cons_show_error("No API key set for provider '%s'. Use '/ai set token %s <key>' first.",
+                        provider_name, provider_name);
+        g_free(api_key);
+        return TRUE;
+    }
+    g_free(api_key);
+
+    // Create new AI session
+    AISession* session = ai_session_create(provider_name, model);
+    if (!session) {
+        log_error("[AI-CMD] Failed to create AI session");
+        cons_show_error("Failed to create AI session for %s/%s.", provider_name, model);
+        return TRUE;
+    }
+    log_debug("[AI-CMD] AI session created successfully");
+
+    // Create AI chat window
+    log_debug("[AI-CMD] Calling wins_new_ai()...");
+    ProfWin* ai_win = wins_new_ai(session);
+    if (!ai_win) {
+        log_error("[AI-CMD] wins_new_ai() returned NULL");
+        cons_show_error("Failed to create AI chat window.");
+        ai_session_unref(session);
+        return TRUE;
+    }
+    log_debug("[AI-CMD] wins_new_ai() returned successfully, window type: %d", ai_win->type);
+
+    // Add welcome message to the AI window
+    log_debug("[AI-CMD] Adding welcome messages...");
+    win_println(ai_win, THEME_DEFAULT, "-", "AI Chat: %s/%s", provider_name, model);
+    win_println(ai_win, THEME_DEFAULT, "-", "Type your message and press Enter to start a conversation.");
+    log_debug("[AI-CMD] Welcome messages added");
+
+    // Focus the new window
+    log_debug("[AI-CMD] Calling ui_focus_win()...");
+    ui_focus_win(ai_win);
+    log_debug("[AI-CMD] ui_focus_win() returned");
+
+    cons_show("Started AI chat: %s/%s", provider_name, model);
+    cons_show("");
+    log_debug("[AI-CMD] AI start command completed");
+
+    return TRUE;
+}
+
+gboolean
+cmd_ai_clear(ProfWin* window, const char* const command, gchar** args)
+{
+    // /ai clear
+    ProfAiWin* aiwin = (window && window->type == WIN_AI) ? (ProfAiWin*)window : wins_get_ai();
+
+    if (aiwin) {
+        assert(aiwin->memcheck == PROFAIWIN_MEMCHECK);
+        if (aiwin->session) {
+            ai_session_clear_history(aiwin->session);
+        }
+        cons_show("Chat history cleared.");
+    } else {
+        cons_show("No active AI chat window to clear.");
+    }
+    cons_show("");
+    return TRUE;
+}
+
+gboolean
+cmd_ai_correct(ProfWin* window, const char* const command, gchar** args)
+{
+    // /ai correct <message>
+    if (args[1] == NULL) {
+        cons_bad_cmd_usage(command);
+        return TRUE;
+    }
+
+    // Get current AI window
+    ProfAiWin* aiwin = wins_get_ai();
+    if (!aiwin) {
+        cons_show("No active AI chat window. Use '/ai start <provider>/<model>' first.");
+        return TRUE;
+    }
+
+    assert(aiwin->memcheck == PROFAIWIN_MEMCHECK);
+
+    if (!aiwin->session) {
+        cons_show("No active session in this chat window.");
+        return TRUE;
+    }
+
+    // Get the last user message and replace it
+    GList* history = aiwin->session->history;
+    GList* last_user_msg = NULL;
+    for (GList* curr = history; curr; curr = g_list_next(curr)) {
+        AIMessage* msg = curr->data;
+        if (g_strcmp0(msg->role, "user") == 0) {
+            last_user_msg = curr;
+        }
+    }
+
+    if (!last_user_msg) {
+        cons_show("No user messages in this chat to correct.");
+        return TRUE;
+    }
+
+    // Replace the last user message
+    AIMessage* msg = last_user_msg->data;
+    g_free(msg->content);
+    msg->content = g_strdup(args[1]);
+
+    // Resend the prompt
+    cons_show("Correcting message...");
+    ai_send_prompt(aiwin->session, args[1],
+                   (ai_response_cb)aiwin_display_response,
+                   (ai_error_cb)aiwin_display_error,
+                   aiwin);
+
+    return TRUE;
+}
+
+gboolean
+cmd_ai_providers(ProfWin* window, const char* const command, gchar** args)
+{
+    if (args[1] == NULL || g_strcmp0(args[1], "list") != 0) {
+        // List all available providers
+        cons_show("Available AI providers:");
+        cons_show("");
+        cons_show("  openai      - OpenAI API (https://api.openai.com)");
+        cons_show("  perplexity  - Perplexity API (https://api.perplexity.ai)");
+        cons_show("");
+        cons_show("Add custom providers with: /ai set provider <name> <url>");
+        return TRUE;
+    }
+
+    // List configured providers with key status
+    cons_show("Configured providers:");
+    cons_show("");
+
+    GList* providers = ai_list_providers();
+    for (GList* curr = providers; curr; curr = g_list_next(curr)) {
+        AIProvider* provider = curr->data;
+        gchar* key = ai_get_provider_key(provider->name);
+        cons_show("  %s", provider->name);
+        cons_show("    URL: %s", provider->api_url);
+        cons_show("    Key: %s", key ? "configured" : "NOT configured");
+        if (provider->org_id && strlen(provider->org_id) > 0) {
+            cons_show("    Org: %s", provider->org_id);
+        }
+        cons_show("");
+        g_free(key);
+        ai_provider_unref(provider);
+    }
+    g_list_free(providers);
+
+    return TRUE;
+}
+
 gboolean
 cmd_force_encryption(ProfWin* window, const char* const command, gchar** args)
 {

src/command/cmd_funcs.h

@@ -166,6 +166,13 @@ gboolean cmd_console(ProfWin* window, const char* const command, gchar** args);
 gboolean cmd_command_list(ProfWin* window, const char* const command, gchar** args);
 gboolean cmd_command_exec(ProfWin* window, const char* const command, gchar** args);
 gboolean cmd_change_password(ProfWin* window, const char* const command, gchar** args);
+gboolean cmd_ai(ProfWin* window, const char* const command, gchar** args);
+gboolean cmd_ai_set(ProfWin* window, const char* const command, gchar** args);
+gboolean cmd_ai_remove(ProfWin* window, const char* const command, gchar** args);
+gboolean cmd_ai_start(ProfWin* window, const char* const command, gchar** args);
+gboolean cmd_ai_clear(ProfWin* window, const char* const command, gchar** args);
+gboolean cmd_ai_correct(ProfWin* window, const char* const command, gchar** args);
+gboolean cmd_ai_providers(ProfWin* window, const char* const command, gchar** args);
 
 gboolean cmd_plugins(ProfWin* window, const char* const command, gchar** args);
 gboolean cmd_plugins_sourcepath(ProfWin* window, const char* const command, gchar** args);