story-kit: merge 285_story_matrix_bot_help_command_lists_available_bot_commands

server/src/matrix/commands.rs

@@ -0,0 +1,318 @@
+//! Bot-level command registry for the Matrix bot.
+//!
+//! Commands registered here are handled directly by the bot without invoking
+//! the LLM. The registry is the single source of truth — the `help` command
+//! iterates it automatically so new commands appear in the help output as soon
+//! as they are added.
+
+/// A bot-level command that is handled without LLM invocation.
+pub struct BotCommand {
+    /// The command keyword (e.g., `"help"`). Always lowercase.
+    pub name: &'static str,
+    /// Short description shown in help output.
+    pub description: &'static str,
+    /// Handler that produces the response text (Markdown).
+    pub handler: fn(&CommandContext) -> String,
+}
+
+/// Context passed to command handlers.
+pub struct CommandContext<'a> {
+    /// The bot's display name (e.g., "Timmy").
+    pub bot_name: &'a str,
+    /// Any text after the command keyword, trimmed.
+    #[allow(dead_code)]
+    pub args: &'a str,
+}
+
+/// Returns the full list of registered bot commands.
+///
+/// Add new commands here — they will automatically appear in `help` output.
+pub fn commands() -> &'static [BotCommand] {
+    &[BotCommand {
+        name: "help",
+        description: "Show this list of available commands",
+        handler: handle_help,
+    }]
+}
+
+/// Try to match a user message against a registered bot command.
+///
+/// The message is expected to be the raw body text from Matrix (e.g.,
+/// `"@timmy help"`). The bot mention prefix is stripped before matching.
+///
+/// Returns `Some(response)` if a command matched, `None` otherwise (the
+/// caller should fall through to the LLM).
+pub fn try_handle_command(
+    bot_name: &str,
+    bot_user_id: &str,
+    message: &str,
+) -> Option<String> {
+    let command_text = strip_bot_mention(message, bot_name, bot_user_id);
+    let trimmed = command_text.trim();
+    if trimmed.is_empty() {
+        return None;
+    }
+
+    let (cmd_name, args) = match trimmed.split_once(char::is_whitespace) {
+        Some((c, a)) => (c, a.trim()),
+        None => (trimmed, ""),
+    };
+    let cmd_lower = cmd_name.to_ascii_lowercase();
+
+    let ctx = CommandContext {
+        bot_name,
+        args,
+    };
+
+    commands()
+        .iter()
+        .find(|c| c.name == cmd_lower)
+        .map(|c| (c.handler)(&ctx))
+}
+
+/// Strip the bot mention prefix from a raw message body.
+///
+/// Handles these forms (case-insensitive where applicable):
+/// - `@bot_localpart:server.com rest` → `rest`
+/// - `@bot_localpart rest` → `rest`
+/// - `DisplayName rest` → `rest`
+fn strip_bot_mention<'a>(message: &'a str, bot_name: &str, bot_user_id: &str) -> &'a str {
+    let trimmed = message.trim();
+
+    // Try full Matrix user ID (e.g. "@timmy:homeserver.local")
+    if let Some(rest) = strip_prefix_ci(trimmed, bot_user_id) {
+        return rest;
+    }
+
+    // Try @localpart (e.g. "@timmy")
+    if let Some(localpart) = bot_user_id.split(':').next()
+        && let Some(rest) = strip_prefix_ci(trimmed, localpart)
+    {
+        return rest;
+    }
+
+    // Try display name (e.g. "Timmy")
+    if let Some(rest) = strip_prefix_ci(trimmed, bot_name) {
+        return rest;
+    }
+
+    trimmed
+}
+
+/// Case-insensitive prefix strip that also requires the match to end at a
+/// word boundary (whitespace, punctuation, or end-of-string).
+fn strip_prefix_ci<'a>(text: &'a str, prefix: &str) -> Option<&'a str> {
+    if text.len() < prefix.len() {
+        return None;
+    }
+    if !text[..prefix.len()].eq_ignore_ascii_case(prefix) {
+        return None;
+    }
+    let rest = &text[prefix.len()..];
+    // Must be at end or followed by non-alphanumeric
+    match rest.chars().next() {
+        None => Some(rest), // exact match, empty remainder
+        Some(c) if c.is_alphanumeric() || c == '-' || c == '_' => None, // not a word boundary
+        _ => Some(rest),
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Built-in command handlers
+// ---------------------------------------------------------------------------
+
+fn handle_help(ctx: &CommandContext) -> String {
+    let mut output = format!("**{} Commands**\n\n", ctx.bot_name);
+    for cmd in commands() {
+        output.push_str(&format!("- **{}** — {}\n", cmd.name, cmd.description));
+    }
+    output
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // -- strip_bot_mention --------------------------------------------------
+
+    #[test]
+    fn strip_mention_full_user_id() {
+        let rest = strip_bot_mention(
+            "@timmy:homeserver.local help",
+            "Timmy",
+            "@timmy:homeserver.local",
+        );
+        assert_eq!(rest.trim(), "help");
+    }
+
+    #[test]
+    fn strip_mention_localpart() {
+        let rest = strip_bot_mention("@timmy help me", "Timmy", "@timmy:homeserver.local");
+        assert_eq!(rest.trim(), "help me");
+    }
+
+    #[test]
+    fn strip_mention_display_name() {
+        let rest = strip_bot_mention("Timmy help", "Timmy", "@timmy:homeserver.local");
+        assert_eq!(rest.trim(), "help");
+    }
+
+    #[test]
+    fn strip_mention_display_name_case_insensitive() {
+        let rest = strip_bot_mention("timmy help", "Timmy", "@timmy:homeserver.local");
+        assert_eq!(rest.trim(), "help");
+    }
+
+    #[test]
+    fn strip_mention_no_match_returns_original() {
+        let rest = strip_bot_mention("hello world", "Timmy", "@timmy:homeserver.local");
+        assert_eq!(rest, "hello world");
+    }
+
+    #[test]
+    fn strip_mention_does_not_match_longer_name() {
+        // "@timmybot" should NOT match "@timmy"
+        let rest = strip_bot_mention("@timmybot help", "Timmy", "@timmy:homeserver.local");
+        assert_eq!(rest, "@timmybot help");
+    }
+
+    #[test]
+    fn strip_mention_comma_after_name() {
+        let rest = strip_bot_mention("@timmy, help", "Timmy", "@timmy:homeserver.local");
+        assert_eq!(rest.trim().trim_start_matches(',').trim(), "help");
+    }
+
+    // -- try_handle_command -------------------------------------------------
+
+    #[test]
+    fn help_command_matches() {
+        let result = try_handle_command("Timmy", "@timmy:homeserver.local", "@timmy help");
+        assert!(result.is_some(), "help command should match");
+    }
+
+    #[test]
+    fn help_command_case_insensitive() {
+        let result = try_handle_command("Timmy", "@timmy:homeserver.local", "@timmy HELP");
+        assert!(result.is_some(), "HELP should match case-insensitively");
+    }
+
+    #[test]
+    fn unknown_command_returns_none() {
+        let result = try_handle_command(
+            "Timmy",
+            "@timmy:homeserver.local",
+            "@timmy what is the weather?",
+        );
+        assert!(result.is_none(), "non-command should return None");
+    }
+
+    #[test]
+    fn help_output_contains_all_commands() {
+        let result = try_handle_command("Timmy", "@timmy:homeserver.local", "@timmy help");
+        let output = result.unwrap();
+        for cmd in commands() {
+            assert!(
+                output.contains(cmd.name),
+                "help output must include command '{}'",
+                cmd.name
+            );
+            assert!(
+                output.contains(cmd.description),
+                "help output must include description for '{}'",
+                cmd.name
+            );
+        }
+    }
+
+    #[test]
+    fn help_output_uses_bot_name() {
+        let result = try_handle_command("HAL", "@hal:example.com", "@hal help");
+        let output = result.unwrap();
+        assert!(
+            output.contains("HAL Commands"),
+            "help output should use bot name: {output}"
+        );
+    }
+
+    #[test]
+    fn help_output_formatted_as_markdown() {
+        let result = try_handle_command("Timmy", "@timmy:homeserver.local", "@timmy help");
+        let output = result.unwrap();
+        assert!(
+            output.contains("**help**"),
+            "command name should be bold: {output}"
+        );
+        assert!(
+            output.contains("- **"),
+            "commands should be in a list: {output}"
+        );
+    }
+
+    #[test]
+    fn empty_message_after_mention_returns_none() {
+        let result = try_handle_command("Timmy", "@timmy:homeserver.local", "@timmy");
+        assert!(
+            result.is_none(),
+            "bare mention with no command should fall through to LLM"
+        );
+    }
+
+    // -- strip_prefix_ci ----------------------------------------------------
+
+    #[test]
+    fn strip_prefix_ci_basic() {
+        assert_eq!(strip_prefix_ci("Hello world", "hello"), Some(" world"));
+    }
+
+    #[test]
+    fn strip_prefix_ci_no_match() {
+        assert_eq!(strip_prefix_ci("goodbye", "hello"), None);
+    }
+
+    #[test]
+    fn strip_prefix_ci_word_boundary_required() {
+        assert_eq!(strip_prefix_ci("helloworld", "hello"), None);
+    }
+
+    #[test]
+    fn strip_prefix_ci_exact_match() {
+        assert_eq!(strip_prefix_ci("hello", "hello"), Some(""));
+    }
+
+    // -- commands registry --------------------------------------------------
+
+    #[test]
+    fn commands_registry_is_not_empty() {
+        assert!(
+            !commands().is_empty(),
+            "command registry must contain at least one command"
+        );
+    }
+
+    #[test]
+    fn all_command_names_are_lowercase() {
+        for cmd in commands() {
+            assert_eq!(
+                cmd.name,
+                cmd.name.to_ascii_lowercase(),
+                "command name '{}' must be lowercase",
+                cmd.name
+            );
+        }
+    }
+
+    #[test]
+    fn all_commands_have_descriptions() {
+        for cmd in commands() {
+            assert!(
+                !cmd.description.is_empty(),
+                "command '{}' must have a description",
+                cmd.name
+            );
+        }
+    }
+}