storkit: merge 413_refactor_split_slack_rs_into_focused_modules

server/src/chat/transport/slack/format.rs

@@ -0,0 +1,128 @@
+//! Markdown to Slack mrkdwn conversion.
+
+/// Convert Markdown text to Slack mrkdwn format.
+///
+/// Slack uses its own "mrkdwn" syntax which differs from standard Markdown.
+/// This function converts common Markdown constructs so messages render
+/// nicely in Slack instead of showing raw Markdown syntax.
+pub fn markdown_to_slack(text: &str) -> String {
+    use regex::Regex;
+    use std::sync::LazyLock;
+
+    // Regexes are compiled once and reused across calls.
+    static RE_FENCED_BLOCK: LazyLock<Regex> =
+        LazyLock::new(|| Regex::new(r"(?ms)^```.*?\n(.*?)^```").unwrap());
+    static RE_HEADER: LazyLock<Regex> =
+        LazyLock::new(|| Regex::new(r"(?m)^#{1,6}\s+(.+)$").unwrap());
+    static RE_BOLD_ITALIC: LazyLock<Regex> =
+        LazyLock::new(|| Regex::new(r"\*\*\*(.+?)\*\*\*").unwrap());
+    static RE_BOLD: LazyLock<Regex> =
+        LazyLock::new(|| Regex::new(r"\*\*(.+?)\*\*").unwrap());
+    static RE_STRIKETHROUGH: LazyLock<Regex> =
+        LazyLock::new(|| Regex::new(r"~~(.+?)~~").unwrap());
+    static RE_LINK: LazyLock<Regex> =
+        LazyLock::new(|| Regex::new(r"\[([^\]]+)\]\(([^)]+)\)").unwrap());
+
+    // 1. Protect fenced code blocks by replacing them with placeholders.
+    let mut code_blocks: Vec<String> = Vec::new();
+    let protected = RE_FENCED_BLOCK.replace_all(text, |caps: &regex::Captures| {
+        let idx = code_blocks.len();
+        code_blocks.push(caps[0].to_string());
+        format!("\x00CODEBLOCK{idx}\x00")
+    });
+    let mut out = protected.into_owned();
+
+    // 2. Headers → bold text.
+    out = RE_HEADER.replace_all(&out, "*$1*").into_owned();
+
+    // 3. Bold+italic (***text***) → bold italic (*_text_*).
+    out = RE_BOLD_ITALIC.replace_all(&out, "*_${1}_*").into_owned();
+
+    // 4. Bold (**text**) → Slack bold (*text*).
+    out = RE_BOLD.replace_all(&out, "*$1*").into_owned();
+
+    // 5. Strikethrough (~~text~~) → Slack strikethrough (~text~).
+    out = RE_STRIKETHROUGH.replace_all(&out, "~$1~").into_owned();
+
+    // 6. Links [text](url) → Slack mrkdwn format <url|text>.
+    out = RE_LINK.replace_all(&out, "<$2|$1>").into_owned();
+
+    // 7. Restore code blocks.
+    for (idx, block) in code_blocks.iter().enumerate() {
+        out = out.replace(&format!("\x00CODEBLOCK{idx}\x00"), block);
+    }
+
+    out
+}
+
+// ── Tests ───────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn slack_headers_become_bold() {
+        assert_eq!(markdown_to_slack("# Title"), "*Title*");
+        assert_eq!(markdown_to_slack("## Subtitle"), "*Subtitle*");
+        assert_eq!(markdown_to_slack("### Section"), "*Section*");
+        assert_eq!(markdown_to_slack("###### Deep"), "*Deep*");
+    }
+
+    #[test]
+    fn slack_bold_converted() {
+        assert_eq!(markdown_to_slack("**bold text**"), "*bold text*");
+    }
+
+    #[test]
+    fn slack_bold_italic_converted() {
+        assert_eq!(markdown_to_slack("***emphasis***"), "*_emphasis_*");
+    }
+
+    #[test]
+    fn slack_strikethrough_converted() {
+        assert_eq!(markdown_to_slack("~~removed~~"), "~removed~");
+    }
+
+    #[test]
+    fn slack_links_converted_to_mrkdwn() {
+        assert_eq!(
+            markdown_to_slack("[click here](https://example.com)"),
+            "<https://example.com|click here>"
+        );
+    }
+
+    #[test]
+    fn slack_inline_code_preserved() {
+        assert_eq!(markdown_to_slack("use `foo()` here"), "use `foo()` here");
+    }
+
+    #[test]
+    fn slack_fenced_code_block_preserved() {
+        let input = "```rust\nlet x = 1;\n```";
+        let output = markdown_to_slack(input);
+        assert!(output.contains("let x = 1;"), "code block content must be preserved");
+        assert!(output.contains("```"), "fenced code delimiters must be preserved");
+    }
+
+    #[test]
+    fn slack_code_block_content_not_transformed() {
+        let input = "```\n**not bold** # not header\n```";
+        let output = markdown_to_slack(input);
+        assert!(
+            output.contains("**not bold**"),
+            "markdown inside code blocks must not be transformed"
+        );
+    }
+
+    #[test]
+    fn slack_plain_text_unchanged() {
+        let plain = "Hello, this is a plain message with no formatting.";
+        assert_eq!(markdown_to_slack(plain), plain);
+    }
+
+    #[test]
+    fn slack_empty_string_unchanged() {
+        assert_eq!(markdown_to_slack(""), "");
+    }
+}