Add selectable declared-param columns to LogPreview (ticket 015)

Extend GET /api/logs to derive each declared param's value per log line
(regex + capture group + kind, matching that line's text) and include it as
a params map on LogEntryDto, omitting entries that don't match rather than
sending nulls. Add GET /api/params (list_params, mirroring list_metrics) so
the frontend can discover currently-declared param names. In LogPreview, add
a column-picker popover backed by that list, with the selection persisted in
localStorage under `ottyl.logPreview.visibleParamColumns`.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

src/api.rs

@@ -102,7 +102,7 @@ pub fn router(
         .route("/api/logs", get(get_logs))
         .route("/api/timeline", get(get_timeline))
         .route("/api/stats", get(get_stats))
-        .route("/api/params", post(declare_param))
+        .route("/api/params", get(list_params).post(declare_param))
         .route("/api/metrics", get(list_metrics).post(declare_metric))
         .route("/api/metrics/{name}", get(get_metric_bucket_values))
         .route("/api/settings/css", get(list_css).post(import_css))
@@ -152,6 +152,18 @@ async fn get_stats(State(state): State<ApiState>) -> impl IntoResponse {
     }
 }
 
+/// `GET /api/params` — lists all declared params (name, regex, capture
+/// group, kind) as `Vec<ParamDeclarationDto>`. Mirrors `list_metrics` below
+/// (ticket 015 needed this for LogPreview's column picker; ticket 004 only
+/// exposed the equivalent for metrics).
+async fn list_params(State(state): State<ApiState>) -> impl IntoResponse {
+    match ask(&state.engine, EngineQuery::ParamDeclarations).await {
+        Ok(EngineResponse::ParamDeclarations(declarations)) => Json(declarations).into_response(),
+        Ok(_) => StatusCode::INTERNAL_SERVER_ERROR.into_response(),
+        Err(status) => status.into_response(),
+    }
+}
+
 /// `POST /api/params` — declares a param. Body mirrors `DeclareParamRequest`:
 /// `{ "name": "...", "message_match_regex": "...", "capture_group": "...",
 /// "kind": "string" | "number" | "timestamp" }`. On success, also persists

src/dto.rs

@@ -9,6 +9,13 @@ pub struct LogEntryDto {
     pub sequence: u64,
     pub timestamp_ms: i64,
     pub text: String,
+    /// Derived param values (ticket 001's `ParamDeclaration`s) for this line,
+    /// keyed by param name. Only params whose regex actually matched this
+    /// line's text (and whose captured group parsed as the declared `kind`)
+    /// are present — a non-matching param is omitted rather than sent as
+    /// null, so the frontend can render a blank/dash for anything missing
+    /// from the map.
+    pub params: BTreeMap<String, MetricPrimitive>,
 }
 
 #[derive(Debug, Clone, Serialize)]

src/engine.rs

@@ -364,6 +364,49 @@ fn param_declarations_range(
         })
 }
 
+/// Compiles every currently-declared param's regex once, so `derive_log_params`
+/// can be applied to many lines without recompiling each param's regex per
+/// line. A param whose stored regex somehow fails to compile (shouldn't
+/// happen — `declare_param` validates it before storing) is skipped rather
+/// than panicking.
+fn compiled_param_declarations(
+    index: &BTreeMap<IndexKey, DataValue>,
+) -> Vec<(String, Regex, String, MetricPrimitiveKind)> {
+    param_declarations_range(index)
+        .filter_map(|(name, message_match_regex, capture_group, kind)| {
+            Regex::new(message_match_regex)
+                .ok()
+                .map(|re| (name.to_string(), re, capture_group.to_string(), kind))
+        })
+        .collect()
+}
+
+/// Runs every declared param's regex against one log line's text, returning
+/// the derived `MetricPrimitive` values keyed by param name. A param is
+/// omitted from the result (rather than included as null/empty) when its
+/// regex doesn't match the line, its capture group doesn't match, or the
+/// captured text fails to parse as the param's declared `kind` — see
+/// `LogEntryDto::params`.
+fn derive_log_params(
+    text: &str,
+    declarations: &[(String, Regex, String, MetricPrimitiveKind)],
+) -> BTreeMap<String, MetricPrimitive> {
+    let mut params = BTreeMap::new();
+    for (name, regex, capture_group, kind) in declarations {
+        let Some(captures) = regex.captures(text) else {
+            continue;
+        };
+        let Some(raw) = captures.name(capture_group) else {
+            continue;
+        };
+        let Some(value) = parse_metric_primitive(raw.as_str(), *kind) else {
+            continue;
+        };
+        params.insert(name.clone(), value);
+    }
+    params
+}
+
 fn logs_range(index: &BTreeMap<IndexKey, DataValue>) -> impl Iterator<Item = (u64, Timestamp, &str)> {
     index.range(IndexKey::Start..IndexKey::LogParamSplit).filter_map(|(key, value)| {
         match (key, value) {
@@ -379,6 +422,17 @@ fn handle_query(index: &BTreeMap<IndexKey, DataValue>, query: EngineQuery) -> En
     match query {
         EngineQuery::Logs(params) => {
             let limit = params.limit.unwrap_or(500).min(10_000);
+            // Compile each currently-declared param's regex once up front, then
+            // apply the compiled set to every *returned* line below (ticket 015).
+            // Perf note: this is a straightforward per-returned-line,
+            // per-declared-param regex scan — O(lines_returned * declared_params)
+            // — rather than precomputing/caching derived params for the whole log
+            // range. That's fine at this codebase's current scale (v1), but if
+            // either the log volume or number of declared params grows a lot,
+            // this should move to incremental derivation at ingest time (mirroring
+            // how `apply_all_metrics` already does for metric buckets) instead of
+            // recomputing on every `/api/logs` query.
+            let compiled_params = compiled_param_declarations(index);
             let entries: Vec<LogEntryDto> = logs_range(index)
                 .filter(|(sequence, timestamp, _)| {
                     params.since_sequence.is_none_or(|since| *sequence > since)
@@ -390,6 +444,7 @@ fn handle_query(index: &BTreeMap<IndexKey, DataValue>, query: EngineQuery) -> En
                     sequence,
                     timestamp_ms: timestamp.as_millis(),
                     text: text.to_string(),
+                    params: derive_log_params(text, &compiled_params),
                 })
                 .collect();
             EngineResponse::Logs(entries)
@@ -835,4 +890,30 @@ mod tests {
         assert_eq!(bucket_values(&index, "requests", None).count(), 1);
         assert_eq!(bucket_values(&index, "durations", None).count(), 1);
     }
+
+    #[test]
+    fn logs_query_includes_declared_params_on_matching_lines_only() {
+        let mut index = BTreeMap::new();
+        declare_param(&mut index, request("level", r"level=(?P<level>\w+)", "level")).unwrap();
+        ingest_log(&mut index, 0, "level=info hello");
+        ingest_log(&mut index, 1, "no match here");
+
+        let EngineResponse::Logs(entries) =
+            handle_query(&index, EngineQuery::Logs(LogsParams {
+                since_sequence: None,
+                start_ms: None,
+                end_ms: None,
+                limit: None,
+            }))
+        else {
+            panic!("expected Logs response");
+        };
+
+        assert_eq!(entries.len(), 2);
+        assert_eq!(
+            entries[0].params.get("level"),
+            Some(&MetricPrimitive::String("info".to_string()))
+        );
+        assert!(entries[1].params.get("level").is_none());
+    }
 }

webapp/src/components/LogPreview.tsx

@@ -1,13 +1,145 @@
-import type { LogEntry } from '../lib/api'
+import { useEffect, useRef, useState } from 'react'
+import {
+  fetchParamDeclarations,
+  metricPrimitiveToDisplayString,
+  type LogEntry,
+} from '../lib/api'
+
+/// localStorage key for LogPreview's selected param columns. Namespaced
+/// under `ottyl.` since this is the app's first localStorage usage — kept
+/// distinct enough that future per-viewer preferences elsewhere in the app
+/// won't collide with it.
+const VISIBLE_PARAM_COLUMNS_STORAGE_KEY = 'ottyl.logPreview.visibleParamColumns'
+
+function loadVisibleParamColumns(): string[] {
+  try {
+    const raw = localStorage.getItem(VISIBLE_PARAM_COLUMNS_STORAGE_KEY)
+    if (!raw) return []
+    const parsed = JSON.parse(raw)
+    return Array.isArray(parsed) ? parsed.filter((v): v is string => typeof v === 'string') : []
+  } catch {
+    return []
+  }
+}
+
+function saveVisibleParamColumns(columns: string[]) {
+  try {
+    localStorage.setItem(VISIBLE_PARAM_COLUMNS_STORAGE_KEY, JSON.stringify(columns))
+  } catch {
+    // best-effort — a private browsing mode or full storage just means the
+    // selection won't persist across reloads.
+  }
+}
+
+function ColumnPicker({
+  paramNames,
+  visible,
+  onToggle,
+}: {
+  paramNames: string[]
+  visible: Set<string>
+  onToggle: (name: string) => void
+}) {
+  const [open, setOpen] = useState(false)
+  const ref = useRef<HTMLDivElement>(null)
+
+  useEffect(() => {
+    if (!open) return
+    function onClickOutside(e: MouseEvent) {
+      if (ref.current && !ref.current.contains(e.target as Node)) setOpen(false)
+    }
+    document.addEventListener('mousedown', onClickOutside)
+    return () => document.removeEventListener('mousedown', onClickOutside)
+  }, [open])
+
+  return (
+    <div ref={ref} className="relative">
+      <button
+        type="button"
+        onClick={() => setOpen((v) => !v)}
+        className="rounded border border-neutral-700 px-2 py-1 text-xs text-neutral-300 hover:bg-neutral-800"
+      >
+        Columns{visible.size > 0 ? ` (${visible.size})` : ''}
+      </button>
+      {open && (
+        <div className="absolute right-0 z-10 mt-1 w-56 rounded border border-neutral-700 bg-neutral-950 p-2 shadow-lg">
+          {paramNames.length === 0 ? (
+            <div className="px-1 py-1 text-xs text-neutral-500">No declared params yet.</div>
+          ) : (
+            <ul className="flex max-h-64 flex-col gap-1 overflow-auto">
+              {paramNames.map((name) => (
+                <li key={name}>
+                  <label className="flex cursor-pointer items-center gap-2 rounded px-1 py-0.5 text-xs text-neutral-200 hover:bg-neutral-900">
+                    <input
+                      type="checkbox"
+                      checked={visible.has(name)}
+                      onChange={() => onToggle(name)}
+                      className="accent-neutral-400"
+                    />
+                    {name}
+                  </label>
+                </li>
+              ))}
+            </ul>
+          )}
+        </div>
+      )}
+    </div>
+  )
+}
 
 export function LogPreview({ logs }: { logs: LogEntry[] }) {
+  const [paramNames, setParamNames] = useState<string[]>([])
+  const [visibleParamColumns, setVisibleParamColumns] = useState<string[]>(loadVisibleParamColumns)
+
+  useEffect(() => {
+    let cancelled = false
+    fetchParamDeclarations()
+      .then((declarations) => {
+        if (!cancelled) setParamNames(declarations.map((d) => d.name))
+      })
+      .catch(() => {
+        // params API not reachable yet; column picker just stays empty until
+        // the next successful fetch.
+      })
+    return () => {
+      cancelled = true
+    }
+  }, [])
+
+  const visible = new Set(visibleParamColumns)
+
+  function toggleColumn(name: string) {
+    setVisibleParamColumns((current) => {
+      const next = current.includes(name)
+        ? current.filter((c) => c !== name)
+        : [...current, name]
+      saveVisibleParamColumns(next)
+      return next
+    })
+  }
+
+  // Only render columns for params that are both selected and still known to
+  // exist, so a stale localStorage entry for a since-removed param doesn't
+  // leave a dangling column.
+  const columns = visibleParamColumns.filter((name) => paramNames.includes(name))
+
   return (
+    <div className="flex flex-1 flex-col overflow-hidden">
+      <div className="flex justify-end border-b border-neutral-900 px-3 py-1">
+        <ColumnPicker paramNames={paramNames} visible={visible} onToggle={toggleColumn} />
+      </div>
       <div className="flex-1 overflow-auto">
         <table className="w-full border-collapse text-left text-xs">
           <thead className="sticky top-0 bg-neutral-950 text-neutral-500">
             <tr>
               <th className="w-16 px-3 py-1 font-normal">Seq</th>
               <th className="w-40 px-3 py-1 font-normal">Timestamp</th>
+              {columns.map((name) => (
+                <th key={name} className="w-32 px-3 py-1 font-normal">
+                  {name}
+                </th>
+              ))}
               <th className="px-3 py-1 font-normal">Message</th>
             </tr>
           </thead>
@@ -18,12 +150,20 @@ export function LogPreview({ logs }: { logs: LogEntry[] }) {
                 <td className="whitespace-nowrap px-3 py-1 text-neutral-500">
                   {new Date(log.timestamp_ms).toLocaleTimeString()}
                 </td>
+                {columns.map((name) => {
+                  const value = log.params[name]
+                  return (
+                    <td key={name} className="whitespace-nowrap px-3 py-1 text-neutral-400">
+                      {value ? metricPrimitiveToDisplayString(value) : '—'}
+                    </td>
+                  )
+                })}
                 <td className="px-3 py-1 text-neutral-200">{log.text}</td>
               </tr>
             ))}
             {logs.length === 0 && (
               <tr>
-              <td colSpan={3} className="px-3 py-6 text-center text-neutral-600">
+                <td colSpan={3 + columns.length} className="px-3 py-6 text-center text-neutral-600">
                   No logs yet — pipe something into ottyl.
                 </td>
               </tr>
@@ -31,5 +171,6 @@ export function LogPreview({ logs }: { logs: LogEntry[] }) {
           </tbody>
         </table>
       </div>
+    </div>
   )
 }

webapp/src/lib/api.ts

@@ -1,7 +1,33 @@
+/// `MetricPrimitive` is a Rust enum with derived `Serialize`, so its JSON
+/// form is externally tagged, e.g. `{ "String": "info" }`, `{ "Number":
+/// { "Int": 5 } }`, `{ "Timestamp": 1710000000000 }`.
+export type MetricPrimitive =
+  | { String: string }
+  | { Number: { Int: number } | { Float: number } }
+  | { Timestamp: number }
+
+export function metricPrimitiveToDisplayString(value: MetricPrimitive): string {
+  if ('String' in value) return value.String
+  if ('Timestamp' in value) return String(value.Timestamp)
+  if ('Int' in value.Number) return String(value.Number.Int)
+  return String(value.Number.Float)
+}
+
 export interface LogEntry {
   sequence: number
   timestamp_ms: number
   text: string
+  /// Derived param values (declared via `POST /api/params`) that matched
+  /// this line's text, keyed by param name. A param with no match on this
+  /// line is simply absent from the map.
+  params: Record<string, MetricPrimitive>
+}
+
+export interface ParamDeclaration {
+  name: string
+  message_match_regex: string
+  capture_group: string
+  kind: 'string' | 'number' | 'timestamp'
 }
 
 export interface TimelineBucket {
@@ -54,3 +80,7 @@ export function fetchTimeline(params: {
 export function fetchStats(): Promise<Stats> {
   return getJson('/api/stats')
 }
+
+export function fetchParamDeclarations(): Promise<ParamDeclaration[]> {
+  return getJson('/api/params')
+}