dedup the snapshot loading function

src/commands/history.zig

@@ -180,29 +180,25 @@ fn runPortfolio(
     color: bool,
     out: *std.Io.Writer,
 ) !void {
-    // Derive history/ from the portfolio path's directory.
-    const portfolio_dir = std.fs.path.dirname(portfolio_path) orelse ".";
-    const history_dir = try std.fs.path.join(allocator, &.{ portfolio_dir, "history" });
-    defer allocator.free(history_dir);
-
-    var loaded = try history_io.loadHistoryDir(allocator, history_dir);
-    defer loaded.deinit();
+    // Derive history/ + load snapshots + build series in one shot.
+    // Both --rebuild-rollup (wants raw snapshots) and the main render
+    // path (wants the series) share this, so the combined loader gives
+    // us both without re-parsing.
+    var tl = try history_io.loadTimeline(allocator, portfolio_path);
+    defer tl.deinit();
 
     if (opts.rebuild_rollup) {
-        try rebuildRollup(allocator, history_dir, loaded.snapshots, out);
+        try rebuildRollup(allocator, tl.history_dir, tl.loaded.snapshots, out);
         return;
     }
 
-    if (loaded.snapshots.len == 0) {
-        try out.print("No portfolio snapshots found in {s}.\n", .{history_dir});
+    if (tl.loaded.snapshots.len == 0) {
+        try out.print("No portfolio snapshots found in {s}.\n", .{tl.history_dir});
         try out.print("Run `zfin snapshot` to capture the first one.\n", .{});
         return;
     }
 
-    const series = try timeline.buildSeries(allocator, loaded.snapshots);
-    defer series.deinit();
-
-    const filtered = try timeline.filterByDate(allocator, series.points, opts.since, opts.until);
+    const filtered = try timeline.filterByDate(allocator, tl.series.points, opts.since, opts.until);
     defer allocator.free(filtered);
 
     if (filtered.len == 0) {

src/history.zig

@@ -26,6 +26,7 @@ const std = @import("std");
 const srf = @import("srf");
 const snapshot_mod = @import("models/snapshot.zig");
 const Date = @import("models/date.zig").Date;
+const timeline = @import("analytics/timeline.zig");
 
 pub const Error = error{
     /// The file didn't open a `#!srfv1` directive or couldn't be
@@ -207,6 +208,73 @@ pub fn loadHistoryDir(
     };
 }
 
+/// Derive `<dirname(portfolio_path)>/history` and return the joined
+/// path (caller-owned). Thin helper, but exposed so CLI and TUI agree
+/// on the convention (history/ is always a sibling of portfolio.srf).
+pub fn deriveHistoryDir(
+    allocator: std.mem.Allocator,
+    portfolio_path: []const u8,
+) ![]u8 {
+    const portfolio_dir = std.fs.path.dirname(portfolio_path) orelse ".";
+    return std.fs.path.join(allocator, &.{ portfolio_dir, "history" });
+}
+
+/// Result of `loadTimeline` — bundles the raw snapshot collection and
+/// the derived timeline series so callers can reach either without
+/// re-parsing.
+///
+/// `series.points` is sorted ascending by date; `loaded.snapshots` is
+/// in filesystem enumeration order. Both are kept alive together —
+/// `series.points` references dates that live inside `loaded`'s
+/// snapshot rows, and the callers may want `loaded.snapshots` directly
+/// for non-timeline uses (e.g. rollup building).
+pub const LoadedTimeline = struct {
+    loaded: LoadedHistory,
+    series: timeline.TimelineSeries,
+    /// Directory we loaded from, caller-owned. Carried through for
+    /// callers that want to print diagnostics or locate sibling files
+    /// (rollup.srf, etc.).
+    history_dir: []u8,
+    allocator: std.mem.Allocator,
+
+    pub fn deinit(self: *LoadedTimeline) void {
+        self.series.deinit();
+        self.loaded.deinit();
+        self.allocator.free(self.history_dir);
+    }
+};
+
+/// End-to-end snapshot timeline loader: derives history/, reads every
+/// `*-portfolio.srf` file, and builds the sorted timeline series. The
+/// single entry point used by both the CLI `zfin history` command and
+/// the TUI history tab — their earlier copies had subtle divergences
+/// (different dir-split logic, slightly different empty-state ordering)
+/// that a shared helper rules out.
+///
+/// Returns `loaded.snapshots.len == 0` on an empty history dir rather
+/// than erroring; callers check and produce their own "no snapshots"
+/// message. Parse failures on individual files are logged to stderr by
+/// `loadHistoryDir` and the offending file is skipped.
+pub fn loadTimeline(
+    allocator: std.mem.Allocator,
+    portfolio_path: []const u8,
+) !LoadedTimeline {
+    const history_dir = try deriveHistoryDir(allocator, portfolio_path);
+    errdefer allocator.free(history_dir);
+
+    var loaded = try loadHistoryDir(allocator, history_dir);
+    errdefer loaded.deinit();
+
+    const series = try timeline.buildSeries(allocator, loaded.snapshots);
+
+    return .{
+        .loaded = loaded,
+        .series = series,
+        .history_dir = history_dir,
+        .allocator = allocator,
+    };
+}
+
 // ── Tests ────────────────────────────────────────────────────
 
 const testing = std.testing;

src/tui.zig

@@ -377,9 +377,11 @@ pub const App = struct {
     // History tab state
     history_loaded: bool = false,
     history_disabled: bool = false, // true when no portfolio path (history requires it)
-    history_load_result: ?history_io.LoadedHistory = null,
-    history_series: ?timeline_mod.TimelineSeries = null,
-    history_metric: timeline_mod.Metric = .net_worth,
+    history_timeline: ?history_io.LoadedTimeline = null,
+    // Default to `.liquid` — that's the metric most worth watching
+    // day-to-day. Illiquid barely changes, net_worth is dominated by
+    // liquid anyway, so "show me liquid" is the headline view.
+    history_metric: timeline_mod.Metric = .liquid,
 
     // Mouse wheel debounce for cursor-based tabs (portfolio, options).
     // Terminals often send multiple wheel events per physical tick.

src/tui/history_tab.zig

@@ -41,49 +41,27 @@ pub fn loadData(app: *App) void {
         return;
     };
 
-    const dir_end = if (std.mem.lastIndexOfScalar(u8, portfolio_path, std.fs.path.sep)) |idx| idx else {
-        app.setStatus("Cannot derive history/ from portfolio path");
-        return;
-    };
-    const portfolio_dir = portfolio_path[0..dir_end];
-
-    const history_dir = std.fs.path.join(app.allocator, &.{ portfolio_dir, "history" }) catch return;
-    defer app.allocator.free(history_dir);
-
-    var loaded = history_io.loadHistoryDir(app.allocator, history_dir) catch {
+    // Shared path with the `zfin history` CLI command — derives
+    // history/, loads every snapshot, and builds the timeline series.
+    // If history/ is missing or all files are malformed, we surface a
+    // status message and leave `app.history_timeline` null; the
+    // renderer handles the empty case.
+    app.history_timeline = history_io.loadTimeline(app.allocator, portfolio_path) catch {
         app.setStatus("Failed to read history/ directory");
         return;
     };
-    errdefer loaded.deinit();
 
-    if (loaded.snapshots.len == 0) {
-        loaded.deinit();
+    if (app.history_timeline.?.loaded.snapshots.len == 0) {
+        freeLoaded(app);
         app.setStatus("No snapshots in history/ (run: zfin snapshot)");
-        return;
     }
-
-    var series = timeline.buildSeries(app.allocator, loaded.snapshots) catch {
-        loaded.deinit();
-        app.setStatus("Failed to build timeline series");
-        return;
-    };
-
-    // Commit
-    app.history_load_result = loaded;
-    app.history_series = series;
-    _ = &series; // keep mutable reference (not needed once committed)
 }
 
-/// Free both the snapshot bytes and the timeline series. Caller must
-/// null out the fields after this if they want to allow re-loading.
+/// Release the loaded timeline (if any).
 pub fn freeLoaded(app: *App) void {
-    if (app.history_series) |s| {
-        s.deinit();
-        app.history_series = null;
-    }
-    if (app.history_load_result) |*lh| {
-        lh.deinit();
-        app.history_load_result = null;
+    if (app.history_timeline) |*tl| {
+        tl.deinit();
+        app.history_timeline = null;
     }
 }
 
@@ -99,7 +77,8 @@ pub fn cycleMetric(app: *App) void {
 // ── Rendering ─────────────────────────────────────────────────
 
 pub fn buildStyledLines(app: *App, arena: std.mem.Allocator) ![]const StyledLine {
-    return renderHistoryLines(arena, app.theme, app.history_series, app.history_metric);
+    const series: ?timeline.TimelineSeries = if (app.history_timeline) |tl| tl.series else null;
+    return renderHistoryLines(arena, app.theme, series, app.history_metric);
 }
 
 /// Pure renderer — no App dependency. Builds the styled lines from a
@@ -177,13 +156,17 @@ pub fn renderHistoryLines(
         .style = th.mutedStyle(),
     });
 
-    // Show up to max_table_rows most recent, but preserve oldest-first
-    // ordering for deltas to accumulate intuitively.
+    // Show up to max_table_rows most recent. Render newest-first so
+    // the latest snapshot sits directly under the column headers,
+    // matching typical "recent items" lists and saving the eye a scroll.
     const start = if (points.len > max_table_rows) points.len - max_table_rows else 0;
     const first = points[0]; // deltas still measured from series start
 
-    for (points[start..]) |p| {
-        const text = try fmtTableRow(arena, p, first);
+    const window = points[start..];
+    var i: usize = window.len;
+    while (i > 0) {
+        i -= 1;
+        const text = try fmtTableRow(arena, window[i], first);
         try lines.append(arena, .{ .text = text, .style = th.contentStyle() });
     }