1 files changed, 76 insertions, 0 deletions
diff --git a/src/FundLab.Api/NavSeriesProbe.fs b/src/FundLab.Api/NavSeriesProbe.fs
new file mode 100644
index 0000000..7c7a437
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+++ b/src/FundLab.Api/NavSeriesProbe.fs
@@ -0,0 +1,76 @@
+namespace FundLab.Api
+
+open System
+open System.Collections.Concurrent
+open System.Globalization
+open System.Threading
+
+/// One point of a fund's real net-value series.
+type NavSeriesPoint =
+    {
+        NavDate: DateOnly
+        Nav: decimal
+        AccumulatedNav: decimal option
+    }
+
+/// Read-only probe that returns the most recent NAV points for a fund code.
+/// Like INavDateProbe there is no synthetic fallback: a failure is surfaced as a
+/// MarketDataFailure so the API answers 503 with the underlying reason.
+type INavSeriesProbe =
+    abstract RecentNavSeries: code: string * limit: int * CancellationToken -> Result<NavSeriesPoint list, MarketDataFailure>
+
+/// AKShare-backed series probe. Successful lookups are memoised per code and
+/// calendar day (the F# equivalent of functools cache keyed on code + today), so
+/// the UI can re-read the curve during one day without re-spawning the collector.
+/// Failures are never cached.
+type AkshareNavSeriesProbe(collector: IMarketDataCollector) =
+    let cache = ConcurrentDictionary<string, NavSeriesPoint list>(StringComparer.Ordinal)
+
+    let isFundCode (value: string) =
+        not (String.IsNullOrWhiteSpace value)
+        && value.Length = 6
+        && value |> Seq.forall Char.IsDigit
+
+    let clip limit =
+        if limit < 1 then 1
+        elif limit > 250 then 250
+        else limit
+
+    let todayText () =
+        (ConfirmationPolicy.eventDateFor DateTimeOffset.UtcNow).ToString("yyyy-MM-dd", CultureInfo.InvariantCulture)
+
+    member _.Clear() = cache.Clear()
+
+    interface INavSeriesProbe with
+        member _.RecentNavSeries(code, limit, token) =
+            let normalized = if isNull code then "" else code.Trim()
+
+            if not (isFundCode normalized) then
+                Error(InvalidMarketDataRequest "fund code must contain exactly six digits")
+            else
+                let bounded = clip limit
+                let cacheKey = sprintf "%s|%s" normalized (todayText ())
+
+                match cache.TryGetValue cacheKey with
+                | true, cached -> Ok(cached |> List.truncate bounded)
+                | _ ->
+                    match collector.FetchNav(normalized, token) with
+                    | Error message -> Error(MarketDataCollectorUnavailable message)
+                    | Ok json ->
+                        match MarketData.parseNavPayload json with
+                        | Error message -> Error(InvalidMarketDataPayload message)
+                        | Ok payload ->
+                            let points =
+                                payload.Observations
+                                |> List.filter (fun observation -> observation.Nav > 0m)
+                                |> List.map (fun observation ->
+                                    {
+                                        NavDate = observation.NavDate
+                                        Nav = observation.Nav
+                                        AccumulatedNav = observation.AccumulatedNav
+                                    })
+                                |> List.distinctBy (fun point -> point.NavDate)
+                                |> List.sortByDescending (fun point -> point.NavDate)
+
+                            cache.[cacheKey] <- points
+                            Ok(points |> List.truncate bounded)