ui: trend panel + range selector on host repo page

internal/server/http/ui_repo.go

@@ -1,9 +1,12 @@
 package http
 
 import (
+	"context"
 	"encoding/json"
 	"errors"
+	"html/template"
 	"log/slog"
+	"math"
 	stdhttp "net/http"
 	"strconv"
 	"strings"
@@ -13,6 +16,7 @@ import (
 
 	"gitea.dcglab.co.uk/steve/restic-manager/internal/server/ui"
 	"gitea.dcglab.co.uk/steve/restic-manager/internal/store"
+	"gitea.dcglab.co.uk/steve/restic-manager/internal/web/sparkline"
 )
 
 // ui_repo.go — HTML form-driven repo-tab handlers (connection,
@@ -27,6 +31,15 @@ import (
 //   POST /hosts/{id}/admin-credentials               — admin (prune) creds
 //   POST /hosts/{id}/admin-credentials/delete        — clear admin creds
 
+// repoTrendView is the data the repo_size_chart partial needs.
+// HostID + Range round-trip through the htmx range pills; ChartSVG
+// is pre-rendered server-side so the partial is just a wrapper.
+type repoTrendView struct {
+	HostID   string
+	Range    string
+	ChartSVG template.HTML
+}
+
 // repoStatsView is a flat, pre-dereferenced projection of
 // store.HostRepoStats for use in templates. Nil pointer fields are
 // collapsed to zero/false and accompanied by a Has* sentinel so the
@@ -74,6 +87,10 @@ type hostRepoPage struct {
 	// Nil when no row exists yet (fresh hosts).
 	StatsView *repoStatsView
 
+	// Trend holds the pre-rendered chart fragment data for the
+	// 30/90/365-day repo-size + snapshot-count overlay chart.
+	Trend repoTrendView
+
 	// Snapshots-by-tag — map[group_name]count, plus an "untagged" row.
 	SnapshotsByTag    map[string]int
 	UntaggedSnapshots int
@@ -225,9 +242,52 @@ func (s *Server) loadHostRepoPage(r *stdhttp.Request, host store.Host) (*hostRep
 			}
 		}
 	}
+	p.Trend = s.buildRepoTrendView(r.Context(), host.ID, "30d")
+
 	return p, nil
 }
 
+// buildRepoTrendView builds the chart-partial data for a host. Used
+// both by the page-load (initial 30d render) and the htmx fragment
+// endpoint (range switching). An invalid rangeKey falls back to "30d".
+func (s *Server) buildRepoTrendView(ctx context.Context, hostID, rangeKey string) repoTrendView {
+	days := 30
+	switch rangeKey {
+	case "90d":
+		days = 90
+	case "1y":
+		days = 365
+	default:
+		rangeKey = "30d"
+	}
+	since := time.Now().UTC().AddDate(0, 0, -days)
+	pts, err := s.deps.Store.ListHostRepoStatsHistory(ctx, hostID, since)
+	if err != nil {
+		slog.Warn("ui repo trend: list history", "host_id", hostID, "err", err)
+	}
+	sizes := make([]float64, len(pts))
+	counts := make([]float64, len(pts))
+	dayList := make([]time.Time, len(pts))
+	for i, p := range pts {
+		dayList[i] = p.Day
+		if p.TotalSizeBytes == nil {
+			sizes[i] = math.NaN()
+		} else {
+			sizes[i] = float64(*p.TotalSizeBytes)
+		}
+		if p.SnapshotCount == nil {
+			counts[i] = math.NaN()
+		} else {
+			counts[i] = float64(*p.SnapshotCount)
+		}
+	}
+	chartSVG := sparkline.RenderChart([]sparkline.Series{
+		{Name: "size", Stroke: "#3b82f6", Axis: sparkline.AxisLeft, Format: sparkline.FormatBytes, Points: sizes},
+		{Name: "snapshots", Stroke: "#f59e0b", Axis: sparkline.AxisRight, Format: sparkline.FormatCount, Points: counts},
+	}, dayList, sparkline.ChartOpts{Width: 600, Height: 220})
+	return repoTrendView{HostID: hostID, Range: rangeKey, ChartSVG: chartSVG}
+}
+
 func (s *Server) handleUIHostRepo(w stdhttp.ResponseWriter, r *stdhttp.Request) {
 	u := s.requireUIUser(w, r)
 	if u == nil {