From 89cdeb09679299e97840ca5061c9a431973b0a66 Mon Sep 17 00:00:00 2001
From: Ryan Malloy <ryan@supported.systems>
Date: Mon, 23 Feb 2026 19:46:29 -0700
Subject: [PATCH] Fix HTML chart output path for nobody container user

Use MCNOAA_CHARTS_DIR env var (defaults to artifacts/charts/ for
local dev) so the container's nobody user can write HTML charts
to /tmp/charts instead of the read-only /app working directory.
---
 Dockerfile.mcp                   |  1 +
 src/mcnoaa_tides/tools/charts.py | 12 ++++++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/Dockerfile.mcp b/Dockerfile.mcp
index 5ca7746..f499316 100644
--- a/Dockerfile.mcp
+++ b/Dockerfile.mcp
@@ -15,6 +15,7 @@ WORKDIR /app
 ENV UV_COMPILE_BYTECODE=1
 ENV PATH="/app/.venv/bin:$PATH"
 ENV MPLCONFIGDIR=/tmp/matplotlib
+ENV MCNOAA_CHARTS_DIR=/tmp/charts
 
 COPY --from=deps /app/.venv /app/.venv
 COPY src/ src/
diff --git a/src/mcnoaa_tides/tools/charts.py b/src/mcnoaa_tides/tools/charts.py
index b5775aa..3dbb5da 100644
--- a/src/mcnoaa_tides/tools/charts.py
+++ b/src/mcnoaa_tides/tools/charts.py
@@ -189,9 +189,17 @@ def register(mcp: FastMCP) -> None:
 
 
 def _save_html(html: str, station_id: str, chart_type: str) -> Path:
-    """Save HTML chart to artifacts/charts/ and return the path."""
+    """Save HTML chart and return the path.
+
+    Uses $MCNOAA_CHARTS_DIR if set, otherwise falls back to
+    artifacts/charts/ (relative to cwd).  The container sets
+    MCNOAA_CHARTS_DIR=/tmp/charts so the nobody user can write.
+    """
+    import os
+
     timestamp = datetime.now(timezone.utc).strftime("%Y%m%d_%H%M%S")
-    out_dir = Path("artifacts/charts")
+    base = os.environ.get("MCNOAA_CHARTS_DIR", "artifacts/charts")
+    out_dir = Path(base)
     out_dir.mkdir(parents=True, exist_ok=True)
     path = out_dir / f"{station_id}_{chart_type}_{timestamp}.html"
     path.write_text(html, encoding="utf-8")