thermograph/frontend/Dockerfile

# Thermograph frontend: server-rendered content pages, the interactive tool's
# SPA shells, and every static asset. Split from the monorepo (repo-split
# Stage 7), rewritten as a Go service (server/). No migrations, no DB, no
# pre-boot logic -- a plain exec-form CMD is enough (unlike backend, no
# separate entrypoint script needed).
#
# Multi-stage: the golang builder runs vet + the full Go test suite before
# building, so every published image provably passed the hermetic tier with
# the exact toolchain that compiled the shipping binary (this replaces the
# old in-image pytest step in .forgejo/workflows/build.yml -- the runtime
# image carries no toolchain to test with). The final stage is Alpine, not
# distroless: the Swarm stack (infra/deploy/stack/thermograph-stack.yml)
# bind-mounts a bash entrypoint shim (env-entrypoint.sh) over this image's
# entrypoint, so bash must exist inside the container; curl serves the
# HEALTHCHECK, same line as ever.
FROM golang:1.26 AS builder

WORKDIR /src

# Module graph first so the download layer caches across source-only changes.
COPY server/go.mod server/go.sum ./
RUN go mod download

COPY server/ ./

# internal/content's tests read two directories the same three-levels-up
# relative path away from the test file's own package dir (go test always
# runs with cwd set there): the committed golden fixtures (frontend/tests/
# fixtures/*.json — the same set the Python golden-diff comparison used) and
# the SSR copy (frontend/content/*.yaml, content_loader.go's LoadGlossary
# etc.). This stage only copies server/ into /src (so /src has no "frontend/"
# parent to climb to), which is why both land at container-root paths here
# instead — same three-levels-up relationship the tests' relative paths
# expect, just anchored differently.
COPY tests/fixtures /tests/fixtures
COPY content /content

# static/units.js is copied for ONE test: internal/format's
# TestFCountriesMatchesUnitsJS, which asserts the browser's F_REGIONS still
# matches the Go/backend Fahrenheit country set. The builder stage is the only
# place CI ever executes these tests, so without this the check would skip in CI
# and only ever run on a developer's checkout. Same three-levels-up relationship
# the test expects (/src/internal/format -> /static/units.js), anchored the same
# way the two directories above are.
#
# The sibling backend cross-check cannot be wired up this way: the build context
# is frontend/, so backend/ is structurally unreachable and that test stays a
# checkout-only guard.
COPY static/units.js /static/units.js

RUN test -z "$(gofmt -l .)" && go vet ./... && go test ./...

# Static binary: CGO off (no libc dependency on Alpine), -trimpath for
# reproducible paths, -s -w to strip debug info the container never uses.
RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" \
    -o /out/thermograph-frontend .

FROM alpine:3.22

# bash: required by the Swarm stack's env-entrypoint.sh shim (see above).
# curl: the HEALTHCHECK below (pulls in ca-certificates as a dependency).
RUN apk add --no-cache bash curl

# Same uid as the Python image: 10001 is the uid infra provisions readable
# secrets for (deploy-stack.sh installs /etc/thermograph/stack.env
# uid-10001-readable) -- do not change it. Explicit group (Alpine's `adduser
# -S` with no -G falls back to an existing system group, not a same-named
# one -- a bare `--chown=thermograph` below then has no "thermograph" group
# to resolve, which the classic (non-BuildKit) builder rejects outright).
RUN addgroup -S -g 10001 thermograph \
    && adduser -S -u 10001 -G thermograph -h /home/thermograph thermograph

COPY --from=builder /out/thermograph-frontend /usr/local/bin/thermograph-frontend

# The binary embeds its HTML templates (server/internal/render); static/ and
# content/ stay on disk, resolved relative to the working directory (see
# server/internal/config: StaticDir="static", ContentDir="content"), so /app
# mirrors the repo layout the config expects. Read-only at runtime -- the
# service is stateless and holds no data of its own.
#
# Numeric --chown, not the name: needs no /etc/passwd|group lookup at COPY
# time, so it works identically under BuildKit and the classic builder (the
# CI runner installs plain `docker.io`, no buildx plugin, so a build there
# silently uses the classic builder unless BuildKit is forced).
COPY --chown=10001:10001 static/ /app/static/
COPY --chown=10001:10001 content/ /app/content/

USER thermograph
WORKDIR /app

# No WORKERS knob anymore: uvicorn needed a process count, the Go server
# handles concurrency in one process. (The stack/compose files never set it
# for frontend, so nothing references it.)
ENV PORT=8080 \
    THERMOGRAPH_BASE=/

EXPOSE 8080

HEALTHCHECK --interval=30s --timeout=5s --start-period=40s --retries=3 \
    CMD curl -fsS http://127.0.0.1:${PORT}/healthz || exit 1

# Exec form, no shell wrapper: the Swarm shim receives this CMD as $@ and
# execs the binary directly; PID 1 gets SIGTERM and shuts down gracefully.
CMD ["/usr/local/bin/thermograph-frontend"]