# Lint stage - fast feedback on lint issues, before the build starts.
# The linter is invoked directly rather than through `make lint`: that
# target shells out to `docker build -f Dockerfile.lint`, and there is
# no docker daemon inside a docker build.
# golangci/golangci-lint:v2.12.2 (Debian-based), 2026-08-10
FROM golangci/golangci-lint:v2.12.2@sha256:5cceeef04e53efe1470638d4b4b4f5ceefd574955ab3941b2d9a68a8c9ad5240 AS lint

WORKDIR /src
COPY go.mod go.sum ./
RUN go mod download

COPY . .

RUN make fmt-check
RUN golangci-lint run --config .golangci.yml ./...

# Build stage
# golang 1.25-alpine, 2026-02-28
FROM golang@sha256:f6751d823c26342f9506c03797d2527668d095b0a15f1862cddb4d927a7a4ced AS builder

RUN apk add --no-cache git make gcc musl-dev binutils-gold

# Force BuildKit to run the lint stage before proceeding
COPY --from=lint /src/go.sum /dev/null

WORKDIR /src
COPY go.mod go.sum ./
RUN go mod download

COPY . .

# Run the tests - build fails if any test fails
RUN make test

# Build the binary
RUN make build

# Runtime stage
# alpine 3.21, 2026-02-28
FROM alpine@sha256:c3f8e73fdb79deaebaa2037150150191b9dcbfba68b4a46d70103204c53f4709

RUN apk add --no-cache ca-certificates tzdata

COPY --from=builder /src/bin/dnswatcher /usr/local/bin/dnswatcher

# Run as an unprivileged user that owns the data directory. A fresh named
# volume inherits this ownership; a bind-mounted host directory must be
# owned by uid 10001 (see "Running under upaas" in README.md), or startup
# fails.
RUN addgroup -S -g 10001 dnswatcher \
    && adduser -S -G dnswatcher -u 10001 dnswatcher \
    && mkdir -p /var/lib/dnswatcher \
    && chown dnswatcher:dnswatcher /var/lib/dnswatcher

ENV DNSWATCHER_DATA_DIR=/var/lib/dnswatcher

# Config loading also reads a `.env` file and a file named `dnswatcher`
# (any config extension, or none) from the working directory. `/` holds
# neither, so every setting comes from the environment. Do not make the
# data directory, or the binary's directory, the working directory.
WORKDIR /

USER dnswatcher

EXPOSE 8080

# busybox wget (already in alpine) probes the health endpoint every 10
# seconds, so the container is healthy well before upaas reads its health
# 60 seconds after a deploy and fails the deploy unless it is healthy.
HEALTHCHECK --interval=10s --timeout=5s --start-period=10s --retries=3 \
    CMD wget -q -O /dev/null "http://127.0.0.1:${PORT:-8080}/.well-known/healthcheck" || exit 1

ENTRYPOINT ["/usr/local/bin/dnswatcher"]