# 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

# The binary lives in /usr/local/bin, not the working directory: config
# loading searches the working directory, and with a YAML config type Viper
# also matches an extension-less file named "dnswatcher" there, so a binary
# named "dnswatcher" in that directory would be parsed as a config file.
COPY --from=builder /src/bin/dnswatcher /usr/local/bin/dnswatcher

# Run as an unprivileged user. The data directory is owned by that user so
# writes succeed both on a bind mount and when Docker seeds a fresh named
# volume from the image (a fresh volume inherits this directory's ownership).
RUN addgroup -S 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

WORKDIR /var/lib/dnswatcher

USER dnswatcher

EXPOSE 8080

# busybox wget (already in alpine) probes the health endpoint. PORT defaults
# to 8080 and is honoured if the operator overrides it.
HEALTHCHECK --interval=30s --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"]