# syntax=docker/dockerfile:1.7
# Cross-platform build workflow — produces 6 static binaries under ./bin/
#
# Usage:
#   docker build -f docker/Dockerfile.cross --output ./bin .
#
# Or via Makefile:
#   make cross-build

ARG GO_VERSION=1.25
ARG ALPINE_VERSION=3.23

FROM golang:${GO_VERSION}-alpine${ALPINE_VERSION} AS builder

# git  — needed by go mod download for VCS-stamped modules
# ca-certificates — needed for HTTPS during module download
RUN apk add --no-cache ca-certificates git

WORKDIR /workspace

# Cache dependency downloads separately from source
COPY go.mod go.sum ./
RUN go mod download

COPY . .

# Build matrix: GOOS × GOARCH
# CGO_ENABLED=0 ensures fully static, portable binaries (no libc dependency).
# -trimpath removes local path info; -s -w strips debug info for smaller output.
ARG BUILD_FLAGS="-trimpath -ldflags=-s -w"

RUN set -e; \
    mkdir -p /out; \
    for GOOS in linux darwin windows; do \
      for GOARCH in amd64 arm64; do \
        EXT=""; \
        [ "$GOOS" = "windows" ] && EXT=".exe"; \
        OUTPUT="/out/wavelet_${GOOS}_${GOARCH}${EXT}"; \
        echo "==> Building ${OUTPUT}..."; \
        CGO_ENABLED=0 GOOS=${GOOS} GOARCH=${GOARCH} \
          go build \
            -trimpath \
            -ldflags="-s -w" \
            -o "${OUTPUT}" \
            ./main.go; \
      done; \
    done

# ── Export stage ─────────────────────────────────────────────────────────────
# `docker build --output ./bin .` will copy everything from /out into the host.
FROM scratch AS export
COPY --from=builder /out/ /