FROM golang:1.25 AS gomail-builder
ARG TARGETARCH=amd64
ARG TARGETOS=linux
WORKDIR /gomail
RUN { \
    echo 'package main'; \
    echo ''; \
    echo 'import ('; \
    echo '    "flag"'; \
    echo '    "fmt"'; \
    echo '    "io"'; \
    echo '    "net/smtp"'; \
    echo '    "os"'; \
    echo ')'; \
    echo ''; \
    echo 'func main() {'; \
    echo '    from := flag.String("f", "minitor@localhost", "envelope sender")'; \
    echo '    flag.Parse()'; \
    echo '    recipients := flag.Args()'; \
    echo ''; \
    echo '    if len(recipients) == 0 {'; \
    echo '        fmt.Fprintln(os.Stderr, "usage: sendmail [-f sender] recipient...")'; \
    echo '        os.Exit(1)'; \
    echo '    }'; \
    echo ''; \
    echo '    body, err := io.ReadAll(os.Stdin)'; \
    echo '    if err != nil {'; \
    echo '        fmt.Fprintln(os.Stderr, err)'; \
    echo '        os.Exit(1)'; \
    echo '    }'; \
    echo ''; \
    echo '    relay := os.Getenv("SMTP_RELAY")'; \
    echo '    if relay == "" {'; \
    echo '        relay = "172.17.0.2"'; \
    echo '    }'; \
    echo ''; \
    echo '    port := os.Getenv("SMTP_PORT")'; \
    echo '    if port == "" {'; \
    echo '        port = "25"'; \
    echo '    }'; \
    echo ''; \
    echo '    sender := os.Getenv("SMTP_SENDER")'; \
    echo '    if sender == "" {'; \
    echo '        sender = *from'; \
    echo '    }'; \
    echo ''; \
    echo '    debug := os.Getenv("DEBUG") != ""'; \
    echo '    if debug {'; \
    echo '        fmt.Fprintln(os.Stderr, fmt.Sprintf("[sendmail] relay=%s port=%s sender=%s recipients=%v", relay, port, sender, recipients))'; \
    echo '        fmt.Fprintln(os.Stderr, "[sendmail] body:")'; \
    echo '        fmt.Fprintln(os.Stderr, string(body))'; \
    echo '    }'; \
    echo ''; \
    echo '    if err = smtp.SendMail(relay+":"+port, nil, sender, recipients, body); err != nil {'; \
    echo '        fmt.Fprintln(os.Stderr, err)'; \
    echo '        os.Exit(1)'; \
    echo '    }'; \
    echo '    if debug {'; \
    echo '        fmt.Fprintln(os.Stderr, "[sendmail] sent successfully")'; \
    echo '    }'; \
    echo '}'; \
    } > main.go
RUN go mod init gomail && \
    CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -o /usr/local/bin/sendmail .


FROM golang:1.25 AS builder
WORKDIR /app
COPY ./go.mod ./go.sum /app/
RUN go mod download
COPY ./*.go /app/
RUN rm -f /app/gomail.go

ARG TARGETARCH=amd64
ARG TARGETOS=linux
ARG VERSION=dev
RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags "-X main.version=${VERSION}" -a -installsuffix nocgo -o minitor .

FROM alpine:3.23
RUN mkdir /app
WORKDIR /app/

# Copy minitor in
COPY --from=builder /app/minitor .

# Copy sendmail (gomail) in
COPY --from=gomail-builder /usr/local/bin/sendmail /usr/local/bin/sendmail

# Add common checking tools
# hadolint ignore=DL3018
RUN apk --no-cache add bash=~5 curl=~8 jq=~1 bind-tools=~9 tzdata

# Add minitor user for running as non-root
RUN addgroup -S minitor && adduser -S minitor -G minitor

# Copy scripts
COPY ./scripts /app/scripts
COPY default_config.hcl /app/config.hcl
RUN chmod -R 755 /app/scripts

# Drop to non-root user
USER minitor

ENTRYPOINT [ "./minitor" ]