# Exercise 12a — Build a Containerfile step by step
#
# Start with an empty Containerfile and add one instruction at a time.
# After each step: podman build -t myapp:latest .
# Then inspect the result before moving on.

cd listings/exercises/ex12a-containerfile-steps/

# -----------------------------------------------------------------------
# Step 1 — Base image
# -----------------------------------------------------------------------
# Containerfile:
#   FROM debian:12

podman build -t myapp:latest .
podman images myapp:latest          # ~121 MB

# -----------------------------------------------------------------------
# Step 2 — Install software (creates a new layer)
# -----------------------------------------------------------------------
# Add to Containerfile:
#   RUN apt-get update && apt-get install -y curl

podman build -t myapp:latest .
podman images myapp:latest          # ~159 MB — layer is visible

# -----------------------------------------------------------------------
# Step 3 — Working directory
# -----------------------------------------------------------------------
# Add to Containerfile:
#   WORKDIR /app

podman build -t myapp:latest .
podman run --rm myapp:latest pwd    # prints /app

# -----------------------------------------------------------------------
# Step 4 — Copy your script into the image
# -----------------------------------------------------------------------
# Add to Containerfile:
#   COPY hello.sh .
#   RUN chmod +x hello.sh

podman build -t myapp:latest .
podman run --rm myapp:latest ls -la # hello.sh is there

# -----------------------------------------------------------------------
# Step 5 — Environment variable
# -----------------------------------------------------------------------
# Add to Containerfile:
#   ENV NAME=Trainee

podman build -t myapp:latest .
podman run --rm myapp:latest env | grep NAME

# -----------------------------------------------------------------------
# Step 6 — Start command
# -----------------------------------------------------------------------
# Add to Containerfile:
#   CMD ["./hello.sh"]

podman build -t myapp:latest .
podman run --rm myapp:latest                 # uses ENV NAME=Trainee
podman run --rm -e NAME=Frank myapp:latest   # override at runtime

# -----------------------------------------------------------------------
# Bonus: layers — chained vs. separate RUN
# -----------------------------------------------------------------------
# Two separate RUN = two layers:
#   RUN apt-get update
#   RUN apt-get install -y curl
#
# One chained RUN = one layer:
#   RUN apt-get update && apt-get install -y curl

podman inspect myapp:latest --format '{{len .RootFS.Layers}} layers'