#!/usr/bin/env bash
set -euo pipefail

if [[ $# -ne 1 ]]; then
    echo "Usage: $0 <eval-name>"
    echo "Example: $0 opencode-glm47"
    exit 1
fi

EVAL_NAME="eval/$1"
EVAL_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"

# Verify we're on main
CURRENT_BRANCH=$(git branch --show-current)
if [[ "${CURRENT_BRANCH}" != "main" ]]; then
    echo "Error: Must be on 'main' branch to start an evaluation."
    echo "Current branch: ${CURRENT_BRANCH}"
    exit 1
fi

# Check if eval branch already exists
if git show-ref --verify --quiet refs/heads/"${EVAL_NAME}"; then
    echo "Error: Evaluation branch '${EVAL_NAME}' already exists."
    echo "Use a different name or delete the existing branch first."
    exit 1
fi

echo "Creating evaluation branch: ${EVAL_NAME}"

# Create orphan branch
git switch --orphan "${EVAL_NAME}"

# Copy only flake files from main
git checkout main -- flake.nix flake.lock .envrc SPEC.md

# Initial commit
git add .
git commit -m "Initial: setup evaluation environment"

# Set up direnv
direnv allow

echo ""
echo "Evaluation environment ready!"
echo "Working on branch: ${EVAL_NAME}"
echo ""
echo "Run 'git checkout main' when you're done to return to main."