#!/bin/bash

COVERAGE_THRESHOLD=0.5
PR_COVERAGE_THRESHOLD=80.0
MAIN_COVERAGE_FILE="$1/coverage-summary.json"
RECENT_COVERAGE_FILE="$2/coverage-summary.json"
PR_NUMBER="$3"

if [ ! -f "$MAIN_COVERAGE_FILE" ] || [ ! -f "$RECENT_COVERAGE_FILE" ]; then
    echo "One or both coverage files not found"
    exit 0
fi

COMMENT_BODY="### Coverage Comparison Report
<relative-time datetime=\"$(date -u +"%Y-%m-%dT%H:%M:%SZ")\">Generated on $(date '+%B %d, %Y at %H:%M:%S UTC')</relative-time>

\`\`\`
+-----------------+------------+------------+-----------+
| Metric          | Main       | This PR    | Diff      |
+-----------------+------------+------------+-----------+"

HAS_DECREASE=0
BELOW_THRESHOLD=0

# Calculate average total coverage since the summary doesn't provide an overall total
main_total=0
pr_total=0
metric_count=0

for metric in lines statements branches functions; do
    main=$(jq ".total.${metric}.pct" "$MAIN_COVERAGE_FILE")
    pr=$(jq ".total.${metric}.pct" "$RECENT_COVERAGE_FILE")
    diff=$(echo "$pr - $main" | bc)
    
    main_total=$(echo "$main_total + $main" | bc)
    pr_total=$(echo "$pr_total + $pr" | bc)
    metric_count=$((metric_count + 1))
    
    row=$(printf "| %-15s | %9.2f%% | %9.2f%% | %8.2f%% |" "${metric^}" "$main" "$pr" "$diff")
    COMMENT_BODY+=$'\n'"$row"
    
    if (( $(echo "$diff < -$COVERAGE_THRESHOLD" | bc -l) )); then
        # Write error messages to stderr instead of stdout, since we don't want them to be shown in the PR comment
        echo "::error::${metric^} coverage has decreased by more than ${COVERAGE_THRESHOLD}% ($diff%)" >&2
        HAS_DECREASE=1
    fi
done

COMMENT_BODY+=$'\n'"+-----------------+------------+------------+-----------+"

main_avg=$(echo "scale=2; $main_total / $metric_count" | bc)
pr_avg=$(echo "scale=2; $pr_total / $metric_count" | bc)
total_diff=$(echo "$pr_avg - $main_avg" | bc)

if (( $(echo "$pr_avg < $PR_COVERAGE_THRESHOLD" | bc -l) )); then
    echo "::error::Total coverage ($pr_avg%) is below the minimum required coverage of ${PR_COVERAGE_THRESHOLD}%" >&2
    BELOW_THRESHOLD=1
    HAS_DECREASE=1
fi

row=$(printf "| %-15s | %9.2f%% | %9.2f%% | %8.2f%% |" "Total" "$main_avg" "$pr_avg" "$total_diff")
COMMENT_BODY+=$'\n'"$row"

COMMENT_BODY+=$'\n'"+-----------------+------------+------------+-----------+
\`\`\`"

if [ "$BELOW_THRESHOLD" -eq 1 ]; then
    COMMENT_BODY+=$'\n\n'"🚨 **Error:** Total coverage ($pr_avg%) is below the minimum required coverage of ${PR_COVERAGE_THRESHOLD}%"
elif [ "$HAS_DECREASE" -eq 1 ]; then
    COMMENT_BODY+=$'\n\n'"⚠️ **Warning:** One or more coverage metrics have decreased by more than ${COVERAGE_THRESHOLD}%"
fi

echo "$COMMENT_BODY"
echo "status=$BELOW_THRESHOLD" >> $GITHUB_OUTPUT