#!/bin/bash

# update_copyright.sh
# Updates copyright year ranges in a source file based on git history
#
# Usage: ./update_copyright.sh [--dry-run] <file>
#
# Examples:
#   # Update a single file
#   ./update_copyright.sh src/main.cpp
#
#   # Dry-run on a single file
#   ./update_copyright.sh --dry-run src/main.cpp
#
#   # Update all C++ files using find -exec
#   find src \( -name "*.cpp" -o -name "*.hpp" \) -exec ./update_copyright.sh {} \;
#
#   # Dry-run on all C++ files
#   find src \( -name "*.cpp" -o -name "*.hpp" \) -exec ./update_copyright.sh --dry-run {} \;

set -e

# Check for dry-run flag
DRY_RUN=false
FILE=""

if [ "$1" = "--dry-run" ]; then
    DRY_RUN=true
    FILE="$2"
elif [ "$1" = "--help" ] || [ "$1" = "-h" ]; then
    grep "^#" "$0" | sed 's/^# \?//'
    exit 0
else
    FILE="$1"
fi

# Check if file argument provided
if [ -z "$FILE" ]; then
    echo "Error: No file specified"
    echo "Usage: $0 [--dry-run] <file>"
    echo "Run '$0 --help' for more information"
    exit 1
fi

# Check if file exists
if [ ! -f "$FILE" ]; then
    echo "Error: File not found: $FILE"
    exit 1
fi

# Get the repository root
REPO_ROOT=$(git rev-parse --show-toplevel)
cd "$REPO_ROOT"

# Copyright holder name
COPYRIGHT_HOLDER="Moritz Martinius"

# Function to get first and last commit years for a file
get_years_for_file() {
    local file="$1"

    # Get the year of the first commit that touched this file
    first_year=$(git log --follow --format=%ad --date=format:%Y --reverse "$file" 2>/dev/null | head -1)

    # Get the year of the last commit that touched this file
    last_year=$(git log --follow --format=%ad --date=format:%Y -1 "$file" 2>/dev/null)

    # If file is not in git, use current year
    if [ -z "$first_year" ]; then
        first_year=$(date +%Y)
        last_year=$(date +%Y)
    fi

    echo "$first_year $last_year"
}

# Get years from git history
read -r first_year last_year <<< "$(get_years_for_file "$FILE")"

# Determine the copyright year string
if [ "$first_year" = "$last_year" ]; then
    year_string="$first_year"
else
    year_string="$first_year-$last_year"
fi

# Check if file has a copyright notice
if ! grep -q "Copyright (C)" "$FILE"; then
    echo "No copyright notice found in $FILE, skipping"
    exit 0
fi

if [ "$DRY_RUN" = true ]; then
    # Just show what would be changed
    current_year=$(grep "Copyright (C)" "$FILE" | sed -n 's/.*Copyright (C) \([0-9]\{4\}\(-[0-9]\{4\}\)\?\).*/\1/p' | head -1)
    if [ "$current_year" != "$year_string" ]; then
        echo "Would update $FILE: $current_year → $year_string"
    else
        echo "No change needed for $FILE (already $year_string)"
    fi
else
    # Update the copyright line
    # Matches patterns like "Copyright (C) 2023 Moritz Martinius" or "Copyright (C) 2023-2024 Moritz Martinius"
    # Handle variable whitespace between year and name

    # Get current year from file for comparison
    current_year=$(grep "Copyright (C)" "$FILE" | sed -n 's/.*Copyright (C) \([0-9]\{4\}\(-[0-9]\{4\}\)\?\).*/\1/p' | head -1)

    if [ "$current_year" = "$year_string" ]; then
        echo "No changes needed for $FILE (already $year_string)"
    else
        sed -i "s/Copyright (C) [0-9]\{4\}\(-[0-9]\{4\}\)\? \+$COPYRIGHT_HOLDER/Copyright (C) $year_string  $COPYRIGHT_HOLDER/" "$FILE"
        echo "✓ Updated $FILE: $current_year → $year_string"
    fi
fi