#!/usr/bin/env bash
# update-license-headers.sh - Update MIT license headers in .cs files
#
# Usage:
#   ./scripts/update-license-headers.sh [options]
#
# This script updates all .cs files to use consistent license headers:
#   - Replaces "Eli Pinkerton" with "wallstop"
#   - Corrects copyright years based on git creation date
#   - Adds standard two-line header to files missing it
#
# Options:
#   --dry-run    Show what would be changed without modifying files
#   --verbose    Show all files processed, not just changes
#   --help       Show this help message
#
# Standard header format:
#   // MIT License - Copyright (c) <year> wallstop
#   // Full license text: https://github.com/wallstop/unity-helpers/blob/main/LICENSE

set -euo pipefail

# Configuration
REPO_START_YEAR=2023
CURRENT_YEAR=2026
COPYRIGHT_HOLDER="wallstop"
LICENSE_URL="https://github.com/wallstop/unity-helpers/blob/main/LICENSE"

# Parse arguments
DRY_RUN=false
VERBOSE=false
for arg in "$@"; do
    case "$arg" in
        --dry-run)
            DRY_RUN=true
            ;;
        --verbose)
            VERBOSE=true
            ;;
        --help|-h)
            head -21 "$0" | tail -19
            exit 0
            ;;
        *)
            echo "Unknown option: $arg" >&2
            exit 1
            ;;
    esac
done

# Get script directory and repo root
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"

cd "$REPO_ROOT"

# Counters
total_files=0
updated_files=0
added_header_files=0
skipped_files=0

# Check if file has standard MIT header (first line contains MIT License)
has_mit_header() {
    local file="$1"
    local first_line
    first_line=$(head -1 "$file" 2>/dev/null || echo "")
    [[ "$first_line" == *"MIT License"* ]]
}

# Check if file has the license URL line
has_license_url() {
    local file="$1"
    local second_line
    second_line=$(sed -n '2p' "$file" 2>/dev/null || echo "")
    [[ "$second_line" == *"Full license text:"* ]]
}

# Get git creation year for a file
get_git_creation_year() {
    local file="$1"
    local year

    # Use --follow to track across renames, --diff-filter=A for additions only
    year=$(git log --follow --diff-filter=A --format=%ad --date=format:%Y -- "$file" 2>/dev/null | tail -1)

    if [[ -z "$year" ]]; then
        # No git history - use current year
        echo "$CURRENT_YEAR"
    elif [[ "$year" -lt "$REPO_START_YEAR" ]]; then
        # Pre-repo - use repo start year
        echo "$REPO_START_YEAR"
    else
        echo "$year"
    fi
}

# Extract current year from header
get_header_year() {
    local file="$1"
    local first_line
    first_line=$(head -1 "$file" 2>/dev/null || echo "")

    if [[ "$first_line" =~ Copyright\ \(c\)\ ([0-9]{4}) ]]; then
        echo "${BASH_REMATCH[1]}"
    else
        echo ""
    fi
}

# Update a file with correct header
update_file() {
    local file="$1"
    local target_year="$2"
    local rel_path="${file#$REPO_ROOT/}"

    local header_line1="// MIT License - Copyright (c) $target_year $COPYRIGHT_HOLDER"
    local header_line2="// Full license text: $LICENSE_URL"

    if has_mit_header "$file"; then
        # File has MIT header - update it
        local current_year
        current_year=$(get_header_year "$file")
        local first_line
        first_line=$(head -1 "$file")

        local needs_update=false
        local changes=""

        # Check if we need to update the first line
        if [[ "$first_line" == *"Eli Pinkerton"* ]] || [[ "$current_year" != "$target_year" ]]; then
            needs_update=true
            if [[ "$first_line" == *"Eli Pinkerton"* ]]; then
                changes="${changes}holder "
            fi
            if [[ "$current_year" != "$target_year" ]]; then
                changes="${changes}year($current_year->$target_year) "
            fi
        fi

        # Check if we need to add the second line
        if ! has_license_url "$file"; then
            needs_update=true
            changes="${changes}add_url "
        fi

        if [[ "$needs_update" == true ]]; then
            ((updated_files++)) || true
            echo "UPDATE: $rel_path [${changes% }]"

            if [[ "$DRY_RUN" == false ]]; then
                local temp_file
                temp_file=$(mktemp)

                # Write new header
                echo "$header_line1" > "$temp_file"

                # Check if second line exists and is license URL
                if has_license_url "$file"; then
                    # Keep existing second line format (update if needed)
                    echo "$header_line2" >> "$temp_file"
                    # Skip first two lines of original
                    tail -n +3 "$file" >> "$temp_file"
                else
                    # Add license URL line
                    echo "$header_line2" >> "$temp_file"
                    # Skip only first line of original
                    tail -n +2 "$file" >> "$temp_file"
                fi

                mv "$temp_file" "$file"
            fi
        elif [[ "$VERBOSE" == true ]]; then
            echo "OK: $rel_path"
        fi
    else
        # File lacks MIT header - add it
        ((added_header_files++)) || true
        echo "ADD HEADER: $rel_path [year=$target_year]"

        if [[ "$DRY_RUN" == false ]]; then
            local temp_file
            temp_file=$(mktemp)

            echo "$header_line1" > "$temp_file"
            echo "$header_line2" >> "$temp_file"
            echo "" >> "$temp_file"
            cat "$file" >> "$temp_file"

            mv "$temp_file" "$file"
        fi
    fi
}

# Print mode
if [[ "$DRY_RUN" == true ]]; then
    echo "=== DRY RUN MODE - No files will be modified ==="
    echo ""
fi

echo "Updating license headers..."
echo "Copyright holder: $COPYRIGHT_HOLDER"
echo "License URL: $LICENSE_URL"
echo ""

# Find all .cs files
while IFS= read -r -d '' file; do
    ((total_files++)) || true

    # Determine target year
    target_year=$(get_git_creation_year "$file")

    # Update the file
    update_file "$file" "$target_year"

done < <(find "$REPO_ROOT" -name "*.cs" -type f -print0 | sort -z)

# Print summary
echo ""
echo "=== License Header Update Summary ==="
echo "Total .cs files:     $total_files"
echo "Updated headers:     $updated_files"
echo "Added headers:       $added_header_files"
echo "Unchanged:           $((total_files - updated_files - added_header_files))"

if [[ "$DRY_RUN" == true ]]; then
    echo ""
    echo "This was a dry run. Run without --dry-run to apply changes."
fi