#!/bin/bash

# dos2unix mimic script
# Converts DOS/Windows line endings (CRLF) to Unix line endings (LF)

# Function to display usage
usage() {
    echo "Usage: $0 [OPTIONS] FILE..."
    echo "Convert DOS/Windows line endings to Unix line endings"
    echo ""
    echo "Options:"
    echo "  -h, --help     Show this help message"
    echo "  -n, --newfile  Create new file with .unix extension"
    echo "  -b, --backup   Create backup with .bak extension"
    echo "  -q, --quiet    Suppress output messages"
    echo ""
    echo "Examples:"
    echo "  $0 file.txt"
    echo "  $0 -n file.txt"
    echo "  $0 -b file.txt"
    echo "  $0 *.txt"
    exit 1
}

# Function to convert file
convert_file() {
    local input_file="$1"
    local output_file="$2"
    local backup="$3"
    local quiet="$4"
    
    # Check if input file exists
    if [ ! -f "$input_file" ]; then
        echo "Error: File '$input_file' not found" >&2
        return 1
    fi
    
    # Check if file has DOS line endings
    if ! grep -q $'\r' "$input_file"; then
        [ "$quiet" != "true" ] && echo "dos2unix: converting file $input_file to Unix format..."
        [ "$quiet" != "true" ] && echo "dos2unix: $input_file: No conversion needed (already Unix format)"
        return 0
    fi
    
    # Create backup if requested
    if [ "$backup" = "true" ]; then
        if ! cp "$input_file" "${input_file}.bak"; then
            echo "Error: Cannot create backup file" >&2
            return 1
        fi
        [ "$quiet" != "true" ] && echo "dos2unix: created backup: ${input_file}.bak"
    fi
    
    # Convert line endings using sed
    if sed 's/\r$//' "$input_file" > "$output_file"; then
        [ "$quiet" != "true" ] && echo "dos2unix: converting file $input_file to Unix format..."
        
        # If output file is different from input (newfile mode), show message
        if [ "$input_file" != "$output_file" ]; then
            [ "$quiet" != "true" ] && echo "dos2unix: converted to $output_file"
        fi
        
        return 0
    else
        echo "Error: Failed to convert $input_file" >&2
        return 1
    fi
}

# Parse command line arguments
newfile=false
backup=false
quiet=false
files=()

while [[ $# -gt 0 ]]; do
    case $1 in
        -h|--help)
            usage
            ;;
        -n|--newfile)
            newfile=true
            shift
            ;;
        -b|--backup)
            backup=true
            shift
            ;;
        -q|--quiet)
            quiet=true
            shift
            ;;
        -*)
            echo "Error: Unknown option $1" >&2
            usage
            ;;
        *)
            files+=("$1")
            shift
            ;;
    esac
done

# Check if at least one file is provided
if [ ${#files[@]} -eq 0 ]; then
    echo "Error: No files specified" >&2
    usage
fi

# Process each file
exit_code=0
for file in "${files[@]}"; do
    # Expand wildcards
    for expanded_file in $file; do
        if [ -f "$expanded_file" ]; then
            if [ "$newfile" = "true" ]; then
                # Create new file with .unix extension
                output_file="${expanded_file}.unix"
            else
                # Overwrite original file
                output_file="$expanded_file"
            fi
            
            if [ "$newfile" = "true" ]; then
                # For newfile mode, we can directly convert
                convert_file "$expanded_file" "$output_file" "$backup" "$quiet"
            else
                # For in-place conversion, use temporary file
                temp_file=$(mktemp)
                if convert_file "$expanded_file" "$temp_file" "$backup" "$quiet"; then
                    mv "$temp_file" "$expanded_file"
                else
                    rm -f "$temp_file"
                    exit_code=1
                fi
            fi
        else
            echo "Error: File '$expanded_file' not found" >&2
            exit_code=1
        fi
    done
done

exit $exit_code