path_manager

# Manage ':' separated variables, such as PATH, LD_LIBRARY_PATH

# Check whether a path exists in a var
_contains_path() {
    local var_value=":$1:"
    local target=":$2:"
    # `$target` is quoted, so glob characters in it are matched literally
    [[ "$var_value" == *"$target"* ]]
}

# Append a path to a path variable
# Example:
#   path_var_append PATH /usr/local/bin
path_var_append() {
    if [[ $# -ne 2 ]]; then
        echo "Usage: ${FUNCNAME[0]} VARIABLE_NAME PATH" >&2
        return 1
    fi
    local var_name="$1"
    local new_path="$2"
    local current_value
    eval "current_value=\${$var_name}"

    if ! _contains_path "$current_value" "$new_path"; then
        if [[ -z "$current_value" ]]; then
            export "$var_name=$new_path"
        else
            export "$var_name=$current_value:$new_path"
        fi
    fi
}

# Prepend a path to a path variable
# Example:
#   path_var_prepend PATH /usr/local/bin
path_var_prepend() {
    if [[ $# -ne 2 ]]; then
        echo "Usage: ${FUNCNAME[0]} VARIABLE_NAME PATH" >&2
        return 1
    fi
    local var_name="$1"
    local new_path="$2"
    local current_value
    eval "current_value=\${$var_name}"

    if ! _contains_path "$current_value" "$new_path"; then
        if [[ -z "$current_value" ]]; then
            export "$var_name=$new_path"
        else
            export "$var_name=$new_path:$current_value"
        fi
    fi
}

# Remove a path from path variable
# Example:
#   path_var_remove PATH /usr/local/bin
path_var_remove() {
    if [[ $# -ne 2 ]]; then
        echo "Usage: ${FUNCNAME[0]} VARIABLE_NAME PATH" >&2
        return 1
    fi
    local var_name="$1"
    local remove_path="$2"
    local current_value
    eval "current_value=\${$var_name}"

    local result=":"
    local parts
    # zsh uses `-A` for arrays; bash uses `-a`
    if [[ -n "$ZSH_VERSION" ]]; then
        IFS=':' read -rA parts <<< "$current_value"
    else
        IFS=':' read -ra parts <<< "$current_value"
    fi
    for part in "${parts[@]}"; do
        [[ "$part" != "$remove_path" && -n "$part" ]] && result+="$part:"
    done

    result="${result#:}"
    result="${result%:}"
    export "$var_name=$result"
}