#
# mal (Make a Lisp) environment definition
#

if test -z $(__mal_env_included__) {
setglobal __mal_env_included = 'true'

source $[dirname $0]/types.sh

# Any environment is a hash_map with an __outer__ key that refers to
# a parent environment (or nil)
proc ENV {
    setglobal r = ''
    _hash_map
    var env = $(r)
    if [[ "${1}" ]] {
        setglobal outer = $(1); shift
        _assoc! $(env) "__outer__" $(outer)
    } else {
        _assoc! $(env) "__outer__" $(__nil)
    }
    setglobal r = $(env)

    if [[ "${1}" && "${@}" ]] {
        var binds = '('${ANON["${1}"]}); shift
        var idx = '0' {
            var fp = $(ANON["${binds["${idx}"]}"])
            if [[ "${fp}" == "&" ]] {
                set idx = $shExpr(' idx + 1 ')
                set fp = $(ANON["${binds["${idx}"]}"])
                _list $(@)
                _assoc! $(env) $(fp) $(r)
                break
            } else {
                _assoc! $(env) $(fp) $(1)
                shift
                set idx = $shExpr(' idx + 1 ')
            }
        }
    }
    setglobal r = $(env)
}

# Find the environment with the key set and return the environment
proc ENV_FIND {
    if _contains? $(1) $(ANON["${2}"]) {
        setglobal r = $(1)
    } else {
        var obj = $(ANON["${1}"])
        eval local outer="\${$(obj)["__outer__"]}"
        if [[ "${outer}" && "${outer}" != "${__nil}" ]] {
            ENV_FIND $(outer) $(2)
        } else {
            setglobal r = ''
        }
    }
}

# Find the environment with the key set and return the value of the
# key in that environment. If no environment contains the key then
# return an error
proc ENV_GET {
    ENV_FIND $(1) $(2)
    var env = $(r)
    var key = $(ANON["${2}"])
    if [[ "${r}" ]] {
        var obj = $(ANON["${env}"])
        eval r="\${$(obj)["$(key)"]}"
    } else {
        _error "'$(key)' not found"
    }
}

proc ENV_SET {
    var key = $(ANON["${2}"])
    _assoc! $(1) $(key) $(3)
}

}