single meta class

1 files changed, 152 insertions, 0 deletions

diff --git a/bos-meta-class.sh b/bos-meta-class.sh
new file mode 100644
index 0000000..4d701b5
--- /dev/null
+++ b/bos-meta-class.sh
@@ -0,0 +1,152 @@
+#!bash
+
+# this encoding must match bos-namespaces/encode-into
+bos_5fbos_2fmeta_2fclass_5fmeta="bos-dipatch/invoke bos/meta/class 0"
+declare -a bos_5fbos_2fmeta_2fclass_5fmro=( "bos/meta/class" )
+
+# these are instance methods of the base metaclass
+
+function bos/meta/class/isa-for-into() {
+    bos-namespaces/store-array-for-into "$1" isa "$2"
+}
+
+function bos/meta/class/set-superclasses-for() {
+    local isa_name; $self isa-for-into isa_name "$1"
+    local -n isa="$isa_name"
+    shift
+
+    isa=( "$@" )
+
+    return 0
+}
+
+function bos/meta/class/get-superclasses-for-into() {
+    local -n dest="$1"
+    local isa_name; $self isa-for-into isa_name "$2"
+    local -n isa="$isa_name"
+
+    dest=( "${isa[@]}" )
+
+    return 0
+}
+
+function bos/meta/class/mro-for-into() {
+    bos-namespaces/store-array-for-into "$1" mro "$2"
+}
+
+# given a class and an array, sets the array to the list of clasess to
+# look into when resolving a method call for the given class, in order
+function bos/meta/class/make-mro-for() {
+    local class="$1"
+    local mro_name; $self mro-for-into mro_name "$class"
+    local -n mro="$mro_name"
+
+    # TODO: use C3 and support multiple inheritance
+
+    mro=( "$class" )
+    local -a nextclasses
+    $self get-superclasses-for-into nextclasses "$class"
+
+    while [[ "${#nextclasses}" -gt 0 ]]; do
+        mro+=( "${nextclasses[0]}" )
+        class="${nextclasses[0]}"
+        $self get-superclasses-for-into nextclasses "$class"
+    done
+
+    return 0
+}
+
+# find the first class (in MRO) that defines a given method
+function bos/meta/class/find-method-into() {
+    local -n bos_meta_class_find_method_result="$1"
+    # the class that started the method dispatch (the class of $self,
+    # usually)
+    local class="$2"
+    # what class invoked next/method (if we're doing next/method)
+    local start_from_class="$3"
+    # the method to look for
+    local method="$4"
+
+    local mro_store; $self mro-for-into mro_store "$class"
+    local -n mro="$mro_store"
+
+    # minimal MRO: the class itself
+    if [[ "${#mro[@]}" -eq 0 ]]; then
+        mro=( "$class" )
+    fi
+
+    local idx=0
+
+    # if we don't have a $start_from_class, it means we're doing the
+    # initial method resolution, so don't skip any class in $mro
+    if [[ -n "$start_from_class" ]]; then
+        for (( ; idx < "${#mro[@]}" ; ++idx )); do
+            if [[ "${mro[$idx]}" == "$start_from_class" ]]; then
+                (( ++idx ))
+                break
+            fi
+        done
+    fi
+
+    for (( ; idx < "${#mro[@]}" ; ++idx )); do
+        local full_name="${mro[$idx]}/${method}"
+        if declare -F "$full_name" >/dev/null; then
+            bos_meta_class_find_method_result="${full_name}"
+            return 0
+        fi
+    done
+
+    # TODO: better error / failure
+    >&2 echo "method $method not found via class $class"
+    return 1
+}
+
+# the method dispatcher
+function bos/meta/class/invoke() {
+    local class="$1";shift
+    local object_id="$1";shift
+    local method="$1";shift
+
+    local start_from_class=''
+
+    if [[ "$method" == 'next/method' ]]; then
+        # get the method and the calling class, so
+        # bos_find_class_for_method will return the *next* class to
+        # use
+        local caller; bos-dispatch/caller-into caller
+        method="${caller##*/}"
+        start_from_class="${caller%/*}"
+    fi
+
+    # get the first class that defines the method
+
+    # there is some fuckery going on with namerefs, recursion, and
+    # local; this is a probably-bad-but-works workaround: use a
+    # different variable name in different recursive calls
+    local ffsname="to_invoke_${#FUNCNAME[*]}"
+    $self find-method-into "$ffsname" "$class" "$start_from_class" "$method"
+
+    # TODO: make the fields accessible!
+
+    local self
+    bos-object-id/pack-self-into self "$class" "$object_id"
+
+    # call it
+    eval "\"\$$ffsname\" \"\$@\""
+    return $?
+}
+
+function bos/meta/class/create-object-into() {
+    local -n bos_meta_class_create_object_result="$1";shift
+    local class="$1";shift
+
+    local object_id_store; bos-namespaces/store-scalar-for-into object_id_store object_id "$class"
+    local -n object_id="$object_id_store"
+    (( ++object_id ))
+
+    bos-object-id/pack-self-into bos_meta_class_create_object_result "$class" "$object_id"
+
+    # TODO invoke BUILD/BUILDALL?
+
+    return 0
+}