From 6297ec2ae4263c346a9f7cf036055ca8cdb72c78 Mon Sep 17 00:00:00 2001
From: Gianni Ceccarelli <gianni.ceccarelli@broadbean.com>
Date: Fri, 14 Jul 2023 15:22:38 +0100
Subject: inheritance via MOP

*probably*, I'm still not completely certain I've found all the
weirdness
---
 bos-dispatch.sh        |  6 +++---
 bos-mop-inheritance.sh | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++
 bos-mop.sh             | 18 ++++++++++++++----
 test.sh                | 12 ++++++++----
 4 files changed, 76 insertions(+), 11 deletions(-)
 create mode 100644 bos-mop-inheritance.sh

diff --git a/bos-dispatch.sh b/bos-dispatch.sh
index cb883d8..afefb5e 100644
--- a/bos-dispatch.sh
+++ b/bos-dispatch.sh
@@ -6,10 +6,9 @@ function bos-dispatch/invoke() {
     local self_id="$1";shift
     local method="$1";shift
 
-    local self
-    bos-object-id/pack-self-into "$class" "$self_id" self
-
     if declare -F "$class/$method" >/dev/null; then
+        local self
+        bos-object-id/pack-self-into "$class" "$self_id" self
         "$class/$method" "$@"
         return $?
     fi
@@ -19,4 +18,5 @@ function bos-dispatch/invoke() {
     local -n metaclass_object="$metaclass_ref"
 
     $metaclass_object invoke "$class" "$self_id" "$method" "$@"
+    return $?
 }
diff --git a/bos-mop-inheritance.sh b/bos-mop-inheritance.sh
new file mode 100644
index 0000000..551dd18
--- /dev/null
+++ b/bos-mop-inheritance.sh
@@ -0,0 +1,51 @@
+#!bash
+
+# this encoding must match bos-namespaces/encode-into
+bos_5fbos_2fmop_2finheritance_5fmeta="bos-dispatch/invoke bos/mop/base 0"
+declare -a bos_5fbos_2fmop_2finheritance_5fmro=( "bos/mop/inheritance" "bos/mop/base" )
+
+function bos/mop/inheritance/isa-for-into() {
+    bos-namespaces/store-array-for-into isa "$1" "$2"
+}
+
+function bos/mop/inheritance/set-superclasses-for() {
+    local isa_name; $self isa-for-into "$1" isa_name
+    local -n isa="$isa_name"
+    shift
+
+    isa=( "$@" )
+
+    return 0
+}
+
+function bos/mop/inheritance/get-superclasses-for-into() {
+    local isa_name; $self isa-for-into "$1" isa_name
+    local -n isa="$isa_name"
+    local -n dest="$2"
+
+    dest=( "${isa[@]}" )
+
+    return 0
+}
+
+# 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/mop/inheritance/make-mro-for() {
+    local class="$1"
+    local mro_name; $self mro-for-into "$class" mro_name
+    local -n mro="$mro_name"
+
+    # TODO: use C3 and support multiple inheritance
+
+    mro=( "$class" )
+    local -a nextclasses
+    $self get-superclasses-for-into "$class" nextclasses
+
+    while [[ "${#nextclasses}" -gt 0 ]]; do
+        mro+=( "${nextclasses[0]}" )
+        class="${nextclasses[0]}"
+        $self get-superclasses-for-into "$class" nextclasses
+    done
+
+    return 0
+}
diff --git a/bos-mop.sh b/bos-mop.sh
index 3b06216..b3b03f0 100644
--- a/bos-mop.sh
+++ b/bos-mop.sh
@@ -23,6 +23,12 @@ function bos/mop/base/find-method-into() {
 
     local mro_store; $self mro-for-into "$class" mro_store
     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
@@ -67,14 +73,18 @@ function bos/mop/base/invoke() {
     fi
 
     # get the first class that defines the method
-    local to_invoke
-    $self find-method-into "$class" "$start_from_class" "$method" to_invoke
+
+    # 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[*]}"
+    $self find-method-into "$class" "$start_from_class" "$method" "$ffsname"
 
     # TODO: make the fields accessible!
 
-    local self
     bos-object-id/pack-self-into "$class" "$object_id" self
 
     # call it
-    "$to_invoke" "$@"
+    eval "\"\$$ffsname\" \"\$@\""
+    return $?
 }
diff --git a/test.sh b/test.sh
index 1a4ed6d..4a3e02c 100644
--- a/test.sh
+++ b/test.sh
@@ -1,19 +1,23 @@
 #!/bin/bash
 
+PS4='[${#FUNCNAME[*]}] ${BASH_SOURCE[0]}:${LINENO} (${FUNCNAME[0]}) +'
+
 . bos-namespaces.sh
 . bos-object-id.sh
 . bos-mop.sh
 . bos-dispatch.sh
+. bos-mop-inheritance.sh
 
-bos_5fA_5fmeta="bos-dispatch/invoke bos/mop/base 0"
-bos_5fA_5fmro=( "A" )
+bos_5fA_5fmeta="bos-dispatch/invoke bos/mop/inheritance 0"
 
 function A/thing() {
     echo "<$self> A/thing ($*)"
 }
 
-bos_5fB_5fmeta="bos-dispatch/invoke bos/mop/base 0"
-bos_5fB_5fmro=( "B" "A" )
+
+bos_5fB_5fmeta="bos-dispatch/invoke bos/mop/inheritance 0"
+$bos_5fB_5fmeta set-superclasses-for B A
+$bos_5fB_5fmeta make-mro-for B
 
 function B/other() {
     echo "<$self> B/other ($*)"
-- 
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