From c9a935b161d644dab64a27cf9de933aec1681131 Mon Sep 17 00:00:00 2001
From: Laria Carolin Chabowski <laria@laria.me>
Date: Sat, 15 Jan 2022 23:09:24 +0100
Subject: [PATCH] Support assigning into dictionaries

You can now set keys in dictionaries to a value. If a key in a key path is
missing, we automatically create an empty dictionary. Otherwise setting
deeply nested keys becomes annoying.
---
 README.md   |   7 ++++
 src/apfl.h  |   1 +
 src/eval.c  | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 src/value.c |  11 ++++++
 4 files changed, 124 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 16f4fe0..f16982b 100644
--- a/README.md
+++ b/README.md
@@ -356,3 +356,10 @@ Also instead of assigning into variables you can assign into keys of a dictionar
     key = "baz"
     [d@key _] = [3 4]
     # d is now the dictionary ["foo" -> 1, "bar" -> 2, "baz" -> 3]
+
+The leftmost part must be a variable that contains a dictionary. Keys into that dictionary must either point to a dictionary or must not yet exist (in which case an empty dictionary is created automatically).
+
+    d = [->]
+    d.foo = 1
+    # d.foo.bar = 2  # Would result in an error as d.foo is not a dictionary.
+    d.bar.baz = 3    # Valid, the missing dict d.bar is autmatically created
diff --git a/src/apfl.h b/src/apfl.h
index 4b9d3fe..c64e64d 100644
--- a/src/apfl.h
+++ b/src/apfl.h
@@ -602,6 +602,7 @@ typedef struct apfl_editable_dict_data *apfl_editable_dict;
 
 apfl_editable_dict apfl_editable_dict_new(void);
 apfl_editable_dict apfl_editable_dict_new_from_dict(apfl_dict);
+bool apfl_editable_dict_get(apfl_editable_dict, struct apfl_value key, struct apfl_value *out);
 bool apfl_editable_dict_set(apfl_editable_dict, struct apfl_value key, struct apfl_value value);
 void apfl_editable_dict_delete(apfl_editable_dict, struct apfl_value key);
 void apfl_editable_dict_destroy(apfl_editable_dict);
diff --git a/src/eval.c b/src/eval.c
index 1198ef6..ed5dcda 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -785,6 +785,77 @@ match_pattern_match(struct match_pattern *pattern, struct apfl_value value)
     return MATCH_FATAL_ERROR;
 }
 
+static enum match_result
+match_pattern_apply_value_keys(
+    struct match_pattern_value *pattern_value,
+    apfl_editable_dict ed,
+    size_t i
+) {
+    struct apfl_value *key = &pattern_value->member_keys[i];
+
+    if (i == 0) {
+        if (!apfl_editable_dict_set(
+            ed,
+            apfl_value_incref(*key),
+            apfl_value_move(&pattern_value->value)
+        )) {
+            return MATCH_FATAL_ERROR;
+        }
+        return MATCH_OK;
+    }
+
+    apfl_editable_dict next_ed;
+
+    struct apfl_value value;
+    if (apfl_editable_dict_get(
+        ed,
+        apfl_value_incref(*key),
+        &value
+    )) {
+        if (value.type != APFL_VALUE_DICT) {
+            apfl_value_deinit(&value);
+            return MATCH_ERROR;
+        }
+
+        next_ed = apfl_editable_dict_new_from_dict(value.dict);
+    } else {
+        // Be nice and create the missing dictionary
+        next_ed = apfl_editable_dict_new();
+    }
+
+    if (next_ed == NULL) {
+        return MATCH_FATAL_ERROR;
+    }
+
+    enum match_result result = match_pattern_apply_value_keys(
+        pattern_value,
+        next_ed,
+        i - 1
+    );
+    if (result != MATCH_OK) {
+        apfl_editable_dict_destroy(next_ed);
+        return result;
+    }
+
+    apfl_dict next_dict = apfl_editable_dict_finalize(next_ed);
+    if (next_dict == NULL) {
+        return MATCH_FATAL_ERROR;
+    }
+
+    if (!apfl_editable_dict_set(
+        ed,
+        apfl_value_incref(*key),
+        (struct apfl_value) {
+            .type = APFL_VALUE_DICT,
+            .dict = next_dict,
+        }
+    )) {
+        return MATCH_FATAL_ERROR;
+    }
+
+    return MATCH_OK;
+}
+
 static enum match_result
 match_pattern_apply_value(struct match_pattern_value *pattern_value)
 {
@@ -792,11 +863,42 @@ match_pattern_apply_value(struct match_pattern_value *pattern_value)
         return false;
     }
 
-    if (pattern_value->member_keys_len > 0) {
-        return MATCH_NOT_YET_IMPLEMENTED;
+    if (pattern_value->member_keys_len == 0) {
+        variable_set(pattern_value->var, apfl_value_move(&pattern_value->value));
+        return MATCH_OK;
     }
 
-    variable_set(pattern_value->var, apfl_value_move(&pattern_value->value));
+    if (pattern_value->var->value.type != APFL_VALUE_DICT) {
+        return MATCH_ERROR;
+    }
+
+    apfl_editable_dict ed = apfl_editable_dict_new_from_dict(
+        apfl_dict_incref(pattern_value->var->value.dict)
+    );
+    if (ed == NULL) {
+        return MATCH_FATAL_ERROR;
+    }
+
+    enum match_result result = match_pattern_apply_value_keys(
+        pattern_value,
+        ed,
+        pattern_value->member_keys_len - 1
+    );
+    if (result != MATCH_OK) {
+        apfl_editable_dict_destroy(ed);
+        return result;
+    }
+
+    apfl_dict d = apfl_editable_dict_finalize(ed);
+    if (d == NULL) {
+        return MATCH_FATAL_ERROR;
+    }
+
+    variable_set(pattern_value->var, (struct apfl_value) {
+        .type = APFL_VALUE_DICT,
+        .dict = d,
+    });
+
     return MATCH_OK;
 }
 
diff --git a/src/value.c b/src/value.c
index 6a9f1d7..61ba4b7 100644
--- a/src/value.c
+++ b/src/value.c
@@ -506,6 +506,17 @@ apfl_editable_dict_new_from_dict(apfl_dict dict)
     return ed;
 }
 
+bool
+apfl_editable_dict_get(
+    apfl_editable_dict ed,
+    struct apfl_value key,
+    struct apfl_value *out
+) {
+    bool ok = apfl_hashmap_get(ed->map, &key, out);
+    apfl_value_deinit(&key);
+    return ok;
+}
+
 bool
 apfl_editable_dict_set(apfl_editable_dict ed, struct apfl_value key, struct apfl_value value)
 {