#include <assert.h>

#include "hashmap.h"
#include "scope.h"

typedef struct apfl_value *variable;

void
apfl_scope_deinit(struct apfl_allocator allocator, struct scope *scope)
{
    (void)allocator;
    apfl_hashmap_deinit(&scope->map);
}

static bool
scope_keys_eq(void *opaque, const void *_a, const void *_b)
{
    (void)opaque;
    const struct apfl_string * const *a = _a;
    const struct apfl_string * const *b = _b;

    return apfl_string_eq(**a, **b);
}

static apfl_hash
scope_calc_hash(void *opaque, const void *_key)
{
    (void)opaque;
    const struct apfl_string *const*key = _key;
    struct apfl_string_view sv = apfl_string_view_from(**key);
    return apfl_hash_fnv1a(sv.bytes, sv.len);
}

struct scope *
apfl_scope_new(struct gc *gc)
{
    struct apfl_hashmap map;
    if (!apfl_hashmap_init(
        &map,
        gc->allocator,
        (struct apfl_hashmap_callbacks) {
            .opaque = NULL,
            .keys_eq = scope_keys_eq,
            .calc_hash = scope_calc_hash,
        },
        sizeof(struct apfl_string *),
        sizeof(variable)
    )) {
        return NULL;
    }

    struct scope *scope = apfl_gc_new_scope(gc);
    if (scope == NULL) {
        apfl_hashmap_deinit(&map);
        return NULL;
    }

    *scope = (struct scope) {
        .map = map,
    };

    return scope;
}

void
apfl_gc_var_traverse(struct apfl_value *var, gc_visitor cb, void *opaque)
{
    apfl_value_visit_gc_object(*var, cb, opaque);
}

void
apfl_gc_scope_traverse(struct scope *scope, gc_visitor cb, void *opaque)
{
    HASHMAP_EACH(&scope->map, cur) {
        struct apfl_string **k = apfl_hashmap_cursor_peek_key(cur);
        assert(k != NULL);
        cb(opaque, GC_OBJECT_FROM(*k, GC_TYPE_STRING));

        variable *v = apfl_hashmap_cursor_peek_value(cur);
        assert(v != NULL);
        cb(opaque, GC_OBJECT_FROM(*v, GC_TYPE_VAR));
    }
}

bool
apfl_scope_get(struct scope *scope, struct apfl_string *name, struct apfl_value *out)
{
    variable var;
    if (!apfl_hashmap_get(&scope->map, &name, &var)) {
        return false;
    }

    // The value is now in the variable and outside of it (presumably to be
    // saved onto the stack). We need to set the COW flag so a mutation of one
    // copy doesn't affect the other one.
    *out = apfl_value_set_cow_flag(*var);

    return true;
}

bool
apfl_scope_has(struct scope *scope, struct apfl_string *name)
{
    return apfl_hashmap_isset(&scope->map, &name);
}

static variable
get_or_create_variable(struct gc *gc, struct scope *scope, struct apfl_string *name)
{
    variable var;
    if (apfl_hashmap_get(&scope->map, &name, &var)) {
        return var;
    }

    struct apfl_hashmap_prepared_set prepared_set;
    if (!apfl_hashmap_prepare_set(&scope->map, &prepared_set, &name)) {
        return NULL;
    }

    var = apfl_gc_new_var(gc);
    if (var == NULL) {
        return NULL;
    }

    *var = (struct apfl_value) { .type = VALUE_NIL };
    apfl_hashmap_set_prepared(prepared_set, &var);

    return var;
}

bool
apfl_scope_set(struct gc *gc, struct scope *scope, struct apfl_string *name, struct apfl_value value)
{
    variable var = get_or_create_variable(gc, scope, name);
    if (var == NULL) {
        return false;
    }

    *var = value;
    return true;
}

bool
apfl_scope_update_existing(struct scope *scope, struct apfl_string *name, struct apfl_value value)
{
    variable var;
    if (!apfl_hashmap_get(&scope->map, &name, &var)) {
        return false;
    }

    *var = value;
    return true;
}

bool
apfl_scope_create_var(struct gc *gc, struct scope *scope, struct apfl_string *name)
{
    return get_or_create_variable(gc, scope, name) != NULL;
}

bool
apfl_scope_merge_into(struct scope *self, struct scope *other)
{
    if (self == NULL || other == NULL) {
        return NULL;
    }

    HASHMAP_EACH(&other->map, cur) {
        struct apfl_string **k = apfl_hashmap_cursor_peek_key(cur);
        assert(k != NULL);

        variable *v = apfl_hashmap_cursor_peek_value(cur);
        assert(v != NULL);

        if (!apfl_hashmap_set(&self->map, k, v)) {
            return false;
        }
    }

    return true;
}