/*
 * Copyright (C) 2023 GNOME Foundation Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 *
 * Authors: Alice Mikhaylenko <alicem@gnome.org>
 */

#include "config.h"

#include "gtkcssreferencevalueprivate.h"

#include "gtkcssarrayvalueprivate.h"
#include "gtkcsscustompropertypoolprivate.h"
#include "gtkcssshorthandpropertyprivate.h"
#include "gtkcssstyleprivate.h"
#include "gtkcssunsetvalueprivate.h"
#include "gtkcssvalueprivate.h"
#include "gtkstyleproviderprivate.h"

#define GDK_ARRAY_NAME gtk_css_refs
#define GDK_ARRAY_TYPE_NAME GtkCssRefs
#define GDK_ARRAY_ELEMENT_TYPE gpointer
#define GDK_ARAY_PREALLOC 32
#define GDK_ARRAY_NO_MEMSET 1
#include "gdk/gdkarrayimpl.c"

#define MAX_TOKEN_LENGTH 65536

typedef enum {
  RESOLVE_SUCCESS,
  RESOLVE_INVALID,
  RESOLVE_ANIMATION_TAINTED,
} ResolveResult;

struct _GtkCssValue {
  GTK_CSS_VALUE_BASE

  GtkStyleProperty *property;
  GtkCssVariableValue *value;
  GFile *file;
  guint subproperty;
};

static void
gtk_css_value_reference_free (GtkCssValue *value)
{
  gtk_css_variable_value_unref (value->value);
  if (value->file)
    g_object_unref (value->file);
  g_free (value);
}

static ResolveResult
resolve_references_do (GtkCssVariableValue *value,
                       guint                property_id,
                       GtkCssVariableSet   *style_variables,
                       GtkCssVariableSet   *keyframes_variables,
                       gboolean             root,
                       GtkCssRefs          *refs,
                       gsize               *out_length,
                       gsize               *out_n_refs)
{
  GtkCssCustomPropertyPool *pool = gtk_css_custom_property_pool_get ();
  gsize i;
  gsize length = value->length;
  gsize n_refs = 0;
  ResolveResult ret = RESOLVE_SUCCESS;

  if (value->is_animation_tainted)
    {
      GtkCssStyleProperty *prop = _gtk_css_style_property_lookup_by_id (property_id);

      if (!_gtk_css_style_property_is_animated (prop))
        {
          /* Animation-tainted variables make other variables that reference
           * them animation-tainted too, so unlike regular invalid variables it
           * propagates to the root. For example, if --test is animation-tainted,
           * --test2: var(--test, fallback1); prop: var(--test2, fallback2); will\
           * resolve to fallback2 and _not_ to fallback1. So we'll propagate it
           * up until the root, and treat it same as invalid there instead. */
          ret = RESOLVE_ANIMATION_TAINTED;
          goto error;
        }
    }

  if (value->is_invalid)
    {
      ret = RESOLVE_INVALID;
      goto error;
    }

  if (!root)
    {
      n_refs += 1;
      gtk_css_refs_append (refs, value);
    }

  for (i = 0; i < value->n_references; i++)
    {
      GtkCssVariableValueReference *ref = &value->references[i];
      int id = gtk_css_custom_property_pool_lookup (pool, ref->name);
      GtkCssVariableValue *var_value = NULL;
      gsize var_length = 0, var_refs = 0;
      GtkCssVariableSet *source = style_variables;
      ResolveResult result = RESOLVE_INVALID;

      if (keyframes_variables)
        var_value = gtk_css_variable_set_lookup (keyframes_variables, id, NULL);

      if (!var_value && style_variables)
        var_value = gtk_css_variable_set_lookup (style_variables, id, &source);

      if (var_value)
        {
          result = resolve_references_do (var_value, property_id, source,
                                          keyframes_variables, FALSE,
                                          refs, &var_length, &var_refs);

          if (root && result == RESOLVE_ANIMATION_TAINTED)
            result = RESOLVE_INVALID;
        }

      if (result == RESOLVE_INVALID)
        {
          if (ref->fallback)
            {
              result = resolve_references_do (ref->fallback, property_id,
                                              style_variables, keyframes_variables,
                                              FALSE, refs, &var_length, &var_refs);

              if (root && result == RESOLVE_ANIMATION_TAINTED)
                result = RESOLVE_INVALID;
            }

          if (result != RESOLVE_SUCCESS)
            {
              ret = result;
              goto error;
            }
        }
      else if (result == RESOLVE_ANIMATION_TAINTED)
        {
          ret = RESOLVE_ANIMATION_TAINTED;
          goto error;
        }

      length += var_length - ref->length;
      n_refs += var_refs;

      if (length > MAX_TOKEN_LENGTH)
        {
          ret = RESOLVE_INVALID;
          goto error;
        }
    }

  if (out_length)
    *out_length = length;

  if (out_n_refs)
    *out_n_refs = n_refs;

  return ret;

error:
  /* Remove the references we added as if nothing happened */
  gtk_css_refs_splice (refs, gtk_css_refs_get_size (refs) - n_refs, n_refs, TRUE, NULL, 0);

  if (out_length)
    *out_length = 0;

  if (out_n_refs)
    *out_n_refs = 0;

  return ret;
}

static void
resolve_references (GtkCssVariableValue *input,
                    guint                property_id,
                    GtkCssStyle         *style,
                    GtkCssVariableSet   *keyframes_variables,
                    GtkCssRefs          *refs)
{
  if (resolve_references_do (input, property_id, style->variables,
                             keyframes_variables, TRUE, refs,
                             NULL, NULL) != RESOLVE_SUCCESS)
    {
      gtk_css_refs_clear (refs);
    }
}

static void
parser_error (GtkCssParser         *parser,
              const GtkCssLocation *start,
              const GtkCssLocation *end,
              const GError         *error,
              gpointer              user_data)
{
  GtkStyleProvider *provider = user_data;
  GError *new_error = NULL;
  GtkCssVariableValue **vars;
  char **names;
  gsize n_vars;

  gtk_css_parser_get_expanding_variables (parser, &vars, &names, &n_vars);

  if (n_vars > 0)
    {
      for (int i = 0; i < n_vars; i++)
        {
          GtkCssSection *section;

          if (names[i + 1])
            g_set_error (&new_error,
                         error->domain, error->code,
                         "While expanding %s: %s", names[i + 1], error->message);
          else
            g_set_error_literal (&new_error,
                                 error->domain, error->code,
                                 error->message);

          if (vars[i]->section == NULL)
            section = gtk_css_section_new (gtk_css_parser_get_file (parser), start, end);
          else
            section = gtk_css_section_ref (vars[i]->section);

          gtk_style_provider_emit_error (provider, section, new_error);

          gtk_css_section_unref (section);
          g_clear_error (&new_error);
        }

      for (int i = 0; i < n_vars; i++)
        {
          if (vars[i])
            gtk_css_variable_value_unref (vars[i]);
          g_free (names[i]);
        }

      g_free (vars);
      g_free (names);
    }
}

static GtkCssValue *
gtk_css_value_reference_compute (GtkCssValue          *value,
                                 guint                 property_id,
                                 GtkCssComputeContext *context)
{
  GtkCssValue *result = NULL, *computed;
  GtkCssRefs refs;
  guint shorthand_id = G_MAXUINT;

  if (GTK_IS_CSS_SHORTHAND_PROPERTY (value->property))
    {
      shorthand_id = _gtk_css_shorthand_property_get_id (GTK_CSS_SHORTHAND_PROPERTY (value->property));
      if (context->shorthands && context->shorthands[shorthand_id])
        {
          result = gtk_css_value_ref (context->shorthands[shorthand_id]);
          goto pick_subproperty;
        }
    }

  gtk_css_refs_init (&refs);

  resolve_references (value->value, property_id, context->style, context->variables, &refs);

  if (gtk_css_refs_get_size (&refs) > 0)
    {
      const GtkCssToken *token;

      GtkCssParser *value_parser =
        gtk_css_parser_new_for_token_stream (value->value,
                                             value->file,
                                             (GtkCssVariableValue **) refs.start,
                                             gtk_css_refs_get_size (&refs),
                                             parser_error, context->provider,
                                             NULL);

      result = _gtk_style_property_parse_value (value->property, value_parser);
      token = gtk_css_parser_peek_token (value_parser);
      if (!gtk_css_token_is (token, GTK_CSS_TOKEN_EOF))
        {
          char *junk;

          junk = gtk_css_token_to_string (token);
          gtk_css_parser_error_syntax (value_parser,
                                       "Junk at end of %s value: %s",
                                       value->property->name, junk);
          g_free (junk);

          g_clear_pointer (&result, gtk_css_value_unref);
        }
      gtk_css_parser_unref (value_parser);
    }

  gtk_css_refs_clear (&refs);

  if (result == NULL)
    result = _gtk_css_unset_value_new ();

  if (shorthand_id != G_MAXUINT)
    {
      GtkCssValue *sub;

      if (context->shorthands)
        {
          g_assert (context->shorthands[shorthand_id] == NULL);
          context->shorthands[shorthand_id] = gtk_css_value_ref (result);
        }

pick_subproperty:
      sub = gtk_css_value_ref (_gtk_css_array_value_get_nth (result, value->subproperty));
      gtk_css_value_unref (result);
      result = sub;
    }

  computed = gtk_css_value_compute (result, property_id, context);
  computed->is_computed = TRUE;

  gtk_css_value_unref (result);

  return computed;
}

static gboolean
gtk_css_value_reference_equal (const GtkCssValue *value1,
                               const GtkCssValue *value2)
{
  return FALSE;
}

static GtkCssValue *
gtk_css_value_reference_transition (GtkCssValue *start,
                                    GtkCssValue *end,
                                    guint        property_id,
                                    double       progress)
{
  return NULL;
}

static void
gtk_css_value_reference_print (const GtkCssValue *value,
                               GString           *string)
{
  gtk_css_variable_value_print (value->value, string);
}

static const GtkCssValueClass GTK_CSS_VALUE_REFERENCE = {
  "GtkCssReferenceValue",
  gtk_css_value_reference_free,
  gtk_css_value_reference_compute,
  NULL,
  gtk_css_value_reference_equal,
  gtk_css_value_reference_transition,
  NULL,
  NULL,
  gtk_css_value_reference_print
};

GtkCssValue *
_gtk_css_reference_value_new (GtkStyleProperty    *property,
                              GtkCssVariableValue *value,
                              GFile               *file)
{
  GtkCssValue *result;

  result = gtk_css_value_new (GtkCssValue, &GTK_CSS_VALUE_REFERENCE);
  result->property = property;
  result->value = gtk_css_variable_value_ref (value);
  result->contains_variables = TRUE;

  if (file)
    result->file = g_object_ref (file);
  else
    result->file = NULL;

  return result;
}

void
_gtk_css_reference_value_set_subproperty (GtkCssValue *value,
                                          guint        property)
{
  g_assert (GTK_IS_CSS_SHORTHAND_PROPERTY (value->property));

  value->subproperty = property;
}