use crate::database::schema::Schema;

impl Schema {
  pub fn compile_polymorphism(
    &self,
    db: &crate::database::Database,
    root_id: &str,
    path: &str,
    errors: &mut Vec<crate::drop::Error>,
  ) {
    let mut options = std::collections::BTreeMap::new();
    let mut strategy = String::new();

    if let Some(family) = &self.obj.family {
      // Formalize the <Variant>.<Base> topology
      // family_base extracts the 'Base' (e.g. 'widget', 'person')
      let family_base = family.split('.').next_back().unwrap_or(family).to_string();
      // family_prefix extracts the 'Variant' (e.g. 'stock', 'light')
      let family_prefix = family
        .strip_suffix(&family_base)
        .unwrap_or("")
        .trim_end_matches('.');

      if let Some(type_def) = db.types.get(&family_base) {
        if type_def.variations.len() > 1 && type_def.variations.iter().any(|v| v != &family_base) {
          // Scenario A / B: Table Variations
          strategy = "type".to_string();
          for var in &type_def.variations {
            let target_id = if family_prefix.is_empty() {
              var.to_string()
            } else {
              format!("{}.{}", family_prefix, var)
            };

            if db.schemas.get(&target_id).is_some() {
              options.insert(var.to_string(), (None, Some(target_id)));
            }
          }
        } else {
          // Scenario C: Single Table Inheritance (Horizontal)
          strategy = "kind".to_string();

          let suffix = format!(".{}", family_base);

          for (id, schema) in &type_def.schemas {
            if id.ends_with(&suffix) || id == &family_base {
              if let Some(kind_val) = schema.obj.get_discriminator_value("kind", id) {
                options.insert(kind_val, (None, Some(id.to_string())));
              }
            }
          }
        }
      }
    } else if let Some(one_of) = &self.obj.one_of {
      let mut type_vals = std::collections::HashSet::new();
      let mut kind_vals = std::collections::HashSet::new();
      let mut disjoint_base = true;
      let mut structural_types = std::collections::HashSet::new();

      for c in one_of {
        let mut child_id = String::new();
        let mut child_is_primitive = false;

        if let Some(crate::database::object::SchemaTypeOrArray::Single(t)) = &c.obj.type_ {
          if crate::database::object::is_primitive_type(t) {
            child_is_primitive = true;
            structural_types.insert(t.clone());
          } else {
            child_id = t.clone();
            structural_types.insert("object".to_string());
          }
        } else {
          disjoint_base = false;
        }

        if !child_is_primitive {
          if let Some(t_val) = c.obj.get_discriminator_value("type", &child_id) {
            type_vals.insert(t_val);
          }
          if let Some(k_val) = c.obj.get_discriminator_value("kind", &child_id) {
            kind_vals.insert(k_val);
          }
        }
      }

      if disjoint_base && structural_types.len() == one_of.len() {
        strategy = "".to_string();
        for (i, c) in one_of.iter().enumerate() {
          if let Some(crate::database::object::SchemaTypeOrArray::Single(t)) = &c.obj.type_ {
            if crate::database::object::is_primitive_type(t) {
              options.insert(t.clone(), (Some(i), None));
            } else {
              options.insert("object".to_string(), (Some(i), None));
            }
          }
        }
      } else {
        strategy = if type_vals.len() > 1 && type_vals.len() == one_of.len() {
          "type".to_string()
        } else if kind_vals.len() > 1 && kind_vals.len() == one_of.len() {
          "kind".to_string()
        } else {
          "".to_string()
        };

        if strategy.is_empty() {
          errors.push(crate::drop::Error {
                 code: "AMBIGUOUS_POLYMORPHISM".to_string(),
                 message: format!("oneOf boundaries must map mathematically unique 'type' or 'kind' discriminators, or strictly contain disjoint primitive types."),
                 details: crate::drop::ErrorDetails {
                    path: Some(path.to_string()),
                    schema: Some(root_id.to_string()),
                    ..Default::default()
                 }
             });
          return;
        }

        for (i, c) in one_of.iter().enumerate() {
          let mut child_id = String::new();
          if let Some(crate::database::object::SchemaTypeOrArray::Single(t)) = &c.obj.type_ {
            if !crate::database::object::is_primitive_type(t) {
              child_id = t.clone();
            }
          }

          if let Some(val) = c.obj.get_discriminator_value(&strategy, &child_id) {
            if options.contains_key(&val) {
              errors.push(crate::drop::Error {
                  code: "POLYMORPHIC_COLLISION".to_string(),
                  message: format!("Polymorphic boundary defines multiple candidates mapped to the identical discriminator value '{}'.", val),
                  details: crate::drop::ErrorDetails {
                     path: Some(path.to_string()),
                     schema: Some(root_id.to_string()),
                     ..Default::default()
                  }
                });
              continue;
            }

            options.insert(val, (Some(i), None));
          }
        }
      }
    } else {
      return;
    }

    if !options.is_empty() {
      if !strategy.is_empty() {
        let _ = self.obj.compiled_discriminator.set(strategy);
      }
      let _ = self.obj.compiled_options.set(options);
    }
  }
}