use crate::{
    diagnostics::{DatamodelError, DatamodelWarning, Diagnostics},
    parser_database::{
        ast::{WithName, WithSpan},
        walkers::{IndexWalker, ModelWalker, PrimaryKeyWalker, ScalarFieldWalker},
    },
};

/// If `@default(auto())`, then also `@db.ObjectId`
pub(super) fn objectid_type_required_with_auto_attribute(field: ScalarFieldWalker<'_>, errors: &mut Diagnostics) {
    if !field.default_value().map(|val| val.is_auto()).unwrap_or(false) {
        return;
    }

    if matches!(field.raw_native_type().map(|t| t.1), Some("ObjectId")) {
        return;
    }

    let container = if field.model().ast_model().is_view() {
        "view"
    } else {
        "model"
    };

    let err = DatamodelError::new_field_validation_error(
        "MongoDB `@default(auto())` fields must have `ObjectId` native type.",
        container,
        field.model().name(),
        field.name(),
        field.ast_field().span(),
    );

    errors.push_error(err);
}

/// If `@default(auto())`, then also `@id`.
pub(super) fn auto_attribute_must_be_an_id(field: ScalarFieldWalker<'_>, errors: &mut Diagnostics) {
    if field.is_single_pk() || field.is_part_of_a_compound_pk() {
        return;
    }

    if !field.default_value().map(|val| val.is_auto()).unwrap_or(false) {
        return;
    }

    let container = if field.model().ast_model().is_view() {
        "view"
    } else {
        "model"
    };

    let err = DatamodelError::new_field_validation_error(
        "MongoDB `@default(auto())` fields must have the `@id` attribute.",
        container,
        field.model().name(),
        field.name(),
        field.ast_field().span(),
    );

    errors.push_error(err);
}

/// `@default(dbgenerated())` is only for SQL connectors.
pub(super) fn dbgenerated_attribute_is_not_allowed(field: ScalarFieldWalker<'_>, errors: &mut Diagnostics) {
    if !field.default_value().map(|val| val.is_dbgenerated()).unwrap_or(false) {
        return;
    }

    let container = if field.model().ast_model().is_view() {
        "view"
    } else {
        "model"
    };

    let err = DatamodelError::new_field_validation_error(
        "The `dbgenerated()` function is not allowed with MongoDB. Please use `auto()` instead.",
        container,
        field.model().name(),
        field.name(),
        field.ast_field().span(),
    );
    errors.push_error(err);
}

/// The _id name check is superfluous because it's not a valid schema field at the moment.
pub(super) fn id_field_must_have_a_correct_mapped_name(pk: PrimaryKeyWalker<'_>, errors: &mut Diagnostics) {
    if pk.fields().len() > 1 {
        return;
    }

    let field = match pk.fields().next() {
        Some(field) => field,
        None => return,
    };

    if field.name() == "_id" || field.mapped_name() == Some("_id") {
        return;
    }

    let container = if field.model().ast_model().is_view() {
        "view"
    } else {
        "model"
    };

    let error = match field.mapped_name() {
        Some(name) => {
            let msg = format!("MongoDB model IDs must have an @map(\"_id\") annotation, found @map(\"{name}\").",);

            DatamodelError::new_field_validation_error(
                &msg,
                container,
                field.model().name(),
                field.name(),
                field.ast_field().span(),
            )
        }
        None => DatamodelError::new_field_validation_error(
            "MongoDB model IDs must have an @map(\"_id\") annotation.",
            container,
            field.model().name(),
            field.name(),
            field.ast_field().span(),
        ),
    };

    errors.push_error(error);
}

/// Must define one field as an `@id`.
pub(super) fn id_must_be_defined(model: ModelWalker<'_>, errors: &mut Diagnostics) {
    if model.primary_key().is_some() {
        return;
    }

    errors.push_error(DatamodelError::new_invalid_model_error(
        "MongoDB models require exactly one identity field annotated with @id",
        model.ast_model().span(),
    ));
}

/// We can define only one index with the same parameters.
pub(crate) fn index_is_not_defined_multiple_times_to_same_fields(index: IndexWalker<'_>, errors: &mut Diagnostics) {
    let attr = index.ast_attribute();

    let hits = index
        .model()
        .indexes()
        .filter(|i| i.attribute_id() != index.attribute_id())
        .filter(|i| i.contains_exactly_the_fields(index.scalar_field_attributes()))
        .count();

    if hits == 0 {
        return;
    }

    let attr_name = attr.name();

    errors.push_error(DatamodelError::new_attribute_validation_error(
        "Index already exists in the model.",
        &format!("@@{attr_name}"),
        attr.span(),
    ))
}

/// A field cannot have `@id` and `@unique` attributes at the same time.
pub(crate) fn unique_cannot_be_defined_to_id_field(index: IndexWalker<'_>, errors: &mut Diagnostics) {
    if !index.is_unique() {
        return;
    }

    if index.fields().len() != 1 {
        return;
    }

    let field = index.fields().next().unwrap();

    if !field.is_single_pk() {
        return;
    }

    errors.push_error(DatamodelError::new_attribute_validation_error(
        "The same field cannot be an id and unique on MongoDB.",
        index.attribute_name(),
        index.ast_attribute().span(),
    ));
}

/// A field name cannot contain the `.` character and it cannot start with `$`.
pub(crate) fn field_name_uses_valid_characters(field: ScalarFieldWalker<'_>, errors: &mut Diagnostics) {
    let name = match field.mapped_name() {
        Some(name) => name,
        None => return,
    };

    let span = field.ast_field().span_for_attribute("map").unwrap();

    if name.starts_with('$') {
        errors.push_error(DatamodelError::new_attribute_validation_error(
            "The field name cannot start with a `$` character",
            "@map",
            span,
        ));
    }

    if name.contains('.') {
        errors.push_error(DatamodelError::new_attribute_validation_error(
            "The field name cannot contain a `.` character",
            "@map",
            span,
        ));
    }
}

/// Makes sure underlying fields of a relation have the same native types.
pub(crate) fn relation_same_native_type(
    field: crate::parser_database::walkers::RelationFieldWalker<'_>,
    errors: &mut Diagnostics,
) {
    let references = field.referenced_fields();
    let fields = field.referencing_fields();

    if let (Some(fields), Some(references)) = (fields, references) {
        for (a_field, b_ref) in fields.into_iter().zip(references) {
            let field_nt = a_field.raw_native_type().map(|nt| (nt.0, nt.1));
            let ref_nt = b_ref.raw_native_type().map(|nt| (nt.0, nt.1));
            let span = a_field.ast_field().span();
            let a_model_name = a_field.model().name();
            let a_field_name = a_field.name();
            let b_model_name = b_ref.model().name();
            let b_field_name = b_ref.name();

            let msg = match (field_nt, ref_nt) {
                (Some(a), Some(b)) if a != b => {
                    format!(
                        "Field {a_model_name}.{a_field_name} and {b_model_name}.{b_field_name} must have the same native type for MongoDB to join those collections correctly. Consider updating those fields to either use '@{}.{}' or '@{}.{}'.",
                        a.0,
                        a.1,
                        b.0,
                        b.1
                    )
                }
                (None, Some(b)) => {
                    format!(
                        "Field {a_model_name}.{a_field_name} and {b_model_name}.{b_field_name} must have the same native type for MongoDB to join those collections correctly. Consider either removing {b_model_name}.{b_field_name}'s native type attribute or adding '@{}.{}' to {a_model_name}.{a_field_name}.",
                        b.0,
                        b.1
                    )
                }
                (Some(a), None) => {
                    format!(
                        "Field {a_model_name}.{a_field_name} and {b_model_name}.{b_field_name} must have the same native type for MongoDB to join those collections correctly. Consider either removing {a_model_name}.{a_field_name}'s native type attribute or adding '@{}.{}' to {b_model_name}.{b_field_name}.",
                        a.0,
                        a.1
                    )
                }
                _ => continue,
            };

            let msg = format!("{msg} Beware that this will become an error in the future.");

            errors.push_warning(DatamodelWarning::new_field_validation(
                &msg,
                field.model().name(),
                field.name(),
                span,
            ));
        }
    };
}