/*
 * Copyright 2022-2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

use super::SchemaType;
use crate::ast::{EntityUID, Expr, ExprKind, Name, RestrictedExpr, RestrictedExpressionError};
use crate::extensions::ExtensionsError;
use smol_str::SmolStr;
use thiserror::Error;

/// Errors thrown during deserialization from JSON
#[derive(Debug, Error)]
pub enum JsonDeserializationError {
    /// Error thrown by `serde_json`
    #[error("{0}")]
    Serde(#[from] serde_json::Error),
    /// Contents of an `__expr` escape failed to parse as a Cedar expression.
    ///
    /// `__expr` is deprecated (starting with the 1.2 release), and once it is
    /// removed, this error will also be removed.
    #[error(transparent)]
    ExprParseError(crate::parser::err::ParseError),
    /// Contents of an `__entity` escape failed to parse as an entity reference
    #[error(transparent)]
    EntityParseError(crate::parser::err::ParseError),
    /// Function name in an `__extn` escape failed to parse as an extension function name
    #[error(transparent)]
    ExtnParseError(crate::parser::err::ParseError),
    /// Restricted expression error
    #[error(transparent)]
    RestrictedExpressionError(#[from] RestrictedExpressionError),
    /// Error thrown by an operation on `Extensions`
    #[error(transparent)]
    ExtensionsError(#[from] ExtensionsError),
    /// A field that needs to be a literal entity reference, was some other JSON value
    #[error("{ctx}, expected a literal entity reference, but got {got}")]
    ExpectedLiteralEntityRef {
        /// Context of this error
        ctx: JsonDeserializationErrorContext,
        /// the expression we got instead
        got: Box<Expr>,
    },
    /// A field that needs to be an extension value, was some other JSON value
    #[error("{ctx}, expected an extension value, but got {got}")]
    ExpectedExtnValue {
        /// Context of this error
        ctx: JsonDeserializationErrorContext,
        /// the expression we got instead
        got: Box<Expr>,
    },
    /// Contexts need to be records, but we got some other JSON value
    #[error("Expected Context to be a record, but got {got}")]
    ExpectedContextToBeRecord {
        /// Expression we got instead
        got: Box<RestrictedExpr>,
    },
    /// Schema-based parsing needed an implicit extension constructor, but no suitable
    /// constructor was found
    #[error("Extension constructor for {arg_type} -> {return_type} not found")]
    ImpliedConstructorNotFound {
        /// return type of the constructor we were looking for
        return_type: Box<SchemaType>,
        /// argument type of the constructor we were looking for
        arg_type: Box<SchemaType>,
    },
    /// During schema-based parsing, encountered this attribute on this entity, but that
    /// attribute shouldn't exist on entities of this type
    #[error("Attribute {:?} on {uid} shouldn't exist according to the schema", &.attr)]
    UnexpectedEntityAttr {
        /// Entity that had the unexpected attribute
        uid: EntityUID,
        /// Name of the attribute that was unexpected
        attr: SmolStr,
    },
    /// During schema-based parsing, encountered this attribute on a record, but
    /// that attribute shouldn't exist on that record
    #[error("{ctx}, record attribute {record_attr:?} shouldn't exist according to the schema")]
    UnexpectedRecordAttr {
        /// Context of this error
        ctx: JsonDeserializationErrorContext,
        /// Name of the (Record) attribute which was unexpected
        record_attr: SmolStr,
    },
    /// During schema-based parsing, didn't encounter this attribute of a
    /// record, but that attribute should have existed
    #[error("Expected {uid} to have an attribute {attr:?}, but it didn't")]
    MissingRequiredEntityAttr {
        /// Entity that is missing a required attribute
        uid: EntityUID,
        /// Name of the attribute which was expected
        attr: SmolStr,
    },
    /// During schema-based parsing, didn't encounter this attribute of a
    /// record, but that attribute should have existed
    #[error("{ctx}, expected the record to have an attribute {record_attr:?}, but it didn't")]
    MissingRequiredRecordAttr {
        /// Context of this error
        ctx: JsonDeserializationErrorContext,
        /// Name of the (Record) attribute which was expected
        record_attr: SmolStr,
    },
    /// During schema-based parsing, the given attribute on the given entity had
    /// a different type than the schema indicated to expect
    #[error("{ctx}, type mismatch: attribute was expected to have type {expected}, but actually has type {actual}")]
    TypeMismatch {
        /// Context of this error
        ctx: JsonDeserializationErrorContext,
        /// Type which was expected
        expected: Box<SchemaType>,
        /// Type which was encountered instead
        actual: Box<SchemaType>,
    },
    /// During schema-based parsing, found a set whose elements don't all have the
    /// same type.  This doesn't match any possible schema.
    #[error("{ctx}, set elements have different types: {ty1} and {ty2}")]
    HeterogeneousSet {
        /// Context of this error
        ctx: JsonDeserializationErrorContext,
        /// First element type which was found
        ty1: Box<SchemaType>,
        /// Second element type which was found
        ty2: Box<SchemaType>,
    },
}

/// Errors thrown during serialization to JSON
#[derive(Debug, Error)]
pub enum JsonSerializationError {
    /// Error thrown by `serde_json`
    #[error("{0}")]
    Serde(#[from] serde_json::Error),
    /// Extension-function calls with 0 arguments are not currently supported in
    /// our JSON format.
    #[error("extension-function calls with 0 arguments are not currently supported in our JSON format. found call of {func}")]
    ExtnCall0Arguments {
        /// Name of the function which was called with 0 arguments
        func: Name,
    },
    /// Extension-function calls with 2 or more arguments are not currently
    /// supported in our JSON format.
    #[error("extension-function calls with 2 or more arguments are not currently supported in our JSON format. found call of {func}")]
    ExtnCall2OrMoreArguments {
        /// Name of the function which was called with 2 or more arguments
        func: Name,
    },
    /// Encountered a `Record` which can't be serialized to JSON because it
    /// contains a key which is reserved as a JSON escape.
    #[error("record uses reserved key: {key}")]
    ReservedKey {
        /// Reserved key which was used by the `Record`
        key: SmolStr,
    },
    /// Encountered an `ExprKind` which we didn't expect. Either a case is
    /// missing in `JSONValue::from_expr()`, or an internal invariant was
    /// violated and there is a non-restricted expression in `RestrictedExpr`
    #[error("unexpected restricted expression: {kind:?}")]
    UnexpectedRestrictedExprKind {
        /// `ExprKind` which we didn't expect to find
        kind: ExprKind,
    },
}

/// Gives information about the context of a JSON deserialization error (e.g.,
/// where we were in the JSON document).
#[derive(Debug, Clone)]
pub enum JsonDeserializationErrorContext {
    /// The error occurred while deserializing the attribute `attr` of an entity.
    EntityAttribute {
        /// Entity where the error occurred
        uid: EntityUID,
        /// Attribute where the error occurred
        attr: SmolStr,
    },
    /// The error occurred while deserializing the `parents` field of an entity.
    EntityParents {
        /// Entity where the error occurred
        uid: EntityUID,
    },
    /// The error occurred while deserializing the `uid` field of an entity.
    EntityUid,
    /// The error occurred while deserializing the `Context`.
    Context,
}

impl std::fmt::Display for JsonDeserializationErrorContext {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::EntityAttribute { uid, attr } => write!(f, "In attribute {attr:?} on {uid}"),
            Self::EntityParents { uid } => write!(f, "In parents field of {uid}"),
            Self::EntityUid => write!(f, "In uid field of <unknown entity>"),
            Self::Context => write!(f, "While parsing Context"),
        }
    }
}