/*
 * Copyright Cedar Contributors
 *
 * 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 std::sync::Arc;

use crate::ast;
use crate::ast::PolicySetError;
use crate::entities::JsonDeserializationError;
use crate::parser::err::{parse_errors, ParseErrors};
use crate::parser::{join_with_conjunction, unescape};
use miette::Diagnostic;
use nonempty::NonEmpty;
use smol_str::SmolStr;
use thiserror::Error;

/// Errors arising while converting a policy from its JSON representation (aka EST) into an AST
#[derive(Debug, Diagnostic, Error)]
pub enum FromJsonError {
    /// Error while deserializing JSON
    #[error(transparent)]
    #[diagnostic(transparent)]
    JsonDeserializationError(#[from] JsonDeserializationError),
    /// Tried to convert an EST representing a template to an AST representing a static policy
    #[error(transparent)]
    #[diagnostic(transparent)]
    TemplateToPolicy(#[from] parse_errors::ExpectedStaticPolicy),
    /// Tried to convert an EST representing a static policy to an AST representing a template
    #[error(transparent)]
    #[diagnostic(transparent)]
    PolicyToTemplate(#[from] parse_errors::ExpectedTemplate),
    /// Slot name was not valid for the position it was used in. (Currently, principal slots must
    /// be named `?principal`, and resource slots must be named `?resource`.)
    #[error("invalid slot name or slot used in wrong position")]
    #[diagnostic(help(
        "principal slots must be named `?principal` and resource slots must be named `?resource`"
    ))]
    InvalidSlotName,
    /// EST contained a template slot for `action`. This is not currently allowed
    #[error("slots are not allowed for actions")]
    ActionSlot,
    /// EST contained a template slot in policy condition
    #[error("found template slot {slot} in a `{clausetype}` clause")]
    #[diagnostic(help("slots are currently unsupported in `{clausetype}` clauses"))]
    SlotsInConditionClause {
        /// Slot that was found in a when/unless clause
        slot: ast::SlotId,
        /// Clause type, e.g. "when" or "unless"
        clausetype: &'static str,
    },
    /// EST contained the empty JSON object `{}` where a key (operator) was expected
    #[error("missing operator, found empty object")]
    MissingOperator,
    /// EST contained an object with multiple keys (operators) where a single operator was expected
    #[error("found multiple operators where one was expected: {ops:?}")]
    MultipleOperators {
        /// the multiple operators that were found where one was expected
        ops: Vec<SmolStr>,
    },
    /// At most one of the operands in `a * b * c * d * ...` can be a non-{constant int}
    #[error(
        "multiplication must be by a constant int: neither `{arg1}` nor `{arg2}` is a constant"
    )]
    MultiplicationByNonConstant {
        /// First non-constant argument
        arg1: ast::Expr,
        /// Second non-constant argument
        arg2: ast::Expr,
    },
    /// Error thrown while processing string escapes
    // show just the first error in the main error message, like in [`ParseErrors`]; see #326 and discussion on #477
    #[error("{}", match .0.first() { Some(err) => format!("{err}"), None => "invalid escape".into() })]
    UnescapeError(#[related] Vec<unescape::UnescapeError>),
    /// Error reported when the entity type tested by an `is` expression cannot be parsed.
    #[error("invalid entity type: {0}")]
    #[diagnostic(transparent)]
    InvalidEntityType(ParseErrors),
    /// Error reported when a policy set has duplicate ids
    #[error("Error creating policy set: {0}")]
    #[diagnostic(transparent)]
    PolicySet(#[from] PolicySetError),
    /// Error reported when attempting to create a template-link
    #[error("Error linking policy set: {0}")]
    #[diagnostic(transparent)]
    Linking(#[from] ast::LinkingError),
    /// Error reported when the extension function name is unknown
    #[error("Invalid extension function name: `{0}`")]
    UnknownExtFunc(ast::Name),
    /// Returned when an Entity UID used as an action does not have the type `Action`
    #[error(transparent)]
    #[diagnostic(transparent)]
    InvalidActionType(#[from] InvalidActionType),
}

/// Details about an `InvalidActionType` error.
#[derive(Debug, Diagnostic, Error)]
#[diagnostic(help("action entities must have type `Action`, optionally in a namespace"))]
pub struct InvalidActionType {
    pub(crate) euids: NonEmpty<Arc<crate::ast::EntityUID>>,
}

impl std::fmt::Display for InvalidActionType {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "expected that action entity uids would have the type `Action` but got "
        )?;
        join_with_conjunction(f, "and", self.euids.iter(), |f, e| write!(f, "`{e}`"))
    }
}

/// Errors while instantiating a policy
#[derive(Debug, PartialEq, Diagnostic, Error)]
pub enum InstantiationError {
    /// Template contains this slot, but a value wasn't provided for it
    #[error("failed to instantiate template: no value provided for `{slot}`")]
    MissedSlot {
        /// Slot which didn't have a value provided for it
        slot: ast::SlotId,
    },
}

impl From<ast::UnexpectedSlotError> for FromJsonError {
    fn from(err: ast::UnexpectedSlotError) -> Self {
        Self::TemplateToPolicy(err.into())
    }
}