exochain-gatekeeper 0.2.0-beta

// Copyright 2026 Exochain Foundation
//
// 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.
//
// SPDX-License-Identifier: Apache-2.0

//! Gatekeeper-specific errors.

use thiserror::Error;

/// Top-level error type for the gatekeeper crate.
#[derive(Debug, Error, Clone, PartialEq, Eq)]
pub enum GatekeeperError {
    #[error("kernel integrity check failed: expected {expected}, got {actual}")]
    KernelIntegrityFailure { expected: String, actual: String },

    #[error("invariant violation: {0}")]
    InvariantViolation(String),

    #[error("combinator reduction failed: {0}")]
    CombinatorError(String),

    #[error("holon error: {0}")]
    HolonError(String),

    #[error("MCP violation: {0}")]
    McpViolation(String),

    #[error("MCP typed signature payload encoding failed: {reason}")]
    McpTypedSignatureEncodingFailed { reason: String },

    #[error("TEE attestation failed: {0}")]
    TeeError(String),

    #[error("capability denied: {0}")]
    CapabilityDenied(String),

    #[error("authority resolver unavailable: {0}")]
    AuthorityResolverUnavailable(String),

    #[error("timeout after {0} ms")]
    Timeout(u64),

    #[error("checkpoint error: {0}")]
    CheckpointError(String),

    #[error("core error: {0}")]
    Core(String),

    #[error("MCP audit chain broken at index {index}")]
    McpAuditChainBroken { index: usize },

    #[error("MCP audit record invalid: {reason}")]
    McpAuditInvalidRecord { reason: String },

    #[error("MCP audit hash encoding failed: {reason}")]
    McpAuditHashEncodingFailed { reason: String },
}

impl From<exo_core::ExoError> for GatekeeperError {
    fn from(e: exo_core::ExoError) -> Self {
        GatekeeperError::Core(e.to_string())
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn display_all_variants() {
        let cases: Vec<(GatekeeperError, &str)> = vec![
            (
                GatekeeperError::KernelIntegrityFailure {
                    expected: "abc".into(),
                    actual: "def".into(),
                },
                "abc",
            ),
            (GatekeeperError::InvariantViolation("bad".into()), "bad"),
            (GatekeeperError::CombinatorError("fail".into()), "fail"),
            (GatekeeperError::HolonError("holon".into()), "holon"),
            (GatekeeperError::McpViolation("mcp".into()), "mcp"),
            (
                GatekeeperError::McpTypedSignatureEncodingFailed {
                    reason: "canonical CBOR failed".into(),
                },
                "canonical CBOR failed",
            ),
            (GatekeeperError::TeeError("tee".into()), "tee"),
            (GatekeeperError::CapabilityDenied("cap".into()), "cap"),
            (
                GatekeeperError::AuthorityResolverUnavailable("pool absent".into()),
                "authority resolver unavailable",
            ),
            (GatekeeperError::Timeout(500), "500"),
            (GatekeeperError::CheckpointError("ckpt".into()), "ckpt"),
            (GatekeeperError::Core("core".into()), "core"),
            (
                GatekeeperError::McpAuditInvalidRecord {
                    reason: "missing deterministic metadata".into(),
                },
                "missing deterministic metadata",
            ),
            (
                GatekeeperError::McpAuditHashEncodingFailed {
                    reason: "canonical CBOR failed".into(),
                },
                "canonical CBOR failed",
            ),
        ];
        for (err, fragment) in cases {
            assert!(err.to_string().contains(fragment), "{err}");
        }
    }

    #[test]
    fn from_exo_error() {
        let exo = exo_core::ExoError::InvalidDid { value: "x".into() };
        let gk = GatekeeperError::from(exo);
        assert!(matches!(gk, GatekeeperError::Core(_)));
    }
}