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// Copyright 2020 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use crate::labels::NodeId;
use anyhow::Error;
use std::sync::Arc;

pub static TEST_ROUTER_INTERVAL: std::time::Duration = std::time::Duration::from_millis(500);

/// Generates node id's for tests in a repeatable fashion.
pub struct NodeIdGenerator {
    test_id: u64,
    test_name: &'static str,
    run: u64,
    n: u64,
}

impl Iterator for NodeIdGenerator {
    type Item = NodeId;
    fn next(&mut self) -> Option<NodeId> {
        let id = self.n;
        if id >= 100 {
            return None;
        }
        self.n += 1;
        Some(self.node_id(id))
    }
}

impl NodeIdGenerator {
    /// Create a new generator; uses the test name as salt for the node id's generated.
    pub fn new(test_name: &'static str, run: usize) -> NodeIdGenerator {
        NodeIdGenerator {
            test_id: crc::crc16::checksum_x25(test_name.as_bytes()) as u64,
            test_name,
            run: run as u64,
            n: 1,
        }
    }

    /// Create a new router with a unique (within this test run) node id.
    pub fn new_router(&mut self) -> Result<Arc<crate::router::Router>, Error> {
        crate::router::Router::with_node_id(
            self.next().ok_or(anyhow::format_err!("No more node ids available"))?,
            None,
        )
    }

    /// Like [`new_router`] but enables circuit route forwarding.
    pub fn new_router_circuit_router(&mut self) -> Result<Arc<crate::router::Router>, Error> {
        crate::router::Router::with_node_id(
            self.next().ok_or(anyhow::format_err!("No more node ids available"))?,
            Some(TEST_ROUTER_INTERVAL),
        )
    }

    /// Returns a string describing this test (including the base node id so it can be grepped).
    pub fn test_desc(&self) -> String {
        format!("({}) {}", self.node_id(0).0, self.test_name)
    }

    /// Generate the `idx` node id in this set.
    pub fn node_id(&self, idx: u64) -> NodeId {
        (self.test_id * 10000 * 100000 + self.run * 10000 + idx).into()
    }
}

#[cfg(test)]
mod test {

    #[fuchsia::test]
    fn node_id_generator_works() {
        let n = super::NodeIdGenerator::new("foo", 3);
        assert_eq!(n.node_id(1), 26676000030001.into());
        assert_eq!(&n.test_desc(), "(26676000030000) foo");
    }
}