//! RFC 010 c2 — owned envelope tests (roadmap: per-frame roundtrip,
//! truncation mid-field, unknown tag, length prefix lying long and short,
//! zero-length payload, adversarial lengths).
#![cfg(feature = "cluster")]

use serde::{Deserialize, Serialize};
use smarm::cluster::envelope::{
    decode_payload, encode_payload, DecodeError, Frame, NodeMeta, RejectReason, MAX_FRAME_LEN,
    PROTO_VERSION,
};
use smarm::cluster::RemoteDownReason;
use smarm::monitor::DownReason;
use smarm::pg::Incarnation;

fn meta() -> NodeMeta {
    NodeMeta {
        role: "worker".into(),
        region: "eu-west".into(),
    }
}

fn all_frames() -> Vec<Frame> {
    vec![
        Frame::Hello {
            proto_version: PROTO_VERSION,
            build_hash: 0xDEAD_BEEF_CAFE_F00D,
            node_name: "alpha".into(),
            incarnation: Incarnation::new(7),
            meta: meta(),
        },
        Frame::HelloAck {
            node_name: "beta".into(),
            incarnation: Incarnation::new(9),
            meta: meta(),
        },
        Frame::HelloReject {
            reason: RejectReason::NameTaken,
        },
        Frame::Heartbeat,
        Frame::Send {
            index: 42,
            generation: 3,
            type_hash: 0x1234_5678_9ABC_DEF0,
            payload: vec![1, 2, 3, 4, 5],
        },
        Frame::SendNamed {
            name: "the_counter".into(),
            type_hash: 0xFFFF_0000_FFFF_0000,
            payload: vec![],
        },
        Frame::Monitor {
            monitor_id: 77,
            index: 42,
            generation: 3,
        },
        Frame::Demonitor { monitor_id: 77 },
        Frame::Down {
            monitor_id: 77,
            reason: RemoteDownReason::Local(DownReason::Panic),
        },
        Frame::Down {
            monitor_id: 78,
            reason: RemoteDownReason::Disconnected,
        },
    ]
}

fn encode_one(f: &Frame) -> Vec<u8> {
    let mut buf = Vec::new();
    f.encode(&mut buf).unwrap();
    buf
}

#[test]
fn per_frame_roundtrip() {
    for f in all_frames() {
        let buf = encode_one(&f);
        let (decoded, consumed) = Frame::decode(&buf).unwrap().unwrap();
        assert_eq!(decoded, f, "roundtrip mismatch");
        assert_eq!(consumed, buf.len(), "consumed != buffer length for {f:?}");
    }
}

#[test]
fn back_to_back_frames_decode_sequentially() {
    let mut buf = Vec::new();
    for f in all_frames() {
        f.encode(&mut buf).unwrap();
    }
    let mut off = 0;
    let mut decoded = Vec::new();
    while off < buf.len() {
        let (f, n) = Frame::decode(&buf[off..]).unwrap().unwrap();
        decoded.push(f);
        off += n;
    }
    assert_eq!(decoded, all_frames());
    assert_eq!(off, buf.len());
}

#[test]
fn heartbeat_golden_bytes() {
    // Locks the layout: u32 LE length prefix, then the tag byte.
    let buf = encode_one(&Frame::Heartbeat);
    assert_eq!(buf, vec![1, 0, 0, 0, 4]);
}

#[test]
fn zero_length_payload_roundtrips() {
    let f = Frame::Send {
        index: 0,
        generation: 0,
        type_hash: 0,
        payload: vec![],
    };
    let buf = encode_one(&f);
    let (decoded, consumed) = Frame::decode(&buf).unwrap().unwrap();
    assert_eq!(decoded, f);
    assert_eq!(consumed, buf.len());
}

#[test]
fn incomplete_is_none_not_error() {
    let buf = encode_one(&all_frames()[0]);
    // Every strict prefix short of the full frame must report "need more".
    for cut in 0..buf.len() {
        assert_eq!(
            Frame::decode(&buf[..cut]).unwrap(),
            None,
            "cut at {cut} should be incomplete"
        );
    }
}

#[test]
fn unknown_frame_tag() {
    let buf = vec![1, 0, 0, 0, 250];
    assert_eq!(Frame::decode(&buf), Err(DecodeError::UnknownTag(250)));
}

#[test]
fn unknown_enum_tags() {
    // HelloReject with a bogus reason tag.
    let buf = vec![2, 0, 0, 0, 3, 99];
    assert_eq!(
        Frame::decode(&buf),
        Err(DecodeError::UnknownEnumTag {
            what: "RejectReason",
            tag: 99
        })
    );
    // Down with a bogus reason tag (id = 0u64).
    let mut buf = vec![10, 0, 0, 0, 9];
    buf.extend_from_slice(&0u64.to_le_bytes());
    buf.push(200);
    assert_eq!(
        Frame::decode(&buf),
        Err(DecodeError::UnknownEnumTag {
            what: "RemoteDownReason",
            tag: 200
        })
    );
}

#[test]
fn length_prefix_lying_long_with_bytes_present_is_trailing() {
    let mut buf = encode_one(&Frame::Heartbeat);
    // Declare 3 extra body bytes and actually supply them.
    let declared = u32::from_le_bytes([buf[0], buf[1], buf[2], buf[3]]) + 3;
    buf[0..4].copy_from_slice(&declared.to_le_bytes());
    buf.extend_from_slice(&[0xAA, 0xBB, 0xCC]);
    assert_eq!(Frame::decode(&buf), Err(DecodeError::Trailing { extra: 3 }));
}

#[test]
fn length_prefix_lying_long_without_bytes_is_incomplete() {
    // Indistinguishable from a partial read — must be None, not an error.
    let mut buf = encode_one(&Frame::Heartbeat);
    let declared = u32::from_le_bytes([buf[0], buf[1], buf[2], buf[3]]) + 3;
    buf[0..4].copy_from_slice(&declared.to_le_bytes());
    assert_eq!(Frame::decode(&buf).unwrap(), None);
}

#[test]
fn length_prefix_lying_short_truncates_a_field() {
    let f = &all_frames()[0]; // Hello: plenty of fields to cut into
    let mut buf = encode_one(f);
    let declared = u32::from_le_bytes([buf[0], buf[1], buf[2], buf[3]]);
    let lie = declared - 4; // cut mid-field
    buf[0..4].copy_from_slice(&lie.to_le_bytes());
    assert_eq!(Frame::decode(&buf), Err(DecodeError::Truncated));
}

#[test]
fn truncation_mid_string_field() {
    // A frame whose declared length is intact but whose inner string length
    // runs past the body: SendNamed claiming a 1000-byte name in a tiny body.
    let mut body = vec![6u8]; // TAG_SEND_NAMED
    body.extend_from_slice(&1000u16.to_le_bytes());
    body.extend_from_slice(b"short");
    let mut buf = (body.len() as u32).to_le_bytes().to_vec();
    buf.extend_from_slice(&body);
    assert_eq!(Frame::decode(&buf), Err(DecodeError::Truncated));
}

#[test]
fn adversarial_lengths() {
    // Length prefix of u32::MAX: reject as oversized, do not wait for 4 GiB.
    let buf = [0xFF, 0xFF, 0xFF, 0xFF, 0];
    assert_eq!(
        Frame::decode(&buf),
        Err(DecodeError::FrameTooLarge {
            declared: u32::MAX as usize
        })
    );
    // Just over the cap: also rejected.
    let over = (MAX_FRAME_LEN as u32 + 1).to_le_bytes();
    assert!(matches!(
        Frame::decode(&over),
        Err(DecodeError::FrameTooLarge { .. })
    ));
    // Zero-length frame: there is no tag byte; corrupt, not incomplete.
    let buf = [0, 0, 0, 0];
    assert_eq!(Frame::decode(&buf), Err(DecodeError::EmptyFrame));
}

#[test]
fn invalid_utf8_in_string_field() {
    let mut buf = encode_one(&Frame::SendNamed {
        name: "abcd".into(),
        type_hash: 0,
        payload: vec![],
    });
    // name bytes start after: 4 (len) + 1 (tag) + 2 (str len) = offset 7
    buf[7] = 0xFF;
    assert_eq!(Frame::decode(&buf), Err(DecodeError::Utf8));
}

#[derive(Debug, PartialEq, Serialize, Deserialize)]
struct Ping {
    seq: u64,
    label: String,
}

#[test]
fn payload_seam_roundtrip() {
    let ping = Ping {
        seq: 31337,
        label: "hello".into(),
    };
    let blob = encode_payload(&ping).unwrap();
    // Carry it through a real frame, as it will travel in c9.
    let f = Frame::Send {
        index: 1,
        generation: 1,
        type_hash: 0xABCD,
        payload: blob,
    };
    let buf = encode_one(&f);
    let (decoded, _) = Frame::decode(&buf).unwrap().unwrap();
    let Frame::Send { payload, .. } = decoded else {
        panic!("wrong frame");
    };
    let back: Ping = decode_payload(&payload).unwrap();
    assert_eq!(back, ping);
}

#[test]
fn payload_seam_rejects_truncated_blob() {
    let blob = encode_payload(&Ping {
        seq: 1,
        label: "x".into(),
    })
    .unwrap();
    assert!(decode_payload::<Ping>(&blob[..blob.len() - 1]).is_err());
}