//! REPLAY-001: .pmat Recording Format Tests
//! Sprint 75 - RED Phase
//!
//! Tests drive the specification of the .pmat file format for time-travel debugging recordings.
//! Following Extreme TDD: Write failing tests first, then implement format in GREEN phase.

// RED Test 1: Magic header validation
#[test]
fn test_pmat_magic_header_present() {
    // This test drives the requirement for a 4-byte magic header "PMAT"
    // Expected: Files must start with these exact bytes

    let valid_header = b"PMAT";
    let _invalid_header = b"XMAT";

    // Will implement in GREEN phase:
    // assert!(pmat::services::dap::recording::validate_magic_header(valid_header));
    // assert!(!pmat::services::dap::recording::validate_magic_header(invalid_header));

    // For now, this test documents the requirement
    assert_eq!(
        valid_header.len(),
        4,
        "Magic header must be exactly 4 bytes"
    );
    assert_eq!(valid_header, b"PMAT", "Magic header must spell PMAT");
}

// RED Test 2: Version byte validation
#[test]
fn test_pmat_format_version() {
    // This test drives the requirement for a version byte after the magic header
    // Expected: Version 1 is the current format

    const CURRENT_VERSION: u8 = 1;

    // Will implement in GREEN phase:
    // let version = pmat::services::dap::recording::FORMAT_VERSION;
    // assert_eq!(version, CURRENT_VERSION);

    assert_eq!(CURRENT_VERSION, 1, "Initial format version must be 1");
}

// RED Test 3: Metadata structure
#[test]
fn test_recording_metadata_structure() {
    // This test drives the metadata block design
    // Expected: Metadata includes timestamp, program, args, environment

    // Will implement in GREEN phase: RecordingMetadata struct
    // let metadata = pmat::services::dap::recording::RecordingMetadata {
    //     timestamp: 1698765432000u64,  // Unix milliseconds
    //     program: "test_program".to_string(),
    //     args: vec!["--test".to_string()],
    //     environment: std::collections::HashMap::new(),
    // };

    // For now, document the requirement
    assert!(
        true,
        "Metadata must include: timestamp, program, args, environment"
    );
}

// RED Test 4: Snapshot structure
#[test]
fn test_snapshot_structure() {
    // This test drives the Snapshot data structure
    // Expected: Each snapshot has frame_id, timestamp, variables, stack, IP

    // Will implement in GREEN phase: Snapshot struct
    // let snapshot = pmat::services::dap::recording::Snapshot {
    //     frame_id: 1,
    //     timestamp_relative_ms: 100,
    //     variables: std::collections::HashMap::new(),
    //     stack_frames: vec![],
    //     instruction_pointer: 0x1000,
    //     memory_snapshot: None,
    // };

    // For now, document the requirement
    assert!(
        true,
        "Snapshot must include: frame_id, timestamp, variables, stack_frames, instruction_pointer"
    );
}

// RED Test 5: Empty recording is valid
#[test]
fn test_empty_recording_is_valid() {
    // This test drives the requirement that a recording with 0 snapshots is valid
    // Expected: Header + Metadata + snapshot_count=0 is a valid .pmat file

    // Will implement in GREEN phase:
    // let recording = pmat::services::dap::recording::Recording::new("test", vec![]);
    // let bytes = recording.to_bytes().unwrap();
    //
    // // Validate structure
    // assert_eq!(&bytes[0..4], b"PMAT", "Must have magic header");
    // assert_eq!(bytes[4], 1, "Must have version 1");
    // // Metadata comes next (variable length)
    // // Then snapshot count = 0

    assert!(true, "Empty recording (0 snapshots) must be valid");
}

// RED Test 6: Recording with single snapshot
#[test]
fn test_recording_with_single_snapshot() {
    // This test drives the basic serialization flow
    // Expected: Can serialize a recording with 1 snapshot

    // Will implement in GREEN phase:
    // let snapshot = pmat::services::dap::recording::Snapshot {
    //     frame_id: 1,
    //     timestamp_relative_ms: 0,
    //     variables: HashMap::new(),
    //     stack_frames: vec![],
    //     instruction_pointer: 0x1000,
    //     memory_snapshot: None,
    // };
    //
    // let recording = pmat::services::dap::recording::Recording::new("test", vec![]);
    // recording.add_snapshot(snapshot);
    // let bytes = recording.to_bytes().unwrap();
    //
    // // Parse snapshot count from bytes (after header + metadata)
    // // Should be 1

    assert!(true, "Recording with 1 snapshot must serialize correctly");
}

// RED Test 7: Corrupted magic header detection
#[test]
fn test_reject_invalid_magic_header() {
    // This test drives error handling for corrupted files
    // Expected: Reading a file with wrong magic header returns error

    let invalid_data = b"XMAT\x01metadata...";

    // Will implement in GREEN phase:
    // let result = pmat::services::dap::recording::Recording::from_bytes(invalid_data);
    // assert!(result.is_err(), "Must reject invalid magic header");
    //
    // let err = result.unwrap_err();
    // assert!(err.to_string().contains("magic header"), "Error should mention magic header");

    assert_eq!(&invalid_data[0..4], b"XMAT", "Test data has invalid header");
}

// RED Test 8: Version mismatch detection
#[test]
fn test_reject_unsupported_version() {
    // This test drives forward compatibility checks
    // Expected: Reading a file with version > CURRENT_VERSION returns error

    let future_version = 99u8;

    // Will implement in GREEN phase:
    // let data = create_test_file_with_version(future_version);
    // let result = pmat::services::dap::recording::Recording::from_bytes(&data);
    // assert!(result.is_err(), "Must reject future versions");
    //
    // let err = result.unwrap_err();
    // assert!(err.to_string().contains("version"), "Error should mention version");

    assert!(future_version > 1, "Test uses future version");
}

// RED Test 9: MessagePack encoding validation
#[test]
fn test_messagepack_encoding() {
    // This test drives the choice of MessagePack as serialization format
    // Expected: Metadata and snapshots are encoded using MessagePack (rmp-serde)

    // Will implement in GREEN phase:
    // use rmp_serde::{Serializer, Deserializer};
    //
    // let metadata = RecordingMetadata { ... };
    // let mut buf = Vec::new();
    // metadata.serialize(&mut Serializer::new(&mut buf)).unwrap();
    //
    // // Verify MessagePack magic bytes (first byte indicates fixmap/fixarray/etc)
    // assert!(!buf.is_empty(), "MessagePack should produce bytes");

    assert!(
        true,
        "Must use MessagePack for metadata and snapshot encoding"
    );
}

// RED Test 10: Snapshot count validation
#[test]
fn test_snapshot_count_matches_array_length() {
    // This test drives consistency validation
    // Expected: Declared snapshot count must match actual snapshot array length

    // Will implement in GREEN phase:
    // let recording = Recording::new(...);
    // recording.add_snapshot(...); // Add 3 snapshots
    // recording.add_snapshot(...);
    // recording.add_snapshot(...);
    //
    // let bytes = recording.to_bytes().unwrap();
    // let parsed = Recording::from_bytes(&bytes).unwrap();
    //
    // assert_eq!(parsed.snapshot_count(), 3, "Count must match array length");
    // assert_eq!(parsed.snapshots().len(), 3, "Array must have 3 elements");

    assert!(true, "Snapshot count field must match array length");
}

// RED Test 11: Large snapshot count (safety check)
#[test]
fn test_reject_unreasonable_snapshot_count() {
    // This test drives DoS protection
    // Expected: Reject files claiming billions of snapshots (likely corrupted)

    let unreasonable_count = u32::MAX; // 4 billion snapshots

    // Will implement in GREEN phase:
    // let malicious_data = create_file_with_snapshot_count(unreasonable_count);
    // let result = Recording::from_bytes(&malicious_data);
    // assert!(result.is_err(), "Must reject unreasonable snapshot counts");
    //
    // let err = result.unwrap_err();
    // assert!(err.to_string().contains("snapshot count"), "Error should mention count");

    assert!(
        unreasonable_count > 1_000_000,
        "Test uses unreasonable count"
    );
}

// RED Test 12: File format documentation
#[test]
fn test_format_specification_exists() {
    // This test drives documentation requirement
    // Expected: File format is documented in docs/specifications/

    // Will verify in GREEN phase that documentation exists:
    // let spec_path = std::path::Path::new("docs/specifications/pmat-recording-format.md");
    // assert!(spec_path.exists(), "Format specification must be documented");

    assert!(true, "Format specification must be written");
}

// RED Test 13: Roundtrip serialization (empty)
#[test]
fn test_roundtrip_empty_recording() {
    // This test drives basic serialization/deserialization
    // Expected: Serialize empty recording, deserialize, get same result

    // Will implement in GREEN phase:
    // let original = Recording::new("test_program", vec![]);
    // let bytes = original.to_bytes().unwrap();
    // let deserialized = Recording::from_bytes(&bytes).unwrap();
    //
    // assert_eq!(deserialized.metadata().program, "test_program");
    // assert_eq!(deserialized.snapshots().len(), 0);

    assert!(true, "Empty recording must roundtrip correctly");
}

// RED Test 14: Roundtrip with snapshots
#[test]
fn test_roundtrip_recording_with_snapshots() {
    // This test drives full serialization/deserialization with data
    // Expected: Serialize recording with snapshots, deserialize, verify data integrity

    // Will implement in GREEN phase:
    // let snapshot1 = Snapshot { frame_id: 1, ... };
    // let snapshot2 = Snapshot { frame_id: 2, ... };
    //
    // let mut recording = Recording::new("test_program", vec![]);
    // recording.add_snapshot(snapshot1.clone());
    // recording.add_snapshot(snapshot2.clone());
    //
    // let bytes = recording.to_bytes().unwrap();
    // let deserialized = Recording::from_bytes(&bytes).unwrap();
    //
    // assert_eq!(deserialized.snapshots().len(), 2);
    // assert_eq!(deserialized.snapshots()[0].frame_id, 1);
    // assert_eq!(deserialized.snapshots()[1].frame_id, 2);

    assert!(true, "Recording with snapshots must roundtrip correctly");
}

// RED Test 15: Truncated file detection
#[test]
fn test_reject_truncated_file() {
    // This test drives robustness for incomplete files
    // Expected: Detect and reject files that are cut off mid-stream

    // Will implement in GREEN phase:
    // let valid_bytes = create_valid_recording_bytes();
    // let truncated = &valid_bytes[0..valid_bytes.len() / 2]; // Cut in half
    //
    // let result = Recording::from_bytes(truncated);
    // assert!(result.is_err(), "Must detect truncated files");
    //
    // let err = result.unwrap_err();
    // assert!(
    //     err.to_string().contains("truncated") || err.to_string().contains("unexpected end"),
    //     "Error should indicate file is incomplete"
    // );

    assert!(true, "Truncated files must be detected and rejected");
}

/// Helper: Documents expected file format structure
///
/// ```text
/// .pmat File Format (MessagePack binary):
///
/// Offset  | Type          | Description
/// --------|---------------|----------------------------------
/// 0-3     | [u8; 4]       | Magic header: b"PMAT"
/// 4       | u8            | Format version (current: 1)
/// 5-?     | MessagePack   | RecordingMetadata struct
/// ?       | u32           | Snapshot count (little-endian)
/// ?-EOF   | MessagePack   | Array of Snapshot structs
/// ```
#[test]
fn test_format_layout_documented() {
    // This test exists to document the expected format in code
    assert_eq!(4, "PMAT".len(), "Magic header is 4 bytes");
    assert_eq!(1, std::mem::size_of::<u8>(), "Version is 1 byte");
    assert_eq!(4, std::mem::size_of::<u32>(), "Snapshot count is 4 bytes");
}
