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//! FIFF format constants.
//!
//! All names mirror [`mne/_fiff/constants.py`][mne-src] exactly so that the
//! Rust code can be cross-referenced with MNE line-by-line.
//!
//! The FIFF format is a self-describing binary file format used by Elekta /
//! Neuromag MEG and EEG systems and adopted by MNE-Python as its primary I/O
//! format. Every piece of data in a FIF file is wrapped in a **tag** — a
//! 16-byte header (`kind`, `type`, `size`, `next`) followed by a payload.
//! Tags are grouped into **blocks** by `FIFF_BLOCK_START` / `FIFF_BLOCK_END`
//! sentinel tags, forming a tree.
//!
//! [mne-src]: https://github.com/mne-tools/mne-python/blob/main/mne/_fiff/constants.py
// ── Block kinds ───────────────────────────────────────────────────────────
//
// A block is opened by a FIFF_BLOCK_START tag whose i32 payload is the block
// kind, and closed by a matching FIFF_BLOCK_END tag.
/// Root / top-level block (rarely used explicitly).
pub const FIFFB_ROOT: i32 = 999;
/// Measurement block — top-level container for one recording.
pub const FIFFB_MEAS: i32 = 100;
/// Measurement-info block — channel metadata, sfreq, bad channels, etc.
pub const FIFFB_MEAS_INFO: i32 = 101;
/// Raw (continuous) data block.
pub const FIFFB_RAW_DATA: i32 = 102;
/// Processed data block.
pub const FIFFB_PROCESSED_DATA: i32 = 103;
/// Evoked / averaged data block.
pub const FIFFB_EVOKED: i32 = 104;
/// Continuous data block (alias used by some acquisition systems).
pub const FIFFB_CONTINUOUS_DATA: i32 = 112;
/// IAS (internal active shielding) raw data block.
pub const FIFFB_IAS_RAW_DATA: i32 = 119;
/// SSP projector block.
pub const FIFFB_PROJ: i32 = 313;
/// One SSP projector item block.
pub const FIFFB_PROJ_ITEM: i32 = 314;
/// MNE-specific extension block.
pub const FIFFB_MNE: i32 = 350;
/// MNE epochs block.
pub const FIFFB_MNE_EPOCHS: i32 = 373;
// ── Tag kinds — structural ─────────────────────────────────────────────────
/// Unique file identifier (first tag in every FIF file).
pub const FIFF_FILE_ID: i32 = 100;
/// Pointer to the embedded tag directory (second tag, payload = byte offset).
pub const FIFF_DIR_POINTER: i32 = 101;
/// Block identifier payload (inside `FIFF_BLOCK_START`).
pub const FIFF_BLOCK_ID: i32 = 103;
/// Opens a new block; payload = block kind (i32).
pub const FIFF_BLOCK_START: i32 = 104;
/// Closes the most recently opened block.
pub const FIFF_BLOCK_END: i32 = 105;
/// Parent block identifier.
pub const FIFF_PARENT_BLOCK_ID: i32 = 110;
// ── Tag kinds — measurement info ──────────────────────────────────────────
/// Number of channels (i32).
pub const FIFF_NCHAN: i32 = 200;
/// Sampling frequency in Hz (f32).
pub const FIFF_SFREQ: i32 = 201;
/// Channel info struct (one per channel; see [`super::info::ChannelInfo`]).
pub const FIFF_CH_INFO: i32 = 203;
/// Measurement date (Julian day, i32).
pub const FIFF_MEAS_DATE: i32 = 204;
/// Free-text comment / description (string).
pub const FIFF_COMMENT: i32 = 206;
/// Index of the first sample in acquisition time (i32).
pub const FIFF_FIRST_SAMPLE: i32 = 208;
/// Index of the last sample in acquisition time (i32).
pub const FIFF_LAST_SAMPLE: i32 = 209;
/// Online lowpass cutoff in Hz (f32); may be NaN if not set.
pub const FIFF_LOWPASS: i32 = 219;
/// Colon-separated list of bad channel names (string).
pub const FIFF_BAD_CHS: i32 = 220;
/// Online highpass cutoff in Hz (f32); may be NaN if not set.
pub const FIFF_HIGHPASS: i32 = 223;
/// Power-line frequency in Hz (f32).
pub const FIFF_LINE_FREQ: i32 = 235;
/// Experimenter name (string).
pub const FIFF_EXPERIMENTER: i32 = 212;
/// Recording description — alias for `FIFF_COMMENT`.
pub const FIFF_DESCRIPTION: i32 = FIFF_COMMENT;
// ── Tag kinds — data buffers ───────────────────────────────────────────────
/// One buffer of raw signal samples (interleaved `[n_samp, n_chan]`,
/// big-endian, type = `FIFFT_FLOAT` or `FIFFT_DOUBLE` or `FIFFT_SHORT`).
pub const FIFF_DATA_BUFFER: i32 = 300;
/// Skip `n` complete buffers (inter-buffer gap; payload = n as i32).
pub const FIFF_DATA_SKIP: i32 = 301;
/// Skip `n` individual samples (rarely used).
pub const FIFF_DATA_SKIP_SAMP: i32 = 303;
// ── Tag kinds — multi-file references ─────────────────────────────────────
/// File identifier of a referenced file.
pub const FIFF_REF_FILE_ID: i32 = 116;
/// Sequence number of a referenced file.
pub const FIFF_REF_FILE_NUM: i32 = 117;
/// Name of a referenced file.
pub const FIFF_REF_FILE_NAME: i32 = 118;
/// Role of a referenced file.
pub const FIFF_REF_ROLE: i32 = 115;
/// `FIFF_REF_ROLE` value indicating the next file in a split recording.
pub const FIFFV_ROLE_NEXT_FILE: i32 = 2;
// ── Tag payload types (the `type` field of a tag header) ──────────────────
/// Void / no payload.
pub const FIFFT_VOID: u32 = 0;
/// Unsigned 8-bit byte.
pub const FIFFT_BYTE: u32 = 1;
/// Big-endian signed 16-bit integer.
pub const FIFFT_SHORT: u32 = 2;
/// Big-endian signed 32-bit integer.
pub const FIFFT_INT: u32 = 3;
/// Big-endian IEEE 754 single-precision float (4 bytes).
pub const FIFFT_FLOAT: u32 = 4;
/// Big-endian IEEE 754 double-precision float (8 bytes).
pub const FIFFT_DOUBLE: u32 = 5;
/// Julian date (i32).
pub const FIFFT_JULIAN: u32 = 6;
/// Big-endian unsigned 16-bit integer.
pub const FIFFT_USHORT: u32 = 7;
/// Big-endian unsigned 32-bit integer.
pub const FIFFT_UINT: u32 = 8;
/// Latin-1 (ISO 8859-1) string, **not** NUL-terminated.
pub const FIFFT_STRING: u32 = 10;
/// 16-bit DAU packed sample (same wire width as `FIFFT_SHORT`).
pub const FIFFT_DAU_PACK16: u32 = 16;
/// Complex single-precision (real f32 + imag f32, 8 bytes).
pub const FIFFT_COMPLEX_FLOAT: u32 = 20;
/// Complex double-precision (real f64 + imag f64, 16 bytes).
pub const FIFFT_COMPLEX_DOUBLE: u32 = 21;
/// Legacy packed format (obsolete).
pub const FIFFT_OLD_PACK: u32 = 23;
/// 96-byte channel info struct (see [`super::info::ChannelInfo`]).
pub const FIFFT_CH_INFO_STRUCT: u32 = 30;
/// File-ID struct.
pub const FIFFT_ID_STRUCT: u32 = 31;
/// Tag-directory entry struct (16 bytes per entry).
pub const FIFFT_DIR_ENTRY_STRUCT: u32 = 32;
/// Digitisation point struct.
pub const FIFFT_DIG_POINT_STRUCT: u32 = 33;
/// Coordinate transform struct.
pub const FIFFT_COORD_TRANS_STRUCT: u32 = 35;
/// Matrix modifier — OR this with an element type to indicate a matrix payload.
pub const FIFFT_MATRIX: u32 = 0x4000_0000;
// ── `next` field sentinels in a tag header ────────────────────────────────
/// The next tag follows immediately: `next_pos = pos + 16 + size`.
pub const FIFFV_NEXT_SEQ: i32 = 0;
/// There is no next tag (end of sequence / block).
pub const FIFFV_NEXT_NONE: i32 = -1;
// ── Channel kind codes (`ChannelInfo::kind`) ──────────────────────────────
/// MEG magnetometer or gradiometer channel.
pub const FIFFV_MEG_CH: i32 = 1;
/// EEG scalp-potential channel.
pub const FIFFV_EEG_CH: i32 = 2;
/// Stimulus / trigger channel.
pub const FIFFV_STIM_CH: i32 = 3;
/// Electro-oculogram channel.
pub const FIFFV_EOG_CH: i32 = 202;
/// Electromyogram channel.
pub const FIFFV_EMG_CH: i32 = 302;
/// Electrocardiogram channel.
pub const FIFFV_ECG_CH: i32 = 402;
/// Miscellaneous auxiliary channel.
pub const FIFFV_MISC_CH: i32 = 502;
/// MEG reference (compensation) channel.
pub const FIFFV_REF_MEG_CH: i32 = 301;
/// Stereo-EEG depth electrode channel.
pub const FIFFV_SEEG_CH: i32 = 802;
/// Electrocorticography (ECoG) channel.
pub const FIFFV_ECOG_CH: i32 = 902;
// ── Helpers ───────────────────────────────────────────────────────────────
/// Return the number of bytes occupied by one sample of the given tag type.
///
/// Returns `None` for types that do not represent scalar numeric samples
/// (e.g. strings, structs).
///
/// # Examples
///
/// ```
/// use exg::fiff::constants::{bytes_per_sample, FIFFT_FLOAT, FIFFT_DOUBLE, FIFFT_SHORT};
/// assert_eq!(bytes_per_sample(FIFFT_FLOAT), Some(4));
/// assert_eq!(bytes_per_sample(FIFFT_DOUBLE), Some(8));
/// assert_eq!(bytes_per_sample(FIFFT_SHORT), Some(2));
/// assert_eq!(bytes_per_sample(99), None);
/// ```