//! TRACES: FR-RAW-2
//! A second decoder behind the trait, and the callers none the wiser.
//!
//! FR-RAW-2 says a decoder may be added for broader camera coverage without
//! changing callers (D2: LibRaw, for bodies rawler lacks). These tests are
//! that claim, made checkable: [`Stub`] reads a container no real decoder
//! knows, and the catalog scan, the preview ladder and export are each handed
//! it through the same `&dyn Decoder` the application passes rawler through.
//!
//! Every assertion is on something only the stub could have produced — a
//! camera name, a preview size, a header budget, a turn — so a caller that
//! reached past the trait to `dr_decode::metadata` or its siblings would get
//! rawler's refusal of these bytes and fail here, rather than pass on a real
//! file where the two decoders happen to agree.

use std::sync::Mutex;

use dr_decode::{
    BaseCurve, CfaPattern, CropRect, DecodeError, Decoder, Metadata, Preview, PreviewLocation,
    PreviewSize, RawImage,
};
use dr_types::Orientation;

/// What every stub file starts with. Not a signature any real format uses.
const MAGIC: &[u8] = b"STUB-RAW";

/// The stub's header budget: far smaller than `dr_decode::HEADER_BYTES`, so a
/// caller that fetched the shipped decoder's budget instead is visible.
const HEADER: u64 = 64;

/// The size of the preview [`Decoder::preview`] cuts, before orientation.
const PREVIEW: (u32, u32) = (24, 12);

/// The size of the JPEG embedded for the remote ladder, before orientation.
const EMBEDDED: (u32, u32) = (40, 20);

/// The sensor [`Decoder::decode`] returns.
const SENSOR: (u32, u32) = (32, 16);

/// EXIF 6: one clockwise quarter turn, so every size above comes out swapped.
fn turned() -> Orientation {
    Orientation::from_exif(6)
}

/// A decoder for the stub container, recording the length of every header it
/// is handed so a test can see how much the caller fetched.
#[derive(Debug, Default)]
struct Stub {
    headers: Mutex<Vec<usize>>,
}

impl Stub {
    fn is_ours(bytes: &[u8]) -> bool {
        bytes.starts_with(MAGIC)
    }

    fn refuse() -> DecodeError {
        DecodeError::Unsupported("not a stub file".into())
    }
}

impl Decoder for Stub {
    fn header_bytes(&self) -> u64 {
        HEADER
    }

    fn metadata(&self, bytes: &[u8]) -> Result<Metadata, DecodeError> {
        self.headers.lock().unwrap().push(bytes.len());
        if !Self::is_ours(bytes) {
            return Err(Self::refuse());
        }
        Ok(Metadata {
            make: Some("Stubco".into()),
            model: Some("Stubco One".into()),
            iso: Some(321),
            captured_at: Some(1_234_567_890),
            orientation: Some(turned()),
            ..Default::default()
        })
    }

    fn orientation(&self, header: &[u8]) -> Option<Orientation> {
        Self::is_ours(header).then(turned)
    }

    fn locate_preview(&self, header: &[u8], file_len: u64) -> Option<PreviewLocation> {
        if !Self::is_ours(header) {
            return None;
        }
        let word = |at: usize| u32::from_le_bytes(header[at..at + 4].try_into().unwrap()) as u64;
        let (start, len) = (word(8), word(12));
        (start + len <= file_len).then_some(PreviewLocation {
            range: start..start + len,
            width: Some(EMBEDDED.0),
            height: Some(EMBEDDED.1),
        })
    }

    fn preview(&self, bytes: &[u8], _size: PreviewSize) -> Result<Preview, DecodeError> {
        if !Self::is_ours(bytes) {
            return Err(Self::refuse());
        }
        Ok(Preview {
            width: PREVIEW.0,
            height: PREVIEW.1,
            rgba: vec![200; (PREVIEW.0 * PREVIEW.1 * 4) as usize],
        })
    }

    fn decode(&self, bytes: &[u8]) -> Result<RawImage, DecodeError> {
        if !Self::is_ours(bytes) {
            return Err(Self::refuse());
        }
        let (width, height) = SENSOR;
        Ok(RawImage {
            width,
            height,
            data: vec![2048; (width * height) as usize],
            cfa_pattern: CfaPattern::Rggb,
            black_level: [0; 4],
            white_level: 4095,
            wb_coeffs: [1.0; 4],
            color_matrix: None,
            base_curve: BaseCurve::IDENTITY,
            crop: CropRect {
                x: 0,
                y: 0,
                width,
                height,
            },
            samples_per_pixel: 1,
            profile: None,
            make: "Stubco".into(),
            model: "Stubco One".into(),
        })
    }
}

/// A stub file: the magic, where the embedded JPEG sits, padding to the
/// header budget, then the JPEG — kept well past [`HEADER`] so a header read
/// and a whole-file read differ in length.
fn stub_file() -> Vec<u8> {
    let (w, h) = EMBEDDED;
    let jpeg = dr_thumbs::encode_rgba(w, h, &vec![90; (w * h * 4) as usize]).expect("encodes");
    let mut file = MAGIC.to_vec();
    file.extend_from_slice(&(HEADER as u32).to_le_bytes());
    file.extend_from_slice(&(jpeg.len() as u32).to_le_bytes());
    file.resize(HEADER as usize, 0);
    file.extend_from_slice(&jpeg);
    file
}

const NAME: &str = "IMG_0001.STB";

/// The stub file in a folder of its own, served by the folder backend — the
/// same `RemoteBackend` the scan and the ladder use against a real library.
/// `tag` keeps two tests running at once out of each other's folder.
fn library(tag: &str) -> (std::path::PathBuf, dr_sync_folder::FolderBackend, u64) {
    let dir = std::env::temp_dir().join(format!("dr-decoder-seam-{tag}-{}", std::process::id()));
    std::fs::create_dir_all(&dir).unwrap();
    let file = stub_file();
    std::fs::write(dir.join(NAME), &file).unwrap();
    let backend = dr_sync_folder::FolderBackend::new(&dir).expect("folder opens");
    (dir, backend, file.len() as u64)
}

fn request(size: u64) -> crate::library::ThumbnailRequest {
    crate::library::ThumbnailRequest {
        row: 0,
        path: NAME.into(),
        file_id: Some(1),
        size,
        image_id: 7,
        thumb_size: dr_thumbs::ThumbSize::Grid,
        needs_metadata: true,
        full_resolution: false,
    }
}

fn swapped((w, h): (u32, u32)) -> (u32, u32) {
    (h, w)
}

/// TRACES: FR-RAW-2 | FR-CAT-5
/// The catalog scan dates an image through the decoder it is given, and
/// fetches the header that decoder asked for rather than the shipped one's.
#[test]
fn the_catalog_scan_reads_headers_through_the_trait() {
    let (dir, backend, size) = library("scan");
    let stub = Stub::default();
    let mut found = Vec::new();

    let rt = crate::net_runtime::build().unwrap();
    let reached = rt.block_on(crate::library::read_metadata_only(
        &backend,
        &stub,
        &request(size),
        &mut found,
    ));

    assert!(reached);
    assert_eq!(found.len(), 1, "the stub's header was read");
    assert_eq!(found[0].image_id, 7);
    assert_eq!(found[0].camera.as_deref(), Some("Stubco One"));
    assert_eq!(found[0].captured_at, Some(1_234_567_890));
    assert_eq!(found[0].iso, Some(321));
    assert_eq!(
        *stub.headers.lock().unwrap(),
        vec![HEADER as usize],
        "one header, of the size the decoder declared"
    );
    let _ = std::fs::remove_dir_all(dir);
}

/// TRACES: FR-RAW-2 | FR-CULL-2 | FR-NC-3
/// Every rung of the preview ladder takes its preview and its orientation
/// from the decoder it is given: the remote two-stage fetch, the import's
/// thumbnail, and the viewer's fallback when there is no GPU.
#[test]
fn the_preview_ladder_cuts_previews_through_the_trait() {
    let (dir, backend, size) = library("ladder");
    let stub = Stub::default();
    let bytes = stub_file();

    // Remote: header, locate, fetch the range, decode, turn.
    let rt = crate::net_runtime::build().unwrap();
    let mut found = Vec::new();
    let outcome = rt.block_on(crate::library::fetch_preview(
        &backend,
        &stub,
        &request(size),
        &mut found,
    ));
    match outcome {
        crate::library::PreviewOutcome::Ready(p) => {
            assert_eq!((p.width, p.height), swapped(EMBEDDED))
        }
        crate::library::PreviewOutcome::Unavailable(r)
        | crate::library::PreviewOutcome::Offline(r) => panic!("no preview: {r}"),
    }
    assert_eq!(found.len(), 1, "the same header dated the image");

    // An import's thumbnail, from bytes already in hand.
    let thumb = crate::import::make_thumbnail(&stub, &bytes).expect("a thumbnail");
    assert_eq!((thumb.width, thumb.height), swapped(PREVIEW));

    // The viewer with no GPU, which shows the embedded preview read-only.
    let loaded = crate::load_bytes(None, &stub, &bytes).expect("a preview to show");
    assert!(loaded.session.is_none());
    assert_eq!((loaded.width, loaded.height), swapped(PREVIEW));
    assert_eq!(loaded.meta.model.as_deref(), Some("Stubco One"));

    let _ = std::fs::remove_dir_all(dir);
}

/// TRACES: FR-RAW-2 | FR-EXP-8 | FR-EXP-9
/// Export opens a photograph for its full-size render through the decoder it
/// is given: the header it carries and the sensor it renders are the stub's.
#[test]
fn export_decodes_through_the_trait() {
    let Some(gpu) = crate::develop::test_support::headless() else {
        eprintln!("no GPU adapter; skipping");
        return;
    };
    let stub = Stub::default();

    let (meta, session) =
        crate::export::open_for_export(&gpu, &stub, &stub_file()).expect("the stub opens");

    assert_eq!(meta.make.as_deref(), Some("Stubco"));
    assert_eq!(
        session.source_metadata().and_then(|m| m.model.as_deref()),
        Some("Stubco One"),
        "the session remembers the header it was opened from"
    );
    assert_eq!(session.source_size(), swapped(SENSOR));
}