//! Per-map atlases and the `.ppda` (PaPerDollAtlas) consumer manifest
//! (Tim t955u/t957u).
//!
//! After every loose target PNG of a run is published and checksum-verified,
//! production writes one atlas per map type (`<sex>-<settype>-<map>-atlas.png`)
//! and a strict JSON `.ppda` (`<sex>-<settype>-atlas.ppda`) next to them in the
//! run directory. Cells are exactly the target resolution, without padding or
//! scaling. One row per (clip, frame) in source clip order and frame order;
//! columns are pitch (−60→+60) × yaw (0→330). All four atlases share identical
//! cell coordinates. Atlases are streamed band by band (one cell row at a time),
//! published atomically without clobbering, and the `.ppda` is written last.
//!
//! [`AtlasSet`] is the validating consumer reader used by the 2D preview.
use crate::{
    digest::{self, is_sha256_hex, Sha256},
    export_set::{self, ExportError, MapImage, MapKind, MAX_PNG_BYTES, MAX_TARGET},
    preview::PRODUCTION_PITCHES,
    production::{self, Plan, FAR, NEAR},
    project::CameraFraming,
};
use serde::{Deserialize, Serialize};
use std::{
    collections::BTreeMap,
    fs,
    io::Write,
    path::{Path, PathBuf},
    sync::atomic::{AtomicBool, Ordering},
};

/// `.ppda` schema version written and accepted.
pub const PPDA_FORMAT_VERSION: u32 = 1;
/// Largest atlas side in pixels (common GPU texture limit). Larger exports are
/// refused up front with a clear message; atlases are never split.
pub const MAX_ATLAS_DIM: u32 = 16384;
/// Bounded `.ppda` size on read.
pub const MAX_PPDA_BYTES: u64 = 64 * 1024 * 1024;
/// Bounded encoded atlas PNG size on read.
pub const MAX_ATLAS_PNG_BYTES: u64 = 4 * 1024 * 1024 * 1024;
/// Decoded-memory budget for one loaded atlas set (four maps) in the preview.
pub const MAX_DECODED_SET_BYTES: u64 = 2 * 1024 * 1024 * 1024;
/// Map order inside the `.ppda` and atlas production.
pub const ATLAS_MAPS: [MapKind; 4] = [
    MapKind::Diffuse,
    MapKind::Normal,
    MapKind::Depth,
    MapKind::Specular,
];
const MAX_CLIPS: usize = 4096;
const MAX_CLIP_NAME: usize = 256;

pub fn atlas_png_name(sex: &str, set: &str, kind: MapKind) -> String {
    format!("{sex}-{set}-{}-atlas.png", kind.token())
}

pub fn ppda_name(sex: &str, set: &str) -> String {
    format!("{sex}-{set}-atlas.ppda")
}

/// Deterministic grid shared by all four atlases of one export.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct AtlasLayout {
    pub cell_width: u32,
    pub cell_height: u32,
    pub columns: u32,
    pub rows: u32,
    pub width: u32,
    pub height: u32,
}

impl AtlasLayout {
    pub fn new(cell_width: u32, cell_height: u32, rows: u32) -> Result<Self, String> {
        if cell_width == 0
            || cell_height == 0
            || cell_width > MAX_TARGET
            || cell_height > MAX_TARGET
        {
            return Err("atlascel moet 1–256 pixels per as zijn".into());
        }
        if rows == 0 {
            return Err("atlas zonder rijen".into());
        }
        let columns = (PRODUCTION_PITCHES.len() * production::production_yaws().len()) as u32;
        let width = u64::from(columns) * u64::from(cell_width);
        let height = u64::from(rows) * u64::from(cell_height);
        if width > u64::from(MAX_ATLAS_DIM) || height > u64::from(MAX_ATLAS_DIM) {
            return Err(format!(
                "atlas zou {width}×{height} pixels worden ({columns} hoeken × {rows} frames); \
                 maximaal {MAX_ATLAS_DIM}×{MAX_ATLAS_DIM}. Verlaag fps, targetresolutie of \
                 animatieduur — de atlas wordt niet gesplitst"
            ));
        }
        Ok(Self {
            cell_width,
            cell_height,
            columns,
            rows,
            width: width as u32,
            height: height as u32,
        })
    }

    pub fn for_plan(plan: &Plan, cell_width: u32, cell_height: u32) -> Result<Self, String> {
        let rows = plan
            .clips
            .iter()
            .try_fold(0u32, |n, c| n.checked_add(c.frames))
            .ok_or("te veel frames voor de atlas")?;
        Self::new(cell_width, cell_height, rows)
    }

    /// Column of (pitch, yaw): pitch-major, then yaw.
    pub fn column(pitch: i32, yaw: u32) -> Option<u32> {
        let p = PRODUCTION_PITCHES.iter().position(|x| *x == pitch)?;
        let y = production::production_yaws()
            .iter()
            .position(|x| *x == yaw)?;
        Some((p * production::production_yaws().len() + y) as u32)
    }

    pub fn cell(&self, row: u32, column: u32) -> PpdaView {
        let yaws = production::production_yaws();
        let pitch = PRODUCTION_PITCHES[column as usize / yaws.len()];
        let yaw = yaws[column as usize % yaws.len()];
        PpdaView {
            pitch,
            yaw,
            x: column * self.cell_width,
            y: row * self.cell_height,
            w: self.cell_width,
            h: self.cell_height,
        }
    }
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct Ppda {
    pub format_version: u32,
    pub sex: String,
    pub settype: String,
    pub project: PpdaProject,
    /// Export/camera contract so body and equipment atlases can be checked for
    /// compatibility without the loose run manifests.
    pub identity: PpdaIdentity,
    pub fps: u32,
    pub cell_width: u32,
    pub cell_height: u32,
    pub pitches: Vec<i32>,
    pub yaws: Vec<u32>,
    pub maps: BTreeMap<String, PpdaMap>,
    pub clips: Vec<PpdaClip>,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct PpdaProject {
    pub id: String,
    pub name: String,
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct PpdaIdentity {
    pub body_model_sha256: String,
    pub equipment_preset_sha256: Option<String>,
    pub framing: CameraFraming,
    pub pivot_source: String,
    pub near: f32,
    pub far: f32,
    pub camera_distance: f32,
    pub normal_space: String,
    pub depth: String,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct PpdaMap {
    pub file: String,
    pub sha256: String,
    pub width: u32,
    pub height: u32,
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct PpdaClip {
    pub source_index: u32,
    pub name: String,
    pub token: String,
    pub frame_count: u32,
    pub duration: f32,
    pub frames: Vec<PpdaFrame>,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct PpdaFrame {
    pub index: u32,
    pub views: Vec<PpdaView>,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct PpdaView {
    pub pitch: i32,
    pub yaw: u32,
    pub x: u32,
    pub y: u32,
    pub w: u32,
    pub h: u32,
}

/// What production records in `complete.json` after writing the atlases.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct AtlasOutput {
    pub ppda: String,
    pub ppda_sha256: String,
    /// map token → (file name, sha256)
    pub maps: BTreeMap<String, (String, String)>,
}

impl AtlasOutput {
    pub fn to_json(&self) -> serde_json::Value {
        let maps: serde_json::Map<String, serde_json::Value> = self
            .maps
            .iter()
            .map(|(k, (file, sha))| (k.clone(), serde_json::json!({"file": file, "sha256": sha})))
            .collect();
        serde_json::json!({
            "ppda": self.ppda,
            "ppda_sha256": self.ppda_sha256,
            "maps": maps,
        })
    }
}

struct HashingWriter<W: Write> {
    inner: W,
    hasher: Sha256,
}

impl<W: Write> Write for HashingWriter<W> {
    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
        let n = self.inner.write(buf)?;
        self.hasher.update(&buf[..n]);
        Ok(n)
    }
    fn flush(&mut self) -> std::io::Result<()> {
        self.inner.flush()
    }
}

/// Inputs for writing the atlases of one completed run.
pub struct AtlasJob<'a> {
    pub root: &'a Path,
    pub render_doc: &'a serde_json::Value,
    pub plan: &'a Plan,
    pub sex: &'a str,
    pub set: &'a str,
    pub cell_width: u32,
    pub cell_height: u32,
    /// Relative loose PNG path → verified SHA-256 (every planned file).
    pub png_sha256: &'a BTreeMap<String, String>,
    /// Resume attempt number for quarantine names of stale atlas files.
    pub attempt: u32,
    pub cancel: &'a AtomicBool,
}

fn rows_of(plan: &Plan) -> Vec<(usize, u32)> {
    plan.clips
        .iter()
        .enumerate()
        .flat_map(|(c, clip)| (0..clip.frames).map(move |f| (c, f)))
        .collect()
}

/// Load one verified loose cell as raw 4-byte-per-pixel rows (RGBA8 or
/// big-endian gray16+alpha16, matching the atlas PNG sample layout).
fn load_cell(
    job: &AtlasJob<'_>,
    clip: &str,
    frame: u32,
    pitch: i32,
    yaw: u32,
    kind: MapKind,
) -> Result<Vec<u8>, String> {
    let rel = production::output_path(job.sex, job.set, clip, frame, pitch, yaw, kind.token())?;
    let rel = rel.to_str().ok_or("ongeldig PNG-pad")?.replace('\\', "/");
    let expected = job
        .png_sha256
        .get(&rel)
        .ok_or_else(|| format!("atlas: {rel} ontbreekt in de checksums"))?;
    let path = job.root.join(&rel);
    export_set::verify_regular_file(&path, job.root).map_err(|e| e.to_string())?;
    let bytes = export_set::read_bounded_file(&path, MAX_PNG_BYTES).map_err(|e| e.to_string())?;
    if digest::sha256_hex(&bytes) != *expected {
        return Err(format!("atlas: checksum van {rel} klopt niet meer"));
    }
    match export_set::decode_map(&bytes, kind, job.cell_width, job.cell_height)
        .map_err(|e| format!("atlas: {rel}: {e}"))?
    {
        MapImage::Rgba8 { rgba, .. } => Ok(rgba),
        MapImage::Depth16 { samples, .. } => {
            Ok(samples.iter().flat_map(|s| s.to_be_bytes()).collect())
        }
    }
}

/// Stream-encode one atlas PNG into `out`.
fn encode_atlas(
    job: &AtlasJob<'_>,
    layout: &AtlasLayout,
    kind: MapKind,
    out: &mut dyn Write,
    progress: &mut dyn FnMut(String),
) -> Result<(), String> {
    let mut encoder = png::Encoder::new(out, layout.width, layout.height);
    if kind == MapKind::Depth {
        encoder.set_color(png::ColorType::GrayscaleAlpha);
        encoder.set_depth(png::BitDepth::Sixteen);
    } else {
        encoder.set_color(png::ColorType::Rgba);
        encoder.set_depth(png::BitDepth::Eight);
        if kind == MapKind::Diffuse {
            encoder.set_source_srgb(png::SrgbRenderingIntent::Perceptual);
        }
    }
    let mut writer = encoder.write_header().map_err(|e| e.to_string())?;
    let row_bytes = layout.width as usize * 4;
    let cell_row_bytes = layout.cell_width as usize * 4;
    let mut stream = writer
        .stream_writer_with_size(row_bytes.max(4096))
        .map_err(|e| e.to_string())?;
    let rows = rows_of(job.plan);
    let total = rows.len();
    let mut band = vec![0u8; row_bytes * layout.cell_height as usize];
    for (row, (clip, frame)) in rows.into_iter().enumerate() {
        if job.cancel.load(Ordering::Relaxed) {
            return Err("geannuleerd".into());
        }
        if row % 8 == 0 {
            progress(format!(
                "atlas {} · rij {}/{}",
                kind.token(),
                row + 1,
                total
            ));
        }
        let token = &job.plan.clips[clip].token;
        for column in 0..layout.columns {
            let view = layout.cell(0, column);
            let cell = load_cell(job, token, frame, view.pitch, view.yaw, kind)?;
            for y in 0..layout.cell_height as usize {
                let dst = y * row_bytes + view.x as usize * 4;
                band[dst..dst + cell_row_bytes]
                    .copy_from_slice(&cell[y * cell_row_bytes..(y + 1) * cell_row_bytes]);
            }
        }
        stream.write_all(&band).map_err(|e| e.to_string())?;
    }
    stream.finish().map_err(|e| e.to_string())?;
    writer.finish().map_err(|e| e.to_string())?;
    Ok(())
}

/// Publish `name` in the run root without clobbering. When a file already
/// exists (crash after publication during an earlier attempt) it is kept when
/// byte-identical to the regenerated output, otherwise moved aside.
fn publish_streamed(
    root: &Path,
    name: &str,
    attempt: u32,
    mut encode: impl FnMut(&mut dyn Write) -> Result<(), String>,
) -> Result<String, String> {
    let path = root.join(name);
    if fs::symlink_metadata(&path).is_ok() {
        let mut sink = HashingWriter {
            inner: std::io::sink(),
            hasher: Sha256::new(),
        };
        encode(&mut sink)?;
        let fresh = digest::hex(&sink.hasher.finalize());
        let regular = fs::symlink_metadata(&path)
            .map(|m| m.file_type().is_file())
            .unwrap_or(false);
        if regular
            && digest::sha256_file(&path, MAX_ATLAS_PNG_BYTES)
                .ok()
                .as_deref()
                == Some(fresh.as_str())
        {
            return Ok(fresh);
        }
        crate::resume::quarantine(root, name, attempt)?;
    }
    let mut digest_out = None;
    production::atomic_file(root, Path::new(name), |file| {
        let mut writer = HashingWriter {
            inner: std::io::BufWriter::new(file),
            hasher: Sha256::new(),
        };
        encode(&mut writer)?;
        writer.flush().map_err(|e| e.to_string())?;
        digest_out = Some(digest::hex(&writer.hasher.finalize()));
        Ok(())
    })?;
    digest_out.ok_or_else(|| "atlas-digest ontbreekt".into())
}

/// Build the `.ppda` document for a plan/contract (pure; no disk access).
pub fn build_ppda(
    render_doc: &serde_json::Value,
    plan: &Plan,
    layout: &AtlasLayout,
    sex: &str,
    set: &str,
    map_digests: &BTreeMap<String, String>,
) -> Result<Ppda, String> {
    let get = |p: &str| render_doc.pointer(p).ok_or(format!("render.json mist {p}"));
    let text = |p: &str| -> Result<String, String> {
        get(p)?
            .as_str()
            .map(str::to_string)
            .ok_or(format!("{p} is geen tekst"))
    };
    let framing: CameraFraming =
        serde_json::from_value(get("/framing")?.clone()).map_err(|e| e.to_string())?;
    let fps = get("/fps")?.as_u64().ok_or("fps")? as u32;
    let mut maps = BTreeMap::new();
    for kind in ATLAS_MAPS {
        maps.insert(
            kind.token().to_string(),
            PpdaMap {
                file: atlas_png_name(sex, set, kind),
                sha256: map_digests
                    .get(kind.token())
                    .cloned()
                    .ok_or("atlas-digest ontbreekt")?,
                width: layout.width,
                height: layout.height,
            },
        );
    }
    let mut row = 0u32;
    let mut clips = Vec::with_capacity(plan.clips.len());
    for (i, clip) in plan.clips.iter().enumerate() {
        let duration = render_doc
            .pointer(&format!("/clips/{i}/duration"))
            .and_then(|d| d.as_f64())
            .unwrap_or(0.) as f32;
        let mut frames = Vec::with_capacity(clip.frames as usize);
        for index in 0..clip.frames {
            frames.push(PpdaFrame {
                index,
                views: (0..layout.columns).map(|c| layout.cell(row, c)).collect(),
            });
            row += 1;
        }
        clips.push(PpdaClip {
            source_index: i as u32,
            name: clip.source_name.clone(),
            token: clip.token.clone(),
            frame_count: clip.frames,
            duration,
            frames,
        });
    }
    Ok(Ppda {
        format_version: PPDA_FORMAT_VERSION,
        sex: sex.into(),
        settype: set.into(),
        project: PpdaProject {
            id: text("/project/id")?,
            name: text("/project/name")?,
        },
        identity: PpdaIdentity {
            body_model_sha256: text("/body_model/sha256")?,
            equipment_preset_sha256: render_doc
                .pointer("/equipment_preset/sha256")
                .and_then(|v| v.as_str())
                .map(str::to_string),
            framing,
            pivot_source: text("/pivot_source/kind")?,
            near: NEAR,
            far: FAR,
            camera_distance: 10.,
            normal_space: text("/normal_space")?,
            depth: text("/depth")?,
        },
        fps,
        cell_width: layout.cell_width,
        cell_height: layout.cell_height,
        pitches: PRODUCTION_PITCHES.to_vec(),
        yaws: production::production_yaws().to_vec(),
        maps,
        clips,
    })
}

/// Write the four atlases and the `.ppda` after all loose maps are verified.
pub fn write_atlases(
    job: &AtlasJob<'_>,
    progress: &mut dyn FnMut(String),
) -> Result<AtlasOutput, String> {
    let layout = AtlasLayout::for_plan(job.plan, job.cell_width, job.cell_height)?;
    if job.png_sha256.len() as u64 != u64::from(job.plan.files) {
        return Err("atlas: niet alle losse maps zijn geverifieerd".into());
    }
    let mut maps = BTreeMap::new();
    let mut digests = BTreeMap::new();
    for kind in ATLAS_MAPS {
        let name = atlas_png_name(job.sex, job.set, kind);
        let digest = publish_streamed(job.root, &name, job.attempt, |out| {
            encode_atlas(job, &layout, kind, out, progress)
        })?;
        digests.insert(kind.token().to_string(), digest.clone());
        maps.insert(kind.token().to_string(), (name, digest));
    }
    let ppda = build_ppda(
        job.render_doc,
        job.plan,
        &layout,
        job.sex,
        job.set,
        &digests,
    )?;
    let mut bytes = serde_json::to_vec_pretty(&ppda).map_err(|e| e.to_string())?;
    bytes.push(b'\n');
    let name = ppda_name(job.sex, job.set);
    progress(format!("atlas · {name}"));
    let ppda_sha256 = publish_streamed(job.root, &name, job.attempt, |out| {
        out.write_all(&bytes).map_err(|e| e.to_string())
    })?;
    Ok(AtlasOutput {
        ppda: name,
        ppda_sha256,
        maps,
    })
}

// ---------------------------------------------------------------- reader --

fn ident(msg: impl Into<String>) -> ExportError {
    ExportError::Identity(msg.into())
}

fn validate_ppda(p: &Ppda, file_name: &str) -> Result<AtlasLayout, ExportError> {
    if p.format_version != PPDA_FORMAT_VERSION {
        return Err(ident(format!(
            ".ppda format_version {} wordt niet ondersteund (verwacht {PPDA_FORMAT_VERSION})",
            p.format_version
        )));
    }
    if !["male", "female"].contains(&p.sex.as_str()) {
        return Err(ident(".ppda: ongeldig geslacht"));
    }
    if p.settype != "body" && !crate::equipment::valid_name(&p.settype) {
        return Err(ident(".ppda: ongeldig settype"));
    }
    if file_name != ppda_name(&p.sex, &p.settype) {
        return Err(ident(format!(
            ".ppda-bestandsnaam '{file_name}' past niet bij {}/{}",
            p.sex, p.settype
        )));
    }
    if p.project.id.is_empty() || p.project.id.len() > 128 || p.project.name.len() > 256 {
        return Err(ident(".ppda: project id/naam ongeldig"));
    }
    let id = &p.identity;
    if !is_sha256_hex(&id.body_model_sha256) {
        return Err(ExportError::Corrupt(
            ".ppda: body_model_sha256 ongeldig".into(),
        ));
    }
    match (&id.equipment_preset_sha256, p.settype == "body") {
        (None, true) => {}
        (Some(h), false) if is_sha256_hex(h) => {}
        _ => {
            return Err(ident(
                ".ppda: equipment_preset_sha256 past niet bij settype",
            ))
        }
    }
    id.framing.validate().map_err(ExportError::Identity)?;
    if !["manual", "neck", "fallback"].contains(&id.pivot_source.as_str()) {
        return Err(ident(".ppda: onbekende pivot_source"));
    }
    if id.near != NEAR || id.far != FAR || id.camera_distance != 10. {
        return Err(ident(".ppda: camera-contract wijkt af"));
    }
    if p.fps == 0 || p.fps > 240 {
        return Err(ident(".ppda: ongeldige fps"));
    }
    if p.pitches != PRODUCTION_PITCHES || p.yaws != production::production_yaws() {
        return Err(ident(".ppda: pitches/yaws wijken af van −60…+60 × 0…330"));
    }
    if p.clips.is_empty() || p.clips.len() > MAX_CLIPS {
        return Err(ExportError::Resource(
            ".ppda: clip-inventaris ongeldig".into(),
        ));
    }
    let rows = p
        .clips
        .iter()
        .try_fold(0u32, |n, c| n.checked_add(c.frame_count))
        .ok_or_else(|| ExportError::Resource(".ppda: te veel frames".into()))?;
    let layout =
        AtlasLayout::new(p.cell_width, p.cell_height, rows).map_err(ExportError::Resource)?;
    let mut tokens = std::collections::BTreeSet::new();
    let mut row = 0u32;
    for (i, clip) in p.clips.iter().enumerate() {
        if clip.source_index as usize != i {
            return Err(ident(".ppda: clips niet in bronvolgorde"));
        }
        if clip.token.is_empty()
            || clip.token.len() > 64
            || !crate::equipment::valid_name(&clip.token)
            || !tokens.insert(clip.token.clone())
        {
            return Err(ident(format!(
                ".ppda: ongeldige clip-token '{}'",
                clip.token
            )));
        }
        if clip.name.len() > MAX_CLIP_NAME || !clip.duration.is_finite() || clip.duration < 0. {
            return Err(ident(".ppda: clipnaam/duur ongeldig"));
        }
        if clip.frame_count == 0 || clip.frames.len() != clip.frame_count as usize {
            return Err(ident(".ppda: frame_count past niet bij frames"));
        }
        for (k, frame) in clip.frames.iter().enumerate() {
            if frame.index as usize != k || frame.views.len() != layout.columns as usize {
                return Err(ident(".ppda: frame-index of aantal hoeken ongeldig"));
            }
            for (c, view) in frame.views.iter().enumerate() {
                let expected = layout.cell(row, c as u32);
                let inside = u64::from(view.x) + u64::from(view.w) <= u64::from(layout.width)
                    && u64::from(view.y) + u64::from(view.h) <= u64::from(layout.height);
                if *view != expected || !inside {
                    return Err(ExportError::Corrupt(format!(
                        ".ppda: celcoördinaten van {} f{k} p{} y{} kloppen niet",
                        clip.token, view.pitch, view.yaw
                    )));
                }
            }
            row += 1;
        }
    }
    if p.maps.len() != ATLAS_MAPS.len() {
        return Err(ident(
            ".ppda: maps moet precies diffuse/normal/depth/specular bevatten",
        ));
    }
    for kind in ATLAS_MAPS {
        let m = p
            .maps
            .get(kind.token())
            .ok_or_else(|| ident(format!(".ppda mist map {}", kind.token())))?;
        if m.file != atlas_png_name(&p.sex, &p.settype, kind) {
            return Err(ExportError::Traversal(format!(
                ".ppda: atlasbestand '{}' is niet de verwachte naam in de exportmap",
                m.file
            )));
        }
        if !is_sha256_hex(&m.sha256) {
            return Err(ExportError::Corrupt(".ppda: atlas sha256 ongeldig".into()));
        }
        if m.width != layout.width || m.height != layout.height {
            return Err(ExportError::Corrupt(format!(
                ".ppda: {} atlasafmetingen {}x{} wijken af van raster {}x{}",
                kind.token(),
                m.width,
                m.height,
                layout.width,
                layout.height
            )));
        }
    }
    Ok(layout)
}

/// A validated `.ppda` whose atlases exist, match their SHA-256 and headers.
#[derive(Debug, Clone)]
pub struct AtlasSet {
    dir: PathBuf,
    pub ppda: Ppda,
    pub layout: AtlasLayout,
}

impl AtlasSet {
    /// Export folder containing the `.ppda` and its atlases.
    pub fn dir(&self) -> &Path {
        &self.dir
    }

    fn read_ppda(path: &Path) -> Result<(PathBuf, Ppda, AtlasLayout), ExportError> {
        let dir = path
            .parent()
            .ok_or_else(|| ExportError::Io(".ppda zonder map".into()))?;
        let dir = dir
            .canonicalize()
            .map_err(|e| ExportError::Io(e.to_string()))?;
        let file_name = path
            .file_name()
            .and_then(|n| n.to_str())
            .ok_or_else(|| ExportError::Io("ongeldige .ppda-naam".into()))?
            .to_string();
        let path = dir.join(&file_name);
        export_set::verify_regular_file(&path, &dir)?;
        let bytes = export_set::read_bounded_file(&path, MAX_PPDA_BYTES)?;
        let text = std::str::from_utf8(&bytes)
            .map_err(|_| ExportError::Corrupt(".ppda is geen UTF-8".into()))?;
        let ppda: Ppda =
            serde_json::from_str(text).map_err(|e| ExportError::Corrupt(format!(".ppda: {e}")))?;
        let layout = validate_ppda(&ppda, &file_name)?;
        Ok((dir, ppda, layout))
    }

    fn read_map(&self, kind: MapKind) -> Result<Vec<u8>, ExportError> {
        let m = &self.ppda.maps[kind.token()];
        let path = self.dir.join(&m.file);
        export_set::verify_regular_file(&path, &self.dir)?;
        let bytes = export_set::read_bounded_file(&path, MAX_ATLAS_PNG_BYTES)?;
        if digest::sha256_hex(&bytes) != m.sha256 {
            return Err(ExportError::Corrupt(format!(
                "checksum mismatch voor '{}'",
                m.file
            )));
        }
        Ok(bytes)
    }

    /// Validate the manifest, then each atlas: regular file inside the folder,
    /// SHA-256, PNG header dimensions and sample format.
    pub fn open(ppda_path: &Path) -> Result<Self, ExportError> {
        let (dir, ppda, layout) = Self::read_ppda(ppda_path)?;
        let set = Self { dir, ppda, layout };
        for kind in ATLAS_MAPS {
            let bytes = set.read_map(kind)?;
            let decoder = png::Decoder::new(std::io::Cursor::new(&bytes[..]));
            let reader = decoder
                .read_info()
                .map_err(|e| ExportError::Corrupt(format!("atlas PNG header: {e}")))?;
            let info = reader.info();
            let (color, depth) = if kind == MapKind::Depth {
                (png::ColorType::GrayscaleAlpha, png::BitDepth::Sixteen)
            } else {
                (png::ColorType::Rgba, png::BitDepth::Eight)
            };
            if info.width != layout.width
                || info.height != layout.height
                || info.color_type != color
                || info.bit_depth != depth
            {
                return Err(ExportError::Corrupt(format!(
                    "{} atlas: afmetingen of kleurtype wijken af van .ppda",
                    kind.token()
                )));
            }
        }
        Ok(set)
    }

    /// Open the single `.ppda` inside a run directory.
    pub fn open_run(run_dir: &Path) -> Result<Self, ExportError> {
        let mut found = Vec::new();
        for entry in fs::read_dir(run_dir).map_err(|e| ExportError::Io(e.to_string()))? {
            let entry = entry.map_err(|e| ExportError::Io(e.to_string()))?;
            let name = entry.file_name();
            if name.to_str().is_some_and(|n| n.ends_with("-atlas.ppda")) {
                found.push(entry.path());
            }
        }
        match found.as_slice() {
            [one] => Self::open(one),
            [] => Err(ExportError::Incomplete(
                "geen .ppda in deze exportmap".into(),
            )),
            _ => Err(ExportError::Identity(
                "meer dan één .ppda in deze exportmap".into(),
            )),
        }
    }

    /// Decode all four atlases (re-verifying SHA-256 on the bytes decoded) with
    /// the full map pixel contract.
    pub fn load(&self) -> Result<LoadedAtlas, ExportError> {
        let decoded = u64::from(self.layout.width) * u64::from(self.layout.height) * 4 * 4;
        if decoded > MAX_DECODED_SET_BYTES {
            return Err(ExportError::Resource(format!(
                "atlasset te groot om te laden ({decoded} bytes gedecodeerd)"
            )));
        }
        let mut maps = BTreeMap::new();
        for kind in ATLAS_MAPS {
            let bytes = self.read_map(kind)?;
            let image = export_set::decode_map_sized(
                &bytes,
                kind,
                self.layout.width,
                self.layout.height,
                MAX_ATLAS_DIM,
            )?;
            maps.insert(kind.token(), image);
        }
        Ok(LoadedAtlas {
            set: self.clone(),
            maps,
        })
    }
}

/// Decoded atlases for one `.ppda`; crops cells for the compositor.
#[derive(Debug, Clone)]
pub struct LoadedAtlas {
    pub set: AtlasSet,
    maps: BTreeMap<&'static str, MapImage>,
}

impl LoadedAtlas {
    pub fn ppda(&self) -> &Ppda {
        &self.set.ppda
    }

    /// Coordinates of one view from the `.ppda`.
    pub fn view(
        &self,
        clip_token: &str,
        frame: u32,
        pitch: i32,
        yaw: u32,
    ) -> Result<PpdaView, ExportError> {
        let clip = self
            .set
            .ppda
            .clips
            .iter()
            .find(|c| c.token == clip_token)
            .ok_or_else(|| ExportError::Incomplete(format!("clip '{clip_token}' niet in .ppda")))?;
        let frame = clip.frames.get(frame as usize).ok_or_else(|| {
            ExportError::Incomplete(format!("frame {frame} niet in clip '{clip_token}'"))
        })?;
        frame
            .views
            .iter()
            .find(|v| v.pitch == pitch && v.yaw == yaw)
            .copied()
            .ok_or_else(|| ExportError::Incomplete(format!("hoek p{pitch} y{yaw} niet in .ppda")))
    }

    /// Crop one map cell exactly as stored.
    pub fn cell(
        &self,
        clip_token: &str,
        frame: u32,
        pitch: i32,
        yaw: u32,
        kind: MapKind,
    ) -> Result<MapImage, ExportError> {
        let v = self.view(clip_token, frame, pitch, yaw)?;
        let atlas_w = self.set.layout.width as usize;
        let (x, y, w, h) = (v.x as usize, v.y as usize, v.w as usize, v.h as usize);
        match &self.maps[kind.token()] {
            MapImage::Rgba8 { rgba, .. } => {
                let mut out = Vec::with_capacity(w * h * 4);
                for row in y..y + h {
                    let start = (row * atlas_w + x) * 4;
                    out.extend_from_slice(&rgba[start..start + w * 4]);
                }
                Ok(MapImage::Rgba8 {
                    width: v.w,
                    height: v.h,
                    rgba: out,
                })
            }
            MapImage::Depth16 { samples, .. } => {
                let mut out = Vec::with_capacity(w * h * 2);
                for row in y..y + h {
                    let start = (row * atlas_w + x) * 2;
                    out.extend_from_slice(&samples[start..start + w * 2]);
                }
                Ok(MapImage::Depth16 {
                    width: v.w,
                    height: v.h,
                    samples: out,
                })
            }
        }
    }
}