//! The edit graph — an ordered set of operations (ARCH §3.4).
//!
//! CPU-side state, deliberately. The GPU device can be lost and rebuilt at any
//! moment on Android (ARCH §6.10), and recovery is only tractable because
//! everything needed to re-render lives here rather than in GPU memory.
//!
//! Order is data, not code: operations run in the sequence this holds them,
//! so reordering the pipeline needs no code change.

use crate::descriptor::{LocalizedKey, OpDescriptor, OpId, ParamId, ParamKind, Presentation};
use crate::framing::{CropRect, Framing};
use crate::operation::{compose_with_framing, ComposedShader, Operation};
use crate::ops;

/// TRACES: FR-DEV-3a
/// What one operation offers, as plain data.
///
/// Deliberately owned rather than borrowed, and free of any trait objects:
/// the UI receives a snapshot it can hold across a frame without borrowing
/// the graph, and nothing in it hints at how the operation is implemented.
#[derive(Debug, Clone, PartialEq)]
pub struct OpCapability {
    pub id: OpId,
    /// A key for the UI's own catalogue. Never a display string — resolving
    /// it needs a localiser, which `core/` must not depend on.
    pub label: LocalizedKey,
    /// Whether this operation currently alters the image. A UI may use it to
    /// mark a section as modified, or to offer a per-operation reset.
    pub active: bool,
    pub params: Vec<ParamCapability>,
    /// A hint that several of `params` form one conceptual control.
    ///
    /// `None` means one control per parameter. A UI that does not implement
    /// the named widget may ignore this and render sliders — the parameters
    /// are ordinary scalars either way, so nothing becomes unreachable.
    pub presentation: Option<Presentation>,
}

/// TRACES: FR-DEV-3a | FR-DEV-3b
/// What one parameter offers.
///
/// [`Self::kind`] is what selects the control: the UI maps each `ParamKind`
/// to a widget appropriate to the current input modality (ARCH §4.3), and
/// never switches on the parameter's identity.
#[derive(Debug, Clone, PartialEq)]
pub struct ParamCapability {
    pub id: ParamId,
    pub label: LocalizedKey,
    pub kind: ParamKind,
    pub default: f32,
    /// The current setting, so the control opens where the edit actually is.
    pub value: f32,
}

impl ParamCapability {
    /// Whether this parameter is away from its default.
    pub fn is_modified(&self) -> bool {
        self.value != self.default
    }
}

/// An ordered pipeline of operations, plus how the result is framed.
pub struct EditGraph {
    ops: Vec<Box<dyn Operation>>,
    /// Crop, straighten, rotation and flips.
    ///
    /// Held apart from `ops` rather than in the list because it is not one:
    /// an operation transforms a colour, and framing decides which source
    /// pixel that colour is read from — and changes the output's dimensions,
    /// which no colour operation can do. See [`crate::framing`].
    framing: Framing,
}

impl EditGraph {
    /// The default develop chain, in pipeline order (ARCH §5.2).
    ///
    /// Order is not arbitrary. White balance and exposure come first because
    /// they are corrections to how the scene was captured, and the tonal
    /// operations that follow should act on a correctly exposed image.
    /// Colour comes last, so vibrance responds to the tones the user has
    /// actually settled on rather than the ones they started with.
    pub fn default_chain() -> Self {
        Self {
            ops: vec![
                Box::new(ops::WhiteBalance::new()),
                Box::new(ops::Exposure::new()),
                Box::new(ops::Contrast::new()),
                Box::new(ops::HighlightsShadows::new()),
                Box::new(ops::BlacksWhites::new()),
                // After the region controls, so the curve is the final word
                // on tone: a photographer reaches for it to fix what the
                // fixed-weight controls could not place exactly.
                Box::new(ops::ToneCurve::new()),
                Box::new(ops::Brilliance::new()),
                Box::new(ops::Vibrance::new()),
                Box::new(ops::Saturation::new()),
                // The mixer comes last: it is the finishing control, and it
                // should act on the tones the user has already settled.
                Box::new(ops::ColourMixer::new()),
            ],
            framing: Framing::new(),
        }
    }

    /// The framing — crop, straighten, rotation and flips.
    ///
    /// Reached directly rather than through `set_param` because the crop is a
    /// rectangle, and driving one through four independent scalars makes an
    /// interactive drag four clamps that can disagree. The parameter route
    /// still exists for the sidecar, which has only scalars to work with.
    pub fn framing(&self) -> &Framing {
        &self.framing
    }

    pub fn framing_mut(&mut self) -> &mut Framing {
        &mut self.framing
    }

    /// The size this graph renders to, given a source of `(w, h)`.
    ///
    /// Cropping and quarter turns change it, so the caller allocating the
    /// output texture must ask rather than assume the source size.
    pub fn output_size(&self, width: u32, height: u32) -> (u32, u32) {
        self.framing.output_size(width, height)
    }

    /// Descriptors for every operation, in order.
    ///
    /// Operations only — framing is not one, and is reached through
    /// [`Self::framing`] or the capability list. The distinction matters here
    /// because this is what the codegen tests count `---- ` shader blocks
    /// against, and framing generates a prologue rather than a colour block.
    /// A UI wanting everything should read [`Self::capabilities`] (FR-DEV-3a).
    pub fn descriptors(&self) -> Vec<&'static OpDescriptor> {
        self.ops.iter().map(|o| o.descriptor()).collect()
    }

    /// TRACES: FR-DEV-3a | FR-DEV-3c
    /// Everything a UI needs to build its controls.
    ///
    /// **This is the only thing the UI should read.** It must not know that
    /// exposure exists, that saturation is implemented with a mix, or that
    /// any of this becomes a shader — it walks this list and instantiates a
    /// control per entry according to the [`ParamKind`]. A new operation
    /// therefore appears in the interface with no UI change at all
    /// (FR-DEV-3c), and an operation removed from the chain disappears from
    /// it just as automatically.
    ///
    /// Current values are included so the UI has no separate initialisation
    /// step, and so reopening an edited image shows where the sliders
    /// actually are.
    pub fn capabilities(&self) -> Vec<OpCapability> {
        let ops = self.ops.iter().map(|op| {
            let desc = op.descriptor();
            OpCapability {
                id: desc.id,
                label: desc.label,
                active: op.is_active(),
                params: desc
                    .params
                    .iter()
                    .map(|p| ParamCapability {
                        id: p.id,
                        label: p.label,
                        kind: p.kind.clone(),
                        default: p.default,
                        value: op.param(p.id),
                    })
                    .collect(),
                presentation: op.presentation(),
            }
        });

        // Framing last, matching where it sits in the pipeline: the crop is
        // decided after the image looks right, not before.
        let desc = self.framing.descriptor();
        let framing = OpCapability {
            id: desc.id,
            label: desc.label,
            active: self.framing.is_active(),
            params: desc
                .params
                .iter()
                .map(|p| ParamCapability {
                    id: p.id,
                    label: p.label,
                    kind: p.kind.clone(),
                    default: p.default,
                    value: self.framing.param(p.id),
                })
                .collect(),
            // Framing is not an `Operation`, so it has no `presentation` to
            // ask for. A crop overlay is a viewport interaction rather than a
            // panel widget, which is a different mechanism again.
            presentation: None,
        };

        ops.chain(std::iter::once(framing)).collect()
    }

    /// Set a parameter, clamping to the descriptor's declared range.
    ///
    /// Clamping here rather than in each operation means an operation never
    /// has to defend against an out-of-range value, and a corrupt sidecar
    /// cannot reach a shader.
    pub fn set_param(&mut self, op: OpId, param: ParamId, value: f32) {
        if op == crate::framing::ID {
            let Some(desc) = self.framing.descriptor().param(param) else {
                log::warn!("unknown parameter {param} on {op}; ignoring");
                return;
            };
            self.framing.set_param(param, desc.clamp(value));
            return;
        }

        let Some(operation) = self.ops.iter_mut().find(|o| o.descriptor().id == op) else {
            // A sidecar naming an operation this build does not have. The
            // rest of the edit must still apply.
            log::warn!("unknown operation {op}; ignoring");
            return;
        };
        let clamped = match operation.descriptor().param(param) {
            Some(d) => d.clamp(value),
            None => {
                log::warn!("unknown parameter {param} on {op}; ignoring");
                return;
            }
        };
        operation.set_param(param, clamped);
    }

    /// Read a parameter back.
    pub fn param(&self, op: OpId, param: ParamId) -> Option<f32> {
        if op == crate::framing::ID {
            return self
                .framing
                .descriptor()
                .param(param)
                .map(|_| self.framing.param(param));
        }
        self.ops
            .iter()
            .find(|o| o.descriptor().id == op)
            .map(|o| o.param(param))
    }

    /// Reset every parameter of every operation, and the framing, to default.
    pub fn reset(&mut self) {
        for op in &mut self.ops {
            for p in op.descriptor().params {
                op.set_param(p.id, p.default);
            }
        }
        self.framing.reset();
    }

    /// Set the crop rectangle. Clamped to keep it inside the frame.
    pub fn set_crop(&mut self, rect: CropRect) {
        self.framing.set_crop(rect);
    }

    pub fn crop(&self) -> CropRect {
        self.framing.crop()
    }

    /// Rotate by quarter turns, wrapping. The rotate-left/right buttons.
    pub fn rotate_quarters(&mut self, turns: i32) {
        self.framing.rotate_quarters(turns);
    }

    /// Whether any operation, or the framing, currently changes the image.
    pub fn is_neutral(&self) -> bool {
        !self.ops.iter().any(|o| o.is_active()) && !self.framing.is_active()
    }

    /// Generate the fused shader for the current state.
    pub fn compose(&self) -> ComposedShader {
        compose_with_framing(&self.ops, &self.framing)
    }
}

impl Default for EditGraph {
    fn default() -> Self {
        Self::default_chain()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::ops::{exposure, white_balance};

    #[test]
    fn a_fresh_graph_is_neutral() {
        // Opening an unedited image must produce the image, not an
        // interpretation of it.
        let g = EditGraph::default_chain();
        assert!(g.is_neutral());
        assert_eq!(
            g.compose().source.matches("---- ").count(),
            0,
            "a neutral graph must generate no operation blocks"
        );
    }

    #[test]
    fn the_default_chain_exposes_every_operation() {
        let g = EditGraph::default_chain();
        let ids: Vec<&str> = g.descriptors().iter().map(|d| d.id.0).collect();
        for expected in [
            "white_balance",
            "exposure",
            "highlights_shadows",
            "blacks_whites",
            "brilliance",
            "vibrance",
            "saturation",
        ] {
            assert!(ids.contains(&expected), "{expected} missing from the chain");
        }
    }

    #[test]
    fn white_balance_and_exposure_precede_the_tonal_operations() {
        // Corrections to capture must come before interpretation of tone, or
        // the tonal controls act on a wrongly exposed image.
        let g = EditGraph::default_chain();
        let ids: Vec<&str> = g.descriptors().iter().map(|d| d.id.0).collect();
        let pos = |id: &str| ids.iter().position(|x| *x == id).expect(id);
        assert!(pos("white_balance") < pos("highlights_shadows"));
        assert!(pos("exposure") < pos("highlights_shadows"));
        assert!(pos("highlights_shadows") < pos("vibrance"));
    }

    #[test]
    fn setting_a_parameter_activates_its_operation() {
        let mut g = EditGraph::default_chain();
        g.set_param(exposure::ID, exposure::EXPOSURE, 1.5);
        assert!(!g.is_neutral());
        assert_eq!(g.param(exposure::ID, exposure::EXPOSURE), Some(1.5));
        assert!(g.compose().source.contains("---- exposure ----"));
    }

    #[test]
    fn values_are_clamped_to_the_descriptor() {
        // The guarantee that lets each operation skip range checks.
        let mut g = EditGraph::default_chain();
        g.set_param(exposure::ID, exposure::EXPOSURE, 99.0);
        assert_eq!(g.param(exposure::ID, exposure::EXPOSURE), Some(5.0));
    }

    #[test]
    fn an_unknown_operation_is_ignored_rather_than_panicking() {
        // A sidecar from a newer version names operations this build lacks.
        // The rest of the edit must still load.
        let mut g = EditGraph::default_chain();
        g.set_param(OpId("time_machine"), ParamId("year"), 1994.0);
        assert!(g.is_neutral());
    }

    #[test]
    fn an_unknown_parameter_is_ignored() {
        let mut g = EditGraph::default_chain();
        g.set_param(exposure::ID, ParamId("nonexistent"), 3.0);
        assert!(g.is_neutral());
    }

    #[test]
    fn reset_returns_every_operation_to_neutral() {
        let mut g = EditGraph::default_chain();
        g.set_param(exposure::ID, exposure::EXPOSURE, 2.0);
        g.set_param(white_balance::ID, white_balance::TEMPERATURE, 50.0);
        assert!(!g.is_neutral());

        g.reset();
        assert!(g.is_neutral(), "reset must clear every operation");
    }

    #[test]
    fn only_active_operations_reach_the_shader() {
        // The composition property, end to end: two adjustments out of seven
        // available must generate a shader doing exactly two things.
        let mut g = EditGraph::default_chain();
        g.set_param(exposure::ID, exposure::EXPOSURE, 1.0);
        g.set_param(white_balance::ID, white_balance::TINT, 25.0);

        let shader = g.compose();
        assert_eq!(shader.source.matches("---- ").count(), 2);
        assert!(shader.source.contains("---- exposure ----"));
        assert!(shader.source.contains("---- white_balance ----"));
        assert!(!shader.source.contains("---- saturation ----"));
    }

    #[test]
    fn moving_a_slider_does_not_change_the_shader_structure() {
        // What makes the pipeline cache worth having: dragging a slider must
        // reuse the compiled pipeline and upload uniforms only.
        let mut g = EditGraph::default_chain();
        g.set_param(exposure::ID, exposure::EXPOSURE, 1.0);
        let first = g.compose();

        g.set_param(exposure::ID, exposure::EXPOSURE, 2.0);
        let second = g.compose();

        assert_eq!(first.structure_hash, second.structure_hash);
        assert_eq!(first.source, second.source);
        assert_ne!(first.uniforms, second.uniforms);
    }

    #[test]
    fn capabilities_describe_every_operation_and_parameter() {
        // The UI builds its whole panel from this. Anything missing here is
        // something the UI would have to hardcode.
        let g = EditGraph::default_chain();
        let caps = g.capabilities();
        // Every operation, plus framing — which is not an operation and so
        // is absent from `descriptors`, but must still reach the panel.
        assert_eq!(caps.len(), g.descriptors().len() + 1);
        assert!(
            caps.iter().any(|c| c.id == crate::framing::ID),
            "framing must appear in the capability list, or the UI cannot \
             build a crop control without naming it"
        );

        for cap in &caps {
            assert!(!cap.params.is_empty(), "{} exposes no parameters", cap.id);
            for p in &cap.params {
                // A control cannot be built without a range.
                match &p.kind {
                    ParamKind::Scalar { min, max, .. } => {
                        assert!(min < max, "{}.{} has an empty range", cap.id, p.id);
                        assert!(
                            (*min..=*max).contains(&p.default),
                            "{}.{} default is outside its range",
                            cap.id,
                            p.id
                        );
                    }
                    ParamKind::Bool => {}
                }
            }
        }
    }

    #[test]
    fn capabilities_report_current_values_not_just_defaults() {
        // So reopening an edited image shows the sliders where the edit left
        // them, with no separate initialisation path in the UI.
        let mut g = EditGraph::default_chain();
        g.set_param(exposure::ID, exposure::EXPOSURE, 1.25);

        let cap = g
            .capabilities()
            .into_iter()
            .find(|c| c.id == exposure::ID)
            .expect("exposure is in the chain");
        let p = &cap.params[0];
        assert_eq!(p.value, 1.25);
        assert_eq!(p.default, 0.0);
        assert!(p.is_modified());
        assert!(cap.active);
    }

    #[test]
    fn a_fresh_graph_reports_nothing_modified() {
        for cap in EditGraph::default_chain().capabilities() {
            assert!(!cap.active, "{} should start inactive", cap.id);
            for p in &cap.params {
                assert!(
                    !p.is_modified(),
                    "{}.{} should start at default",
                    cap.id,
                    p.id
                );
            }
        }
    }

    #[test]
    fn capabilities_survive_a_round_trip_through_set_param() {
        // The UI reads a capability, writes the value back, and must get the
        // same thing out — no hidden scaling between the two.
        //
        // Written at the parameter's declared precision, because that is what
        // the UI can actually produce: a control declaring 0 decimals emits
        // whole numbers, and a stage free to quantise to them is behaving
        // correctly rather than losing the value.
        let mut g = EditGraph::default_chain();
        for cap in g.capabilities() {
            for p in &cap.params {
                if let ParamKind::Scalar { max, precision, .. } = p.kind {
                    let step = 10f32.powi(i32::from(precision));
                    let target = (max * 0.5 * step).round() / step;
                    g.set_param(cap.id, p.id, target);
                    assert_eq!(
                        g.param(cap.id, p.id),
                        Some(target),
                        "{}.{} did not round-trip",
                        cap.id,
                        p.id
                    );
                }
            }
        }
    }

    #[test]
    fn adding_an_operation_needs_no_ui_change() {
        // FR-DEV-3c, asserted structurally: everything a control needs is
        // reachable from the capability list, so a new operation appears
        // without the UI naming it. If this test needs editing to add an
        // operation, the abstraction has leaked.
        let g = EditGraph::default_chain();
        let rendered: Vec<String> = g
            .capabilities()
            .iter()
            .flat_map(|c| {
                c.params.iter().map(move |p| match p.kind {
                    ParamKind::Scalar {
                        min,
                        max,
                        precision,
                        ..
                    } => format!(
                        "{}/{}: slider {min}..{max} @{precision} = {}",
                        c.label.0, p.label.0, p.value
                    ),
                    ParamKind::Bool => format!("{}/{}: switch", c.label.0, p.label.0),
                })
            })
            .collect();

        // Counted from the chain, not a literal: this test must not need
        // editing when an operation is added, or it would be asserting the
        // opposite of what it claims.
        let expected: usize = g.capabilities().iter().map(|c| c.params.len()).sum();
        assert_eq!(rendered.len(), expected);
        assert!(rendered.iter().all(|r| !r.is_empty()));
        assert!(
            expected > 40,
            "the chain should now carry the mixer's 36 parameters too"
        );
    }

    #[test]
    fn enabling_another_operation_does_change_the_structure() {
        let mut g = EditGraph::default_chain();
        g.set_param(exposure::ID, exposure::EXPOSURE, 1.0);
        let before = g.compose().structure_hash;

        g.set_param(
            crate::ops::colour::SATURATION_ID,
            crate::ops::colour::SATURATION,
            30.0,
        );
        assert_ne!(before, g.compose().structure_hash);
    }
}