export const CURVE_GIZMO_SCHEMA = 1 as const;

export const CURVE_GIZMO_BUDGET = {
  maxHandles: 256,
  maxIdLength: 256,
  maxCoordinate: 1_000_000,
} as const;

export type CurveGizmoHandleSide = "LEFT" | "RIGHT" | "CONTROL";
export type CurveGizmoPhase = "PREVIEW" | "COMMIT";

export interface CurveGizmoHandleIR {
  pointIndex: number;
  side: CurveGizmoHandleSide;
  position: [number, number, number];
}

export interface CurveGizmoDragIR {
  schemaVersion: typeof CURVE_GIZMO_SCHEMA;
  dataId: string;
  baseRevision: number;
  phase: CurveGizmoPhase;
  axis: 0 | 1 | 2;
  axisVector?: [number, number, number];
  delta: [number, number, number];
  handles: CurveGizmoHandleIR[];
}

export interface CurveGizmoFrameIR {
  origin: [number, number, number];
  axes: [[number, number, number], [number, number, number], [number, number, number]];
}

export interface CurveGizmoScreenFrameIR {
  origin: [number, number];
  axes: [[number, number], [number, number], [number, number]];
}

export interface AppliedCurveGizmoDragIR {
  dataId: string;
  phase: CurveGizmoPhase;
  axis: 0 | 1 | 2;
  axisVector?: [number, number, number];
  revision: number;
  handles: CurveGizmoHandleIR[];
}

function fail(path: string, message: string): never {
  throw new Error(`CURVE_GIZMO_INVALID: ${path} ${message}`);
}

function record(value: unknown, path: string): Record<string, unknown> {
  if (typeof value !== "object" || value === null || Array.isArray(value)) fail(path, "must be an object");
  return value as Record<string, unknown>;
}

function integer(value: unknown, path: string, minimum = 0): number {
  if (typeof value !== "number" || !Number.isSafeInteger(value) || value < minimum) fail(path, "must be a bounded integer");
  return value;
}

function finite(value: unknown, path: string): number {
  if (typeof value !== "number" || !Number.isFinite(value) || Math.abs(value) > CURVE_GIZMO_BUDGET.maxCoordinate) fail(path, "is outside the finite coordinate budget");
  return value;
}

function vector(value: unknown, path: string): [number, number, number] {
  if (!Array.isArray(value) || value.length !== 3) fail(path, "must contain three coordinates");
  return [finite(value[0], `${path}[0]`), finite(value[1], `${path}[1]`), finite(value[2], `${path}[2]` )];
}

function length(value: readonly number[]): number {
  return Math.hypot(value[0], value[1], value[2]);
}

function normalize(value: readonly number[], path: string): [number, number, number] {
  const magnitude = length(value);
  if (!Number.isFinite(magnitude) || magnitude < 1e-8) fail(path, "must have a finite non-zero direction");
  return [value[0] / magnitude, value[1] / magnitude, value[2] / magnitude];
}

function dot(left: readonly number[], right: readonly number[]): number {
  return left[0] * right[0] + left[1] * right[1] + left[2] * right[2];
}

function cross(left: readonly number[], right: readonly number[]): [number, number, number] {
  return [left[1] * right[2] - left[2] * right[1], left[2] * right[0] - left[0] * right[2], left[0] * right[1] - left[1] * right[0]];
}

export function deriveCurveHandleGizmoFrame(controlPoints: ArrayLike<number>, handles: readonly CurveGizmoHandleIR[]): CurveGizmoFrameIR {
  if (controlPoints.length === 0 || controlPoints.length % 3 !== 0) fail("controlPoints", "must contain finite XYZ coordinates");
  for (let index = 0; index < controlPoints.length; index += 1) {
    if (!Number.isFinite(controlPoints[index])) fail("controlPoints", "must contain finite XYZ coordinates");
  }
  if (handles.length === 0 || handles.length > CURVE_GIZMO_BUDGET.maxHandles) fail("handles", "exceeds the handle budget");
  const ordered = [...handles].sort((left, right) => left.pointIndex - right.pointIndex || left.side.localeCompare(right.side));
  const origin: [number, number, number] = [0, 0, 0];
  const directions: Array<[number, number, number]> = [];
  for (const [index, handle] of ordered.entries()) {
    if (!Number.isSafeInteger(handle.pointIndex) || handle.pointIndex < 0 || handle.pointIndex * 3 + 2 >= controlPoints.length || handle.side === "CONTROL") fail(`handles[${index}]`, "must identify a Curve handle with an existing control point");
    vector(handle.position, `handles[${index}].position`);
    origin[0] += handle.position[0];
    origin[1] += handle.position[1];
    origin[2] += handle.position[2];
    const point = handle.pointIndex * 3;
    directions.push(normalize([
      handle.position[0] - controlPoints[point],
      handle.position[1] - controlPoints[point + 1],
      handle.position[2] - controlPoints[point + 2],
    ], `handles[${index}].direction`));
  }
  origin[0] /= ordered.length;
  origin[1] /= ordered.length;
  origin[2] /= ordered.length;
  const reference = directions[0];
  const aligned = directions.map((direction) => dot(direction, reference) < 0 ? direction.map((value) => -value) as [number, number, number] : direction);
  const axisX = normalize(aligned.reduce<[number, number, number]>((sum, direction) => [sum[0] + direction[0], sum[1] + direction[1], sum[2] + direction[2]], [0, 0, 0]), "handles.directionAverage");
  const up: [number, number, number] = Math.abs(axisX[2]) < 0.9 ? [0, 0, 1] : [0, 1, 0];
  const axisY = normalize(cross(up, axisX), "gizmo.axisY");
  const axisZ = normalize(cross(axisX, axisY), "gizmo.axisZ");
  return { origin, axes: [axisX, axisY, axisZ] };
}

export function curveGizmoAxisDelta(frame: CurveGizmoFrameIR, axis: 0 | 1 | 2, amount: number): [number, number, number] {
  if (!Number.isFinite(amount) || Math.abs(amount) > CURVE_GIZMO_BUDGET.maxCoordinate) fail("amount", "is outside the finite coordinate budget");
  const direction = normalize(frame.axes[axis], `frame.axes[${axis}]`);
  return [direction[0] * amount, direction[1] * amount, direction[2] * amount];
}

export function parseCurveGizmoDrag(value: unknown, expectedRevision?: number): CurveGizmoDragIR {
  const drag = record(value, "drag");
  if (drag.schemaVersion !== CURVE_GIZMO_SCHEMA) fail("schemaVersion", "is unsupported");
  if (typeof drag.dataId !== "string" || drag.dataId.length === 0 || drag.dataId.length > CURVE_GIZMO_BUDGET.maxIdLength) fail("dataId", "is invalid");
  const baseRevision = integer(drag.baseRevision, "baseRevision");
  if (expectedRevision !== undefined && baseRevision !== expectedRevision) throw new Error("REVISION_CONFLICT: Curve gizmo request is stale");
  if (drag.phase !== "PREVIEW" && drag.phase !== "COMMIT") fail("phase", "is invalid");
  if (drag.axis !== 0 && drag.axis !== 1 && drag.axis !== 2) fail("axis", "must be X, Y or Z");
  const delta = vector(drag.delta, "delta");
  const axisVector = drag.axisVector === undefined ? undefined : normalize(vector(drag.axisVector, "axisVector"), "axisVector");
  if (axisVector) {
    const deltaLength = length(delta);
    if (deltaLength > 0 && length(cross(delta, axisVector)) > Math.max(1e-7, deltaLength * 1e-6)) fail("delta", "must be parallel to the selected local axis");
  }
  else if (delta.some((component, axis) => axis !== drag.axis && component !== 0)) fail("delta", "must only move along the selected axis");
  if (!Array.isArray(drag.handles) || drag.handles.length === 0 || drag.handles.length > CURVE_GIZMO_BUDGET.maxHandles) fail("handles", "exceeds the handle budget");
  const seen = new Set<string>();
  const handles = drag.handles.map((item, index) => {
    const handle = record(item, `handles[${index}]`);
    const pointIndex = integer(handle.pointIndex, `handles[${index}].pointIndex`);
    if (handle.side !== "LEFT" && handle.side !== "RIGHT" && handle.side !== "CONTROL") fail(`handles[${index}].side`, "is invalid");
    const side = handle.side as CurveGizmoHandleSide;
    const key = `${pointIndex}:${side}`;
    if (seen.has(key)) fail(`handles[${index}]`, "duplicates a selected handle");
    seen.add(key);
    return { pointIndex, side, position: vector(handle.position, `handles[${index}].position`) };
  });
  return { schemaVersion: CURVE_GIZMO_SCHEMA, dataId: drag.dataId, baseRevision, phase: drag.phase, axis: drag.axis, axisVector, delta, handles };
}

export function applyCurveGizmoDelta(value: unknown, expectedRevision?: number): AppliedCurveGizmoDragIR {
  const drag = parseCurveGizmoDrag(value, expectedRevision);
  const handles = drag.handles.map((handle) => ({
    ...handle,
    position: [handle.position[0] + drag.delta[0], handle.position[1] + drag.delta[1], handle.position[2] + drag.delta[2]] as [number, number, number],
  }));
  handles.forEach((handle, index) => vector(handle.position, `handles[${index}].position`));
  return { dataId: drag.dataId, phase: drag.phase, axis: drag.axis, axisVector: drag.axisVector, revision: drag.baseRevision + (drag.phase === "COMMIT" ? 1 : 0), handles };
}