import { blockedGate, capabilityIssue, readyGate, type CapabilityGateResult } from "./capability-gates";
import type { ErrorCode } from "./error";

export const PAINT_PBVH_CAPABILITY_SCHEMA = 1 as const;
export const PAINT_PBVH_WASM_ENTRYPOINT = "_web_engine_apply_pbvh_stroke" as const;

export type PaintPBVHDomain = "SCULPT" | "VERTEX_COLOR" | "WEIGHT" | "TEXTURE";

const BRUSH_INVENTORY = {
  SCULPT: [
    "DRAW", "SMOOTH", "PINCH", "INFLATE", "GRAB", "LAYER", "CLAY", "NUDGE", "THUMB",
    "SNAKE_HOOK", "ROTATE", "SIMPLIFY", "CREASE", "BLOB", "CLAY_STRIPS", "MASK",
    "DRAW_SHARP", "ELASTIC_DEFORM", "POSE", "MULTIPLANE_SCRAPE", "SLIDE_RELAX",
    "CLAY_THUMB", "CLOTH", "DRAW_FACE_SETS", "PAINT", "SMEAR", "BOUNDARY",
    "DISPLACEMENT_ERASER", "DISPLACEMENT_SMEAR", "PLANE", "BLUR", "SCENE_PROJECT",
  ],
  VERTEX_COLOR: ["DRAW", "BLUR", "AVERAGE", "SMEAR"],
  WEIGHT: ["DRAW", "BLUR", "AVERAGE", "SMEAR"],
  TEXTURE: ["DRAW", "SOFTEN", "SMEAR", "CLONE", "FILL", "MASK"],
} as const satisfies Record<PaintPBVHDomain, readonly string[]>;

export interface PaintPBVHBrushInventoryEntry {
  domain: PaintPBVHDomain;
  brush: string;
  source: "blender-5.2.0/source/blender/makesdna/DNA_brush_enums.h";
}

export interface PaintPBVHCapabilityRequest {
  schemaVersion: typeof PAINT_PBVH_CAPABILITY_SCHEMA;
  operation: "PBVH_BRUSH";
  domain: PaintPBVHDomain;
  brush: string;
  objectId: string;
  meshId: string;
  baseRevision: number;
}

export interface PaintPBVHCapabilityContext {
  nativeEntrypointPresent: boolean;
  sessionContextReady: boolean;
  verifiedBrushes: ReadonlySet<string>;
  currentRevision?: number;
  currentObjectId?: string;
  currentMeshId?: string;
}

export class PaintPBVHCapabilityError extends Error {
  readonly code: ErrorCode;
  readonly path?: string;

  constructor(code: ErrorCode, message: string, path?: string) {
    super(message);
    this.name = "PaintPBVHCapabilityError";
    this.code = code;
    this.path = path;
  }
}

function fail(code: ErrorCode, message: string, path?: string): never {
  throw new PaintPBVHCapabilityError(code, message, path);
}

function record(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null && !Array.isArray(value);
}

function stableId(value: unknown, prefix: "object:" | "mesh:", path: string): string {
  if (typeof value !== "string" || !value.startsWith(prefix) || value.length <= prefix.length || value.length > 512) {
    fail("PAINT_SCHEMA_INVALID", `${path} must be a bounded ${prefix.slice(0, -1)} stable ID`, path);
  }
  return value;
}

export function paintPBVHBrushInventory(): PaintPBVHBrushInventoryEntry[] {
  return (Object.entries(BRUSH_INVENTORY) as Array<[PaintPBVHDomain, readonly string[]]>).flatMap(([domain, brushes]) =>
    brushes.map((brush) => ({
      domain,
      brush,
      source: "blender-5.2.0/source/blender/makesdna/DNA_brush_enums.h" as const,
    })),
  );
}

export function parsePaintPBVHCapabilityRequest(value: unknown): PaintPBVHCapabilityRequest {
  if (!record(value)) fail("PAINT_SCHEMA_INVALID", "PBVH capability request must be an object");
  const allowed = ["schemaVersion", "operation", "domain", "brush", "objectId", "meshId", "baseRevision"];
  const extra = Object.keys(value).find((key) => !allowed.includes(key));
  if (extra) fail("PAINT_SCHEMA_INVALID", `PBVH capability request contains unsupported field ${extra}`, extra);
  if (value.schemaVersion !== PAINT_PBVH_CAPABILITY_SCHEMA) fail("PROTOCOL_MISMATCH", "Unsupported PBVH capability schema", "schemaVersion");
  if (value.operation !== "PBVH_BRUSH") fail("PAINT_SCHEMA_INVALID", "operation must be PBVH_BRUSH", "operation");
  if (typeof value.domain !== "string" || !(value.domain in BRUSH_INVENTORY)) {
    fail("PAINT_SCHEMA_INVALID", "domain is not a PBVH paint domain", "domain");
  }
  const domain = value.domain as PaintPBVHDomain;
  if (typeof value.brush !== "string" || !(BRUSH_INVENTORY[domain] as readonly string[]).includes(value.brush)) {
    fail("PAINT_PBVH_BRUSH_UNVERIFIED", `Brush ${String(value.brush)} is not in the Blender 5.2 ${domain} inventory`, "brush");
  }
  if (!Number.isSafeInteger(value.baseRevision) || (value.baseRevision as number) < 0) {
    fail("PAINT_SCHEMA_INVALID", "baseRevision must be a non-negative safe integer", "baseRevision");
  }
  return {
    schemaVersion: PAINT_PBVH_CAPABILITY_SCHEMA,
    operation: "PBVH_BRUSH",
    domain,
    brush: value.brush,
    objectId: stableId(value.objectId, "object:", "objectId"),
    meshId: stableId(value.meshId, "mesh:", "meshId"),
    baseRevision: value.baseRevision as number,
  };
}

export function gatePaintPBVHCapability(
  value: unknown,
  context: PaintPBVHCapabilityContext,
): CapabilityGateResult {
  const request = parsePaintPBVHCapabilityRequest(value);
  const capability = `PBVH_${request.domain}_${request.brush}`;
  if (context.currentRevision !== undefined && request.baseRevision !== context.currentRevision) {
    return blockedGate("N-017", capability, [
      capabilityIssue("REVISION_CONFLICT", "PBVH capability request is stale", "baseRevision"),
    ]);
  }
  if ((context.currentObjectId !== undefined && request.objectId !== context.currentObjectId) ||
      (context.currentMeshId !== undefined && request.meshId !== context.currentMeshId)) {
    return blockedGate("N-017", capability, [
      capabilityIssue("PAINT_SCHEMA_INVALID", "PBVH request does not target the current Mesh object", "objectId"),
    ]);
  }
  if (!context.nativeEntrypointPresent) {
    return blockedGate("N-017", capability, [
      capabilityIssue(
        "PAINT_PBVH_UNAVAILABLE",
        `${PAINT_PBVH_WASM_ENTRYPOINT} is not present in the WebEngine WASM build`,
        "operation",
        false,
      ),
    ]);
  }
  if (!context.sessionContextReady) {
    return blockedGate("N-017", capability, [
      capabilityIssue("PAINT_PBVH_CONTEXT_UNAVAILABLE", "The Blender PBVH paint session context is not initialized", "operation"),
    ]);
  }
  if (!context.verifiedBrushes.has(`${request.domain}:${request.brush}`)) {
    return blockedGate("N-017", capability, [
      capabilityIssue("PAINT_PBVH_BRUSH_UNVERIFIED", "This PBVH brush has no desktop/WASM golden", "brush"),
    ]);
  }
  return readyGate("N-017", capability);
}