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

export const SHADER_GRAPH_SCHEMA = 1 as const;
export type ShaderSocketType = "VALUE" | "VECTOR" | "COLOR" | "BOOLEAN" | "SHADER" | "CLOSURE";
export type ShaderNodeType = "RGB" | "VALUE" | "MIX" | "MATH" | "MAPPING" | "TEX_COORD" | "IMAGE_TEXTURE" | "NORMAL_MAP" | "BUMP" | "PRINCIPLED" | "MATERIAL_OUTPUT";
export type ShaderSocketValue = boolean | number | string | number[];

export interface ShaderSocketIR {
  id: string;
  name: string;
  direction: "INPUT" | "OUTPUT";
  dataType: ShaderSocketType;
  defaultValue?: ShaderSocketValue;
}

export interface ShaderNodeIR {
  id: string;
  type: ShaderNodeType | "UNSUPPORTED";
  name: string;
  sockets: ShaderSocketIR[];
  imageId?: string | null;
  properties?: Record<string, ShaderSocketValue>;
}

export interface ShaderLinkIR {
  fromNodeId: string;
  fromSocketId: string;
  toNodeId: string;
  toSocketId: string;
}

export interface ShaderGraphIR {
  schemaVersion: typeof SHADER_GRAPH_SCHEMA;
  id: string;
  materialId: string;
  nodes: ShaderNodeIR[];
  links: ShaderLinkIR[];
  outputNodeId?: string;
  graphHash?: string;
}

export interface ShaderGraphValidationContext {
  imageIds: ReadonlySet<string>;
  blockedImageIds?: ReadonlySet<string>;
  materialIds?: ReadonlySet<string>;
}

export interface ShaderGraphValidation {
  status: "SUPPORTED" | "BLOCKED";
  issues: Array<{ code: ErrorCode; message: string; path?: string }>;
  cycles: string[][];
}

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

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

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

function socket(value: unknown, path: string): value is ShaderSocketIR {
  if (!record(value) || typeof value.id !== "string" || typeof value.name !== "string" || !["INPUT", "OUTPUT"].includes(value.direction as string) || !["VALUE", "VECTOR", "COLOR", "BOOLEAN", "SHADER", "CLOSURE"].includes(value.dataType as string)) throw new ShaderGraphError("SHADER_INVALID_GRAPH", `${path} is invalid`, path);
  if (value.defaultValue !== undefined && !(typeof value.defaultValue === "boolean" || typeof value.defaultValue === "number" || typeof value.defaultValue === "string" || (Array.isArray(value.defaultValue) && value.defaultValue.every((item) => typeof item === "number" && Number.isFinite(item))))) throw new ShaderGraphError("SHADER_INVALID_GRAPH", `${path}.defaultValue is invalid`, `${path}.defaultValue`);
  return true;
}

const supportedTypes = new Set<ShaderNodeType>(["RGB", "VALUE", "MATH", "IMAGE_TEXTURE", "NORMAL_MAP", "PRINCIPLED", "MATERIAL_OUTPUT"]);
const supportedMathOperations = new Set(["ADD", "SUBTRACT", "MULTIPLY", "DIVIDE", "MINIMUM", "MAXIMUM"]);

export function parseShaderGraph(value: unknown): ShaderGraphIR {
  if (!record(value) || value.schemaVersion !== SHADER_GRAPH_SCHEMA) throw new ShaderGraphError("PROTOCOL_MISMATCH", "Unsupported ShaderGraph schema");
  if (typeof value.id !== "string" || typeof value.materialId !== "string" || value.id.length === 0 || value.materialId.length === 0 || !Array.isArray(value.nodes) || !Array.isArray(value.links)) throw new ShaderGraphError("SHADER_INVALID_GRAPH", "ShaderGraph metadata or arrays are invalid");
  value.nodes.forEach((node, index) => {
    if (!record(node) || typeof node.id !== "string" || typeof node.name !== "string" || typeof node.type !== "string" || !Array.isArray(node.sockets)) throw new ShaderGraphError("SHADER_INVALID_GRAPH", `nodes[${index}] is invalid`, `nodes[${index}]`);
    node.sockets.forEach((item, socketIndex) => socket(item, `nodes[${index}].sockets[${socketIndex}]`));
    if (node.imageId !== undefined && node.imageId !== null && typeof node.imageId !== "string") throw new ShaderGraphError("SHADER_INVALID_GRAPH", `nodes[${index}].imageId is invalid`, `nodes[${index}].imageId`);
    if (node.properties !== undefined && (!record(node.properties) || Object.values(node.properties).some((item) => !(typeof item === "boolean" || typeof item === "number" || typeof item === "string" || (Array.isArray(item) && item.every((entry) => typeof entry === "number" && Number.isFinite(entry))))))) throw new ShaderGraphError("SHADER_INVALID_GRAPH", `nodes[${index}].properties is invalid`, `nodes[${index}].properties`);
  });
  value.links.forEach((link, index) => {
    if (!record(link) || typeof link.fromNodeId !== "string" || typeof link.fromSocketId !== "string" || typeof link.toNodeId !== "string" || typeof link.toSocketId !== "string") throw new ShaderGraphError("SHADER_INVALID_GRAPH", `links[${index}] is invalid`, `links[${index}]`);
  });
  if (value.outputNodeId !== undefined && typeof value.outputNodeId !== "string") throw new ShaderGraphError("SHADER_INVALID_GRAPH", "outputNodeId is invalid", "outputNodeId");
  return value as unknown as ShaderGraphIR;
}

function compatible(from: ShaderSocketIR, to: ShaderSocketIR): boolean {
  if (from.direction !== "OUTPUT" || to.direction !== "INPUT") return false;
  if (from.dataType === to.dataType) return true;
  return (from.dataType === "COLOR" && to.dataType === "VECTOR") || (from.dataType === "VECTOR" && to.dataType === "COLOR") || (from.dataType === "VALUE" && to.dataType === "VECTOR");
}

export function validateShaderGraph(graph: ShaderGraphIR, context: ShaderGraphValidationContext): ShaderGraphValidation {
  const issues: ShaderGraphValidation["issues"] = [];
  const nodes = new Map<string, ShaderNodeIR>();
  const sockets = new Map<string, ShaderSocketIR>();
  for (const [index, node] of graph.nodes.entries()) {
    if (nodes.has(node.id)) issues.push({ code: "SHADER_INVALID_GRAPH", message: `duplicate node ID: ${node.id}`, path: `nodes.${index}` });
    nodes.set(node.id, node);
    if (node.type === "UNSUPPORTED" || !supportedTypes.has(node.type)) issues.push({ code: "SHADER_NODE_UNSUPPORTED", message: `unsupported shader node: ${node.type}`, path: `nodes.${index}.type` });
    const propertyKeys = Object.keys(node.properties ?? {});
    if (node.type === "MATH") {
      const operation = node.properties?.operation;
      if (propertyKeys.length !== 1 || typeof operation !== "string" || !supportedMathOperations.has(operation)) {
        issues.push({ code: "SHADER_NODE_UNSUPPORTED", message: "Math requires one supported operation property", path: `nodes.${index}.properties.operation` });
      }
    }
    else if (propertyKeys.length > 0) issues.push({ code: "SHADER_NODE_UNSUPPORTED", message: `shader node properties are not writable for ${node.type}`, path: `nodes.${index}.properties` });
    if (node.type === "IMAGE_TEXTURE" && (!node.imageId || !context.imageIds.has(node.imageId))) issues.push({ code: "SHADER_EXTERNAL_RESOURCE_MISSING", message: `shader node references a missing image: ${node.imageId ?? "none"}`, path: `nodes.${index}.imageId` });
    else if (node.type === "IMAGE_TEXTURE" && node.imageId && context.blockedImageIds?.has(node.imageId)) issues.push({ code: "SHADER_EXTERNAL_RESOURCE_MISSING", message: `shader image is blocked by the library/path sandbox: ${node.imageId}`, path: `nodes.${index}.imageId` });
    for (const item of node.sockets) {
      if (sockets.has(`${node.id}:${item.id}`)) issues.push({ code: "SHADER_INVALID_GRAPH", message: `duplicate socket ID: ${node.id}:${item.id}`, path: `nodes.${index}.sockets` });
      sockets.set(`${node.id}:${item.id}`, item);
    }
  }
  if (context.materialIds && !context.materialIds.has(graph.materialId)) {
    issues.push({ code: "SHADER_EXTERNAL_RESOURCE_MISSING", message: `shader graph references a missing material: ${graph.materialId}`, path: "materialId" });
  }
  const edges = new Map<string, string[]>();
  const linkedInputs = new Set<string>();
  for (const [index, link] of graph.links.entries()) {
    const from = sockets.get(`${link.fromNodeId}:${link.fromSocketId}`);
    const to = sockets.get(`${link.toNodeId}:${link.toSocketId}`);
    if (!from || !to) {
      issues.push({ code: "SHADER_INVALID_GRAPH", message: "link references an unknown socket", path: `links.${index}` });
      continue;
    }
    if (!compatible(from, to)) issues.push({ code: "SHADER_SOCKET_TYPE_MISMATCH", message: `incompatible shader link ${link.fromNodeId}:${link.fromSocketId} -> ${link.toNodeId}:${link.toSocketId}`, path: `links.${index}` });
    const inputKey = `${link.toNodeId}:${link.toSocketId}`;
    if (linkedInputs.has(inputKey)) issues.push({ code: "SHADER_INVALID_GRAPH", message: `shader input has more than one link: ${inputKey}`, path: `links.${index}` });
    linkedInputs.add(inputKey);
    edges.set(link.fromNodeId, [...(edges.get(link.fromNodeId) ?? []), link.toNodeId]);
  }
  const cycles: string[][] = [];
  const state = new Map<string, 0 | 1 | 2>();
  const path: string[] = [];
  const visit = (id: string): void => {
    const current = state.get(id) ?? 0;
    if (current === 2) return;
    if (current === 1) {
      const start = path.indexOf(id);
      cycles.push(start < 0 ? [id] : [...path.slice(start), id]);
      return;
    }
    state.set(id, 1);
    path.push(id);
    for (const next of edges.get(id) ?? []) visit(next);
    path.pop();
    state.set(id, 2);
  };
  for (const node of graph.nodes) visit(node.id);
  if (cycles.length > 0) issues.push({ code: "SHADER_GRAPH_CYCLE", message: "Shader graph contains a cycle", path: "links" });
  const outputNodes = graph.nodes.filter((node) => node.type === "MATERIAL_OUTPUT");
  if (outputNodes.length !== 1 || (graph.outputNodeId !== undefined && graph.outputNodeId !== outputNodes[0]?.id)) issues.push({ code: "SHADER_INVALID_GRAPH", message: "Shader graph must have exactly one Material Output", path: "outputNodeId" });
  return { status: issues.length > 0 ? "BLOCKED" : "SUPPORTED", issues, cycles };
}

export function gateShaderGraph(value: unknown, context: ShaderGraphValidationContext = { imageIds: new Set<string>() }): CapabilityGateResult {
  try {
    const graph = parseShaderGraph(value);
    const result = validateShaderGraph(graph, context);
    if (result.status === "SUPPORTED") return readyGate("N-013", "SHADER_NODE_GRAPH");
    return blockedGate("N-013", "SHADER_NODE_GRAPH", result.issues.map((issue) => capabilityIssue(issue.code, issue.message, issue.path)));
  }
  catch (error) {
    const issue = error as ShaderGraphError;
    return blockedGate("N-013", "SHADER_NODE_GRAPH", [capabilityIssue(issue.code ?? "SHADER_INVALID_GRAPH", issue.message, issue.path)]);
  }
}