import { isValidCircuitProtectionRecord } from "../../shared/validation/protection-device.schemas.js";
import type {
  BreakerTripCharacteristic,
  CircuitProtectionDeviceType,
  FuseUtilizationCategory,
  RcdType,
} from "../../shared/constants/protection-device.js";
import type { SerializedProjectCommand } from "./project-command.model.js";

export const circuitProtectionUpdateCommandType =
  "circuit-protection.update" as const;
export const circuitProtectionUpdateCommandSchemaVersion = 1 as const;

// type "NONE" records an explicit "no protection device" decision; all
// values are then null. A missing snapshot (null) means "not yet planned".
export interface CircuitProtectionSnapshot {
  circuitId: string;
  type: CircuitProtectionDeviceType;
  ratedCurrentA: number | null;
  fuseUtilizationCategory: FuseUtilizationCategory | null;
  tripCharacteristic: BreakerTripCharacteristic | null;
  rcdType: RcdType | null;
  ratedResidualCurrentMa: number | null;
}

interface CircuitProtectionUpdatePayload {
  circuitId: string;
  expected: CircuitProtectionSnapshot | null;
  target: CircuitProtectionSnapshot | null;
}

export interface CircuitProtectionUpdateProjectCommand
  extends SerializedProjectCommand<CircuitProtectionUpdatePayload> {
  schemaVersion: typeof circuitProtectionUpdateCommandSchemaVersion;
  type: typeof circuitProtectionUpdateCommandType;
}

export function createCircuitProtectionUpdateProjectCommand(
  circuitId: string,
  expected: CircuitProtectionSnapshot | null,
  target: CircuitProtectionSnapshot | null
): CircuitProtectionUpdateProjectCommand {
  const command: CircuitProtectionUpdateProjectCommand = {
    schemaVersion: circuitProtectionUpdateCommandSchemaVersion,
    type: circuitProtectionUpdateCommandType,
    payload: { circuitId, expected, target },
  };
  assertCircuitProtectionUpdateProjectCommand(command);
  return command;
}

export function assertCircuitProtectionUpdateProjectCommand(
  command: SerializedProjectCommand<unknown>
): asserts command is CircuitProtectionUpdateProjectCommand {
  if (
    command.schemaVersion !== circuitProtectionUpdateCommandSchemaVersion ||
    command.type !== circuitProtectionUpdateCommandType ||
    !isPlainObject(command.payload) ||
    Object.keys(command.payload).length !== 3
  ) {
    throw new Error("Unsupported circuit-protection update command.");
  }
  const { circuitId, expected, target } = command.payload;
  if (typeof circuitId !== "string" || !circuitId.trim()) {
    throw new Error("Circuit protection requires a circuit id.");
  }
  if (expected === null && target === null) {
    throw new Error("Circuit protection update must change state.");
  }
  if (expected !== null) {
    assertCircuitProtectionSnapshot(expected, circuitId);
  }
  if (target !== null) {
    assertCircuitProtectionSnapshot(target, circuitId);
  }
  if (circuitProtectionSnapshotsEqual(expected, target)) {
    throw new Error("Circuit protection update must change state.");
  }
}

function circuitProtectionSnapshotsEqual(
  left: CircuitProtectionSnapshot | null,
  right: CircuitProtectionSnapshot | null
): boolean {
  if (left === null || right === null) {
    return left === right;
  }
  return (
    left.circuitId === right.circuitId &&
    left.type === right.type &&
    left.ratedCurrentA === right.ratedCurrentA &&
    left.fuseUtilizationCategory === right.fuseUtilizationCategory &&
    left.tripCharacteristic === right.tripCharacteristic &&
    left.rcdType === right.rcdType &&
    left.ratedResidualCurrentMa === right.ratedResidualCurrentMa
  );
}

export function assertCircuitProtectionSnapshot(
  value: unknown,
  circuitId: string
): asserts value is CircuitProtectionSnapshot {
  if (
    !isPlainObject(value) ||
    Object.keys(value).length !== 7 ||
    value.circuitId !== circuitId
  ) {
    throw new Error("Circuit-protection snapshot is invalid.");
  }
  if (!isValidCircuitProtectionRecord(value)) {
    throw new Error("Circuit-protection configuration is invalid.");
  }
}

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