import type { ErrorCode } from "./error";

export const OOM_RECOVERY_REPORT_SCHEMA = 1 as const;

export const OOM_RECOVERY_SCENARIOS = [
  "WASM_MAIN",
  "OPFS_STAGING",
  "GPU_RESOURCES",
  "NANOVDB_RESIDENT",
] as const;

export type OOMRecoveryScenario = typeof OOM_RECOVERY_SCENARIOS[number];

export const OOM_FAULT_POINTS = [
  "WASM_MAIN_OPEN_INPUT",
  "WASM_MAIN_EDIT_COMMAND",
  "WASM_MAIN_SAVE_RESULT",
  "OPFS_STAGING_WRITE",
  "GPU_GEOMETRY_UPLOAD",
  "GPU_TEXTURE_UPLOAD",
  "NANOVDB_RESIDENT_BUFFER",
  "NANOVDB_PAGE_TABLE",
] as const;

export type OOMFaultPoint = typeof OOM_FAULT_POINTS[number];

export const OOM_FAULT_ERROR: Record<OOMFaultPoint, { code: ErrorCode; stage: string }> = {
  WASM_MAIN_OPEN_INPUT: { code: "WASM_OUT_OF_MEMORY", stage: "WASM_OPEN_INPUT" },
  WASM_MAIN_EDIT_COMMAND: { code: "WASM_OUT_OF_MEMORY", stage: "MAIN_EDIT_COMMAND" },
  WASM_MAIN_SAVE_RESULT: { code: "WASM_OUT_OF_MEMORY", stage: "WASM_SAVE_RESULT" },
  OPFS_STAGING_WRITE: { code: "STORAGE_QUOTA", stage: "OPFS_STAGING_WRITE" },
  GPU_GEOMETRY_UPLOAD: { code: "GPU_GEOMETRY_BUDGET_EXCEEDED", stage: "GPU_GEOMETRY_UPLOAD" },
  GPU_TEXTURE_UPLOAD: { code: "GPU_TEXTURE_BUDGET_EXCEEDED", stage: "GPU_TEXTURE_UPLOAD" },
  NANOVDB_RESIDENT_BUFFER: { code: "NANOVDB_GPU_BUDGET_EXCEEDED", stage: "NANOVDB_RESIDENT_BUFFER" },
  NANOVDB_PAGE_TABLE: { code: "NANOVDB_GPU_BUDGET_EXCEEDED", stage: "NANOVDB_PAGE_TABLE" },
};

export interface OOMFaultObservationIR {
  point: OOMFaultPoint;
  code: ErrorCode;
  stage: string;
  attemptedBytes: number;
  allocationCount: number;
  failAfterBytes?: number;
  failAfterCount?: number;
}

export interface OOMMemoryReportIR {
  beforeBytes: number;
  peakBytes: number;
  afterBytes: number;
  releasedBytes: number;
}

export interface OOMStateReportIR {
  revisionBefore: number;
  revisionAfter: number;
  hashBefore?: string;
  hashAfter?: string;
  temporaryResourcesBefore: number;
  temporaryResourcesPeak: number;
  temporaryResourcesAfter: number;
}

export interface OOMRecoveryReportIR {
  schemaVersion: typeof OOM_RECOVERY_REPORT_SCHEMA;
  scenario: OOMRecoveryScenario;
  faults: OOMFaultObservationIR[];
  memory: OOMMemoryReportIR;
  state: OOMStateReportIR;
  recovery: {
    recovered: boolean;
    sameSession: boolean;
    restartedSession: boolean;
    tokenIsolated: boolean;
  };
  checks: string[];
}

const SHA256 = /^[a-f0-9]{64}$/;

function record(value: unknown, label: string): Record<string, unknown> {
  if (!value || typeof value !== "object" || Array.isArray(value)) throw new Error(`OOM_REPORT_INVALID: ${label}`);
  return value as Record<string, unknown>;
}

function integer(value: unknown, label: string): number {
  if (!Number.isSafeInteger(value) || (value as number) < 0) throw new Error(`OOM_REPORT_INVALID: ${label}`);
  return value as number;
}

export function parseOOMRecoveryReport(value: unknown): OOMRecoveryReportIR {
  const source = record(value, "report must be an object");
  if (source.schemaVersion !== OOM_RECOVERY_REPORT_SCHEMA || !OOM_RECOVERY_SCENARIOS.includes(source.scenario as OOMRecoveryScenario)) {
    throw new Error("OOM_REPORT_INVALID: schema or scenario");
  }
  if (!Array.isArray(source.faults) || source.faults.length === 0) throw new Error("OOM_REPORT_INVALID: faults");
  const faults = source.faults.map((candidate, index): OOMFaultObservationIR => {
    const fault = record(candidate, `fault ${index}`);
    const point = fault.point as OOMFaultPoint;
    if (!OOM_FAULT_POINTS.includes(point)) throw new Error(`OOM_REPORT_INVALID: fault ${index} point`);
    const expected = OOM_FAULT_ERROR[point];
    if (fault.code !== expected.code || fault.stage !== expected.stage) throw new Error(`OOM_REPORT_INVALID: fault ${index} mapping`);
    const parsed: OOMFaultObservationIR = {
      point,
      code: expected.code,
      stage: expected.stage,
      attemptedBytes: integer(fault.attemptedBytes, `fault ${index} attemptedBytes`),
      allocationCount: integer(fault.allocationCount, `fault ${index} allocationCount`),
    };
    if (fault.failAfterBytes !== undefined) parsed.failAfterBytes = integer(fault.failAfterBytes, `fault ${index} failAfterBytes`);
    if (fault.failAfterCount !== undefined) parsed.failAfterCount = integer(fault.failAfterCount, `fault ${index} failAfterCount`);
    if (parsed.failAfterBytes === undefined && parsed.failAfterCount === undefined) throw new Error(`OOM_REPORT_INVALID: fault ${index} threshold`);
    return parsed;
  });

  const rawMemory = record(source.memory, "memory");
  const memory: OOMMemoryReportIR = {
    beforeBytes: integer(rawMemory.beforeBytes, "memory.beforeBytes"),
    peakBytes: integer(rawMemory.peakBytes, "memory.peakBytes"),
    afterBytes: integer(rawMemory.afterBytes, "memory.afterBytes"),
    releasedBytes: integer(rawMemory.releasedBytes, "memory.releasedBytes"),
  };
  if (memory.peakBytes < memory.beforeBytes || memory.peakBytes < memory.afterBytes) throw new Error("OOM_REPORT_INVALID: memory peak");

  const rawState = record(source.state, "state");
  const state: OOMStateReportIR = {
    revisionBefore: integer(rawState.revisionBefore, "state.revisionBefore"),
    revisionAfter: integer(rawState.revisionAfter, "state.revisionAfter"),
    temporaryResourcesBefore: integer(rawState.temporaryResourcesBefore, "state.temporaryResourcesBefore"),
    temporaryResourcesPeak: integer(rawState.temporaryResourcesPeak, "state.temporaryResourcesPeak"),
    temporaryResourcesAfter: integer(rawState.temporaryResourcesAfter, "state.temporaryResourcesAfter"),
  };
  if (rawState.hashBefore !== undefined) {
    if (typeof rawState.hashBefore !== "string" || !SHA256.test(rawState.hashBefore)) throw new Error("OOM_REPORT_INVALID: state.hashBefore");
    state.hashBefore = rawState.hashBefore;
  }
  if (rawState.hashAfter !== undefined) {
    if (typeof rawState.hashAfter !== "string" || !SHA256.test(rawState.hashAfter)) throw new Error("OOM_REPORT_INVALID: state.hashAfter");
    state.hashAfter = rawState.hashAfter;
  }
  if ((state.hashBefore === undefined) !== (state.hashAfter === undefined)) throw new Error("OOM_REPORT_INVALID: state hashes must be paired");
  if (state.temporaryResourcesPeak < state.temporaryResourcesBefore || state.temporaryResourcesPeak < state.temporaryResourcesAfter) {
    throw new Error("OOM_REPORT_INVALID: temporary resource peak");
  }

  const rawRecovery = record(source.recovery, "recovery");
  const recovery = {
    recovered: rawRecovery.recovered,
    sameSession: rawRecovery.sameSession,
    restartedSession: rawRecovery.restartedSession,
    tokenIsolated: rawRecovery.tokenIsolated,
  };
  if (Object.values(recovery).some((candidate) => typeof candidate !== "boolean") || !recovery.recovered || !recovery.tokenIsolated || (!recovery.sameSession && !recovery.restartedSession)) {
    throw new Error("OOM_REPORT_INVALID: recovery");
  }
  if (!Array.isArray(source.checks) || source.checks.length === 0 || source.checks.some((check) => typeof check !== "string" || check.length === 0)) {
    throw new Error("OOM_REPORT_INVALID: checks");
  }

  return { schemaVersion: OOM_RECOVERY_REPORT_SCHEMA, scenario: source.scenario as OOMRecoveryScenario, faults, memory, state, recovery: recovery as OOMRecoveryReportIR["recovery"], checks: [...new Set(source.checks as string[])] };
}

export function parseOOMRecoverySuite(value: unknown): OOMRecoveryReportIR[] {
  if (!Array.isArray(value)) throw new Error("OOM_REPORT_INVALID: suite");
  const reports = value.map(parseOOMRecoveryReport);
  if (reports.length !== OOM_RECOVERY_SCENARIOS.length || new Set(reports.map((report) => report.scenario)).size !== OOM_RECOVERY_SCENARIOS.length) {
    throw new Error("OOM_REPORT_INVALID: suite must contain each scenario exactly once");
  }
  for (const scenario of OOM_RECOVERY_SCENARIOS) if (!reports.some((report) => report.scenario === scenario)) throw new Error(`OOM_REPORT_INVALID: missing ${scenario}`);
  return reports;
}