import { stableStringify } from "@add-ideas/toolbox-helpers";
import {
  MAX_TESTS,
  byteLength,
  minimizeInput,
  type FailurePredicate,
  type InputStructure,
  type PredicateStability,
  type ReductionStep,
} from "./engine";

export const MAX_BUNDLE_FILES = 100;
export const MAX_BUNDLE_BYTES = 4 * 1024 * 1024;

export interface BundleFile {
  path: string;
  content: string;
  structure?: InputStructure;
}

export interface BundleMinimizeOptions {
  maxTests: number;
  maxSeconds: number;
  stability?: PredicateStability;
}

export type BundlePredicate = (
  files: readonly BundleFile[],
  signal: AbortSignal,
) => boolean | Promise<boolean>;

export interface BundleReductionStep {
  stage: "files" | "content";
  path?: string;
  beforeFiles: number;
  afterFiles: number;
  beforeBytes: number;
  afterBytes: number;
  test: number;
  contentStep?: ReductionStep["stage"];
}

export interface BundleMinimizeResult {
  version: "bundle-ddmin-v1";
  original: BundleFile[];
  minimized: BundleFile[];
  tests: number;
  accepted: number;
  exhausted: boolean;
  stability: PredicateStability;
  unstableCandidates: number;
  steps: BundleReductionStep[];
}

export interface BundleAdapterProfile {
  id: "json-map" | "concatenated" | "primary-file";
  label: string;
  description: string;
  adapt(files: readonly BundleFile[]): string;
}

export const BUNDLE_ADAPTER_PROFILES: readonly BundleAdapterProfile[] = [
  {
    id: "json-map",
    label: "JSON path map",
    description: "Presents a deterministic path-to-content JSON object.",
    adapt: (files) =>
      stableStringify(
        Object.fromEntries(files.map((file) => [file.path, file.content])),
      ),
  },
  {
    id: "concatenated",
    label: "Delimited concatenation",
    description:
      "Presents all files with explicit, deterministic path markers.",
    adapt: (files) =>
      files
        .map((file) => `\n--- toolbox-file:${file.path} ---\n${file.content}`)
        .join(""),
  },
  {
    id: "primary-file",
    label: "Primary file",
    description: "Presents only the lexicographically first retained file.",
    adapt: (files) => files[0]?.content ?? "",
  },
];

export function bundlePredicateAdapter(
  predicate: FailurePredicate,
  profileId: BundleAdapterProfile["id"],
): BundlePredicate {
  const profile = BUNDLE_ADAPTER_PROFILES.find((item) => item.id === profileId);
  if (!profile) throw new TypeError(`Unknown bundle adapter ${profileId}.`);
  return (files, signal) => predicate(profile.adapt(files), signal);
}

export async function minimizeBundle(
  input: readonly BundleFile[],
  options: BundleMinimizeOptions,
  predicate: BundlePredicate,
  signal: AbortSignal,
): Promise<BundleMinimizeResult> {
  const original = normalizeBundle(input);
  if (
    !Number.isInteger(options.maxTests) ||
    options.maxTests < 1 ||
    options.maxTests > MAX_TESTS
  )
    throw new RangeError(`Bundle test budget must be 1–${MAX_TESTS}.`);
  if (
    !Number.isFinite(options.maxSeconds) ||
    options.maxSeconds <= 0 ||
    options.maxSeconds > 30
  )
    throw new RangeError(
      "Bundle time budget must be above 0 and at most 30 seconds.",
    );
  const stability = options.stability ?? { samples: 1, requiredPasses: 1 };
  if (
    !Number.isInteger(stability.samples) ||
    stability.samples < 1 ||
    stability.samples > 9 ||
    !Number.isInteger(stability.requiredPasses) ||
    stability.requiredPasses < 1 ||
    stability.requiredPasses > stability.samples
  )
    throw new RangeError("Bundle stability settings are invalid.");
  const deadline = Date.now() + options.maxSeconds * 1_000;
  let tests = 0;
  let accepted = 0;
  let exhausted = false;
  let unstableCandidates = 0;
  let current = original.map((file) => ({ ...file }));
  const steps: BundleReductionStep[] = [];
  const evaluate = async (candidate: readonly BundleFile[]) => {
    let passes = 0;
    let observations = 0;
    while (observations < stability.samples) {
      signal.throwIfAborted();
      if (tests >= options.maxTests || Date.now() >= deadline) {
        exhausted = true;
        return false;
      }
      tests += 1;
      if (await predicate(candidate, signal)) passes += 1;
      observations += 1;
    }
    if (passes > 0 && passes < observations) unstableCandidates += 1;
    return passes >= stability.requiredPasses;
  };
  if (!(await evaluate(current)))
    throw new TypeError(
      "The original bundle does not stably satisfy the selected predicate.",
    );

  let granularity = 2;
  while (current.length && !exhausted) {
    const chunk = Math.ceil(current.length / granularity);
    let changed = false;
    for (let start = 0; start < current.length; start += chunk) {
      const candidate = current
        .slice(0, start)
        .concat(current.slice(start + chunk));
      if (await evaluate(candidate)) {
        const before = bundleBytes(current);
        const beforeFiles = current.length;
        current = candidate;
        accepted += 1;
        steps.push({
          stage: "files",
          beforeFiles,
          afterFiles: current.length,
          beforeBytes: before,
          afterBytes: bundleBytes(current),
          test: tests,
        });
        granularity = Math.max(2, granularity - 1);
        changed = true;
        break;
      }
      if (exhausted) break;
    }
    if (!changed) {
      if (granularity >= current.length) break;
      granularity = Math.min(current.length, granularity * 2);
    }
  }

  for (let index = 0; index < current.length && !exhausted; index += 1) {
    const remainingTests = options.maxTests - tests;
    const remainingSeconds = (deadline - Date.now()) / 1_000;
    if (remainingTests < 1 || remainingSeconds <= 0) {
      exhausted = true;
      break;
    }
    const file = current[index]!;
    const result = await minimizeInput(
      file.content,
      {
        structure: file.structure ?? inferStructure(file.path),
        maxTests: remainingTests,
        maxSeconds: Math.min(30, remainingSeconds),
        stability,
      },
      (candidate, childSignal) =>
        predicate(
          current.map((entry, candidateIndex) =>
            candidateIndex === index ? { ...entry, content: candidate } : entry,
          ),
          childSignal,
        ),
      signal,
    );
    tests += result.tests;
    exhausted ||= result.exhausted;
    if (result.minimized !== file.content) {
      const before = bundleBytes(current);
      current[index] = { ...file, content: result.minimized };
      accepted += result.accepted;
      for (const contentStep of result.steps)
        steps.push({
          stage: "content",
          path: file.path,
          beforeFiles: current.length,
          afterFiles: current.length,
          beforeBytes: before,
          afterBytes: bundleBytes(current),
          test: tests - result.tests + contentStep.test,
          contentStep: contentStep.stage,
        });
    }
  }
  return {
    version: "bundle-ddmin-v1",
    original,
    minimized: current,
    tests,
    accepted,
    exhausted,
    stability,
    unstableCandidates,
    steps,
  };
}

function normalizeBundle(input: readonly BundleFile[]): BundleFile[] {
  if (!input.length) throw new TypeError("A bundle needs at least one file.");
  if (input.length > MAX_BUNDLE_FILES)
    throw new RangeError(`Bundles are limited to ${MAX_BUNDLE_FILES} files.`);
  const paths = new Set<string>();
  const result = input.map((file) => {
    const path = normalizePath(file.path);
    if (paths.has(path)) throw new TypeError(`Duplicate bundle path ${path}.`);
    paths.add(path);
    if (byteLength(file.content) > 2 * 1024 * 1024)
      throw new RangeError(`${path} exceeds the 2 MiB per-file limit.`);
    return {
      path,
      content: file.content,
      ...(file.structure ? { structure: file.structure } : {}),
    };
  });
  result.sort((left, right) =>
    left.path < right.path ? -1 : left.path > right.path ? 1 : 0,
  );
  if (bundleBytes(result) > MAX_BUNDLE_BYTES)
    throw new RangeError("Bundle contents exceed 4 MiB.");
  return result;
}

function normalizePath(path: string): string {
  const normalized = path.normalize("NFC");
  if (
    !normalized ||
    normalized.includes("\\") ||
    normalized.startsWith("/") ||
    normalized.split("/").some((part) => !part || part === "." || part === "..")
  )
    throw new TypeError(`Unsafe bundle path ${path}.`);
  return normalized;
}

function bundleBytes(files: readonly BundleFile[]): number {
  return files.reduce((sum, file) => sum + byteLength(file.content), 0);
}

function inferStructure(path: string): InputStructure {
  const lower = path.toLowerCase();
  return lower.endsWith(".json")
    ? "json"
    : lower.endsWith(".xml")
      ? "xml"
      : "text";
}