import { generateSchemaSample, resolveLocalReference } from "./refs";
import type {
  ApiDocument,
  JsonObject,
  JsonValue,
  LocalWorkspace,
  ValidationProblem,
} from "./types";

export interface AsyncMessageExample {
  id: string;
  name?: string;
  contentType?: string;
  payload?: JsonValue;
  headers?: JsonValue;
  notices: string[];
}

export interface AsyncOperation {
  key: string;
  operationId: string;
  action: "send" | "receive" | "publish" | "subscribe";
  channelId: string;
  address: string;
  title?: string;
  summary?: string;
  protocols: string[];
  messages: AsyncMessageExample[];
}

interface ResolvedObject {
  value: JsonObject;
  filename: string;
  key?: string;
}

function asObject(value: JsonValue | undefined): JsonObject | undefined {
  return value && typeof value === "object" && !Array.isArray(value)
    ? value
    : undefined;
}

function resolveObject(
  workspace: LocalWorkspace,
  raw: JsonValue | undefined,
  filename = workspace.entry,
  depth = 0,
): ResolvedObject | undefined {
  const value = asObject(raw);
  if (!value) return undefined;
  if (typeof value.$ref !== "string") return { value, filename };
  if (depth > 20)
    throw new RangeError("AsyncAPI reference chain exceeds 20 links.");
  const resolved = resolveLocalReference(workspace, value.$ref, filename);
  const object = resolveObject(
    workspace,
    resolved.value,
    resolved.document.filename,
    depth + 1,
  );
  return object ? { ...object, key: resolved.key } : undefined;
}

function scanReferences(root: JsonValue): string[] {
  const references: string[] = [];
  const stack: Array<{ value: JsonValue; depth: number }> = [
    { value: root, depth: 0 },
  ];
  let nodes = 0;
  while (stack.length) {
    const current = stack.pop()!;
    nodes += 1;
    if (nodes > 100_000 || current.depth > 64) break;
    if (Array.isArray(current.value))
      for (const child of current.value)
        stack.push({ value: child, depth: current.depth + 1 });
    else {
      const object = asObject(current.value);
      if (!object) continue;
      for (const [key, child] of Object.entries(object))
        if (key === "$ref" && typeof child === "string") references.push(child);
        else stack.push({ value: child, depth: current.depth + 1 });
    }
  }
  return references;
}

export function validateAsyncApi(document: ApiDocument): ValidationProblem[] {
  const root = document.value;
  const problems: ValidationProblem[] = [];
  const version = typeof root.asyncapi === "string" ? root.asyncapi : undefined;
  if (!version)
    problems.push({
      level: "error",
      path: "/asyncapi",
      message: "Missing AsyncAPI version string.",
    });
  else if (!/^(?:2\.[0-6]\.\d+|3\.[01]\.\d+)$/u.test(version))
    problems.push({
      level: "error",
      path: "/asyncapi",
      message: `Version “${version}” is outside the focused AsyncAPI 2.0–2.6 and 3.0/3.1 families.`,
    });
  const info = asObject(root.info);
  if (
    !info ||
    typeof info.title !== "string" ||
    !info.title.trim() ||
    typeof info.version !== "string" ||
    !info.version.trim()
  )
    problems.push({
      level: "error",
      path: "/info",
      message: "AsyncAPI info needs non-empty title and version strings.",
    });
  const channels = asObject(root.channels);
  if (!channels)
    problems.push({
      level: "error",
      path: "/channels",
      message: "Missing channels object.",
    });
  else if (!Object.keys(channels).length)
    problems.push({
      level: "warning",
      path: "/channels",
      message: "No channels are declared.",
    });
  if (/^3\./u.test(version ?? "") && !asObject(root.operations))
    problems.push({
      level: "warning",
      path: "/operations",
      message: "No root operations are declared.",
    });
  for (const reference of scanReferences(root))
    if (
      /^[a-z][a-z0-9+.-]*:/iu.test(reference) ||
      reference.startsWith("//") ||
      reference.startsWith("/")
    )
      problems.push({
        level: "error",
        path: "/$ref",
        message: `Remote or absolute reference is prohibited: ${reference}`,
      });
  if (!problems.some((item) => item.level === "error"))
    problems.unshift({
      level: "info",
      path: "/",
      message: `Focused structural checks passed for AsyncAPI ${version}.`,
    });
  return problems.slice(0, 1_000);
}

function protocolInventory(root: JsonObject): string[] {
  const servers = asObject(root.servers) ?? {};
  return [
    ...new Set(
      Object.values(servers).flatMap((raw) => {
        const server = asObject(raw);
        return typeof server?.protocol === "string" ? [server.protocol] : [];
      }),
    ),
  ].slice(0, 100);
}

function messageExample(
  workspace: LocalWorkspace,
  id: string,
  raw: JsonValue,
  filename: string,
  defaultContentType?: string,
): AsyncMessageExample {
  const notices: string[] = [];
  try {
    const resolved = resolveObject(workspace, raw, filename);
    if (!resolved)
      return { id, notices: ["Message is not an object or local reference."] };
    const message = resolved.value;
    const examples = Array.isArray(message.examples) ? message.examples : [];
    const firstExample = asObject(examples[0]);
    const derive = (schema: JsonValue | undefined, label: string) => {
      if (schema === undefined) return undefined;
      try {
        const generated = generateSchemaSample(
          workspace,
          schema,
          resolved.filename,
        );
        notices.push(
          ...generated.notices.map((notice) => `${label}: ${notice}`),
        );
        return generated.value;
      } catch (reason) {
        notices.push(
          `${label}: ${reason instanceof Error ? reason.message : "sample generation failed"}.`,
        );
        return undefined;
      }
    };
    return {
      id,
      name: typeof message.name === "string" ? message.name : undefined,
      contentType:
        typeof message.contentType === "string"
          ? message.contentType
          : defaultContentType,
      payload:
        firstExample?.payload ?? derive(message.payload, "Payload sample"),
      headers:
        firstExample?.headers ?? derive(message.headers, "Header sample"),
      notices: [...new Set(notices)],
    };
  } catch (reason) {
    return {
      id,
      notices: [
        reason instanceof Error ? reason.message : "Message reference failed.",
      ],
    };
  }
}

function channelIdFromReference(reference: string): string {
  const match = /#\/channels\/([^/]+)$/u.exec(reference);
  if (!match) return reference;
  try {
    return decodeURIComponent(
      match[1]!.replaceAll("~1", "/").replaceAll("~0", "~"),
    );
  } catch {
    return match[1]!;
  }
}

export function collectAsyncOperations(
  workspace: LocalWorkspace,
): AsyncOperation[] {
  const root = workspace.documents.get(workspace.entry)?.value;
  if (!root) throw new ReferenceError("AsyncAPI entry document is missing.");
  const version = String(root.asyncapi ?? "");
  const channels = asObject(root.channels) ?? {};
  const defaultContentType =
    typeof root.defaultContentType === "string"
      ? root.defaultContentType
      : undefined;
  const protocols = protocolInventory(root);
  const output: AsyncOperation[] = [];
  if (/^3\./u.test(version)) {
    const operations = asObject(root.operations) ?? {};
    for (const [operationId, rawOperation] of Object.entries(operations)) {
      if (output.length >= 2_000)
        throw new RangeError("AsyncAPI operation count exceeds 2,000.");
      try {
        const resolvedOperation = resolveObject(workspace, rawOperation);
        const operation = resolvedOperation?.value;
        const action = operation?.action;
        const channelReference = asObject(operation?.channel)?.$ref;
        if (
          (action !== "send" && action !== "receive") ||
          typeof channelReference !== "string"
        )
          continue;
        const resolvedChannel = resolveObject(
          workspace,
          operation!.channel,
          resolvedOperation?.filename,
        );
        const channel = resolvedChannel?.value;
        if (!channel) continue;
        const channelId = channelIdFromReference(channelReference);
        const selectedMessages = Array.isArray(operation!.messages)
          ? operation!.messages.map(
              (raw, index) => [`message-${index + 1}`, raw] as const,
            )
          : Object.entries(asObject(channel.messages) ?? {});
        const messages = selectedMessages
          .slice(0, 100)
          .map(([id, raw]) =>
            messageExample(
              workspace,
              id,
              raw,
              resolvedChannel.filename,
              defaultContentType,
            ),
          );
        const address =
          typeof channel.address === "string"
            ? channel.address
            : "(dynamic/unknown)";
        output.push({
          key: `${action.toUpperCase()} ${address} · ${operationId}`,
          operationId,
          action,
          channelId,
          address,
          title:
            typeof operation!.title === "string" ? operation!.title : undefined,
          summary:
            typeof operation!.summary === "string"
              ? operation!.summary
              : typeof channel.summary === "string"
                ? channel.summary
                : undefined,
          protocols,
          messages,
        });
      } catch {
        // The validation report inventories blocked/unresolved references. A
        // single invalid operation must not hide other usable operations.
      }
    }
  } else {
    for (const [channelId, rawChannel] of Object.entries(channels)) {
      const resolvedChannel = resolveObject(workspace, rawChannel);
      const channel = resolvedChannel?.value;
      if (!channel) continue;
      for (const action of ["publish", "subscribe"] as const) {
        const operation = asObject(channel[action]);
        if (!operation) continue;
        if (output.length >= 2_000)
          throw new RangeError("AsyncAPI operation count exceeds 2,000.");
        const rawMessages = Array.isArray(operation.message)
          ? operation.message
          : asObject(operation.message)?.oneOf &&
              Array.isArray(asObject(operation.message)?.oneOf)
            ? (asObject(operation.message)!.oneOf as JsonValue[])
            : operation.message !== undefined
              ? [operation.message]
              : [];
        const messages = rawMessages
          .slice(0, 100)
          .map((raw, index) =>
            messageExample(
              workspace,
              `message-${index + 1}`,
              raw,
              resolvedChannel.filename,
              defaultContentType,
            ),
          );
        const address = channelId;
        output.push({
          key: `${action.toUpperCase()} ${address}`,
          operationId:
            typeof operation.operationId === "string"
              ? operation.operationId
              : `${action}-${channelId}`,
          action,
          channelId,
          address,
          summary:
            typeof operation.summary === "string"
              ? operation.summary
              : undefined,
          protocols,
          messages,
        });
      }
    }
  }
  return output;
}