/**
 * Azure DNS adapter — uses the Azure Resource Manager REST API.
 * Requires config: tenantId, clientId, clientSecret, subscriptionId
 *
 * The service principal needs the "DNS Zone Contributor" role (or higher)
 * on the subscription or resource group containing the DNS zones.
 *
 * Zone IDs are encoded as "resourceGroup::zoneName" so we know which
 * resource group to target for record operations.
 */
import type { DnsAdapter, DnsRecord, DnsRecordInput, DnsZone } from "../types.js";
import { withDiagLogging } from "../../services/diagLog.js";

const ARM_BASE = "https://management.azure.com";
const API_VERSION = "2018-05-01";

export interface AzureConfig {
  tenantId: string;
  clientId: string;
  clientSecret: string;
  subscriptionId: string;
}

export function createAzureAdapter(config: AzureConfig): DnsAdapter {
  let tokenCache: { token: string; expiresAt: number } | null = null;

  async function getToken(): Promise<string> {
    if (tokenCache && tokenCache.expiresAt > Date.now() + 60_000) return tokenCache.token;

    const url = `https://login.microsoftonline.com/${config.tenantId}/oauth2/v2.0/token`;
    const body = new URLSearchParams({
      grant_type: "client_credentials",
      client_id: config.clientId,
      client_secret: config.clientSecret,
      scope: "https://management.azure.com/.default",
    });

    const res = await fetch(url, { method: "POST", body });
    const data = await res.json();

    if (!res.ok || data.error) {
      throw new Error(`Azure auth failed: ${data.error_description ?? data.error ?? res.statusText}`);
    }

    tokenCache = { token: data.access_token, expiresAt: Date.now() + data.expires_in * 1000 };
    return tokenCache.token;
  }

  async function armFetch(path: string, options: RequestInit = {}): Promise<any> {
    const token = await getToken();
    const url = `${ARM_BASE}${path}${path.includes("?") ? "&" : "?"}api-version=${API_VERSION}`;

    const res = await fetch(url, {
      ...options,
      headers: {
        Authorization: `Bearer ${token}`,
        "Content-Type": "application/json",
        ...(options.headers as Record<string, string> | undefined),
      },
    });

    if (res.status === 204) return null;
    const text = await res.text();
    if (!text || !text.trim()) return null;

    let data;
    try {
      data = JSON.parse(text);
    } catch {
      throw new Error(`Azure returned non-JSON response (HTTP ${res.status}): ${text.slice(0, 200)}`);
    }

    if (!res.ok) {
      throw new Error(data?.error?.message ?? `Azure API error ${res.status}`);
    }
    return data;
  }

  function encodeZoneId(resourceGroup: string, zoneName: string) {
    return `${resourceGroup}::${zoneName}`;
  }

  function decodeZoneId(zoneId: string) {
    const idx = zoneId.indexOf("::");
    return { resourceGroup: zoneId.slice(0, idx), zoneName: zoneId.slice(idx + 2) };
  }

  async function listZones(): Promise<DnsZone[]> {
    const data = await armFetch(
      `/subscriptions/${config.subscriptionId}/providers/Microsoft.Network/dnsZones`,
    );
    return (data.value ?? []).map((z: any) => {
      const rgMatch = z.id.match(/resourceGroups\/([^/]+)\//i);
      const rg = rgMatch ? rgMatch[1] : "unknown";
      return { id: encodeZoneId(rg, z.name), name: z.name };
    });
  }

  function extractRecords(type: string, props: any): string[] {
    switch (type) {
      case "A":
        return (props.ARecords ?? []).map((r: any) => r.ipv4Address);
      case "AAAA":
        return (props.AAAARecords ?? []).map((r: any) => r.ipv6Address);
      case "CNAME":
        return props.CNAMERecord ? [props.CNAMERecord.cname] : [];
      case "MX":
        return (props.MXRecords ?? []).map((r: any) => r.exchange);
      case "NS":
        return (props.NSRecords ?? []).map((r: any) => r.nsdname);
      case "TXT":
        return (props.TXTRecords ?? []).map((r: any) => r.value.join(""));
      case "SRV":
        return (props.SRVRecords ?? []).map((r: any) => `${r.priority} ${r.weight} ${r.port} ${r.target}`);
      case "CAA":
        return (props.caaRecords ?? []).map((r: any) => `${r.flags} ${r.tag} ${r.value}`);
      case "PTR":
        return (props.PTRRecords ?? []).map((r: any) => r.ptrdname);
      default:
        return [];
    }
  }

  function extractMxPriority(props: any): number | null {
    return props.MXRecords?.[0]?.preference ?? null;
  }

  async function listRecords(zoneId: string): Promise<DnsRecord[]> {
    const { resourceGroup, zoneName } = decodeZoneId(zoneId);
    const path = `/subscriptions/${config.subscriptionId}/resourceGroups/${resourceGroup}/providers/Microsoft.Network/dnsZones/${zoneName}/recordSets`;
    const data = await armFetch(path);

    const records: DnsRecord[] = [];
    for (const rs of data.value ?? []) {
      const type = rs.type.split("/").pop();
      const name = rs.name === "@" ? zoneName : `${rs.name}.${zoneName}`;
      const ttl = rs.properties.TTL;
      const entries = extractRecords(type, rs.properties);
      for (const content of entries) {
        records.push({
          id: `${rs.name}::${type}::${content}`,
          type,
          name,
          content,
          ttl,
          priority: type === "MX" ? extractMxPriority(rs.properties) : null,
        });
      }
    }
    return records;
  }

  function appendToRecordSet(props: any, type: string, content: string, priority?: number) {
    switch (type) {
      case "A":
        props.ARecords = [...(props.ARecords ?? []), { ipv4Address: content }];
        break;
      case "AAAA":
        props.AAAARecords = [...(props.AAAARecords ?? []), { ipv6Address: content }];
        break;
      case "CNAME":
        props.CNAMERecord = { cname: content };
        break;
      case "MX":
        props.MXRecords = [...(props.MXRecords ?? []), { preference: Number(priority) || 10, exchange: content }];
        break;
      case "NS":
        props.NSRecords = [...(props.NSRecords ?? []), { nsdname: content }];
        break;
      case "TXT":
        props.TXTRecords = [...(props.TXTRecords ?? []), { value: [content] }];
        break;
      case "PTR":
        props.PTRRecords = [...(props.PTRRecords ?? []), { ptrdname: content }];
        break;
      default:
        throw new Error(`Record type ${type} is not supported for add via this adapter`);
    }
  }

  function removeFromRecordSet(props: any, type: string, content: string) {
    switch (type) {
      case "A":
        props.ARecords = (props.ARecords ?? []).filter((r: any) => r.ipv4Address !== content);
        break;
      case "AAAA":
        props.AAAARecords = (props.AAAARecords ?? []).filter((r: any) => r.ipv6Address !== content);
        break;
      case "CNAME":
        props.CNAMERecord = null;
        break;
      case "MX":
        props.MXRecords = (props.MXRecords ?? []).filter((r: any) => r.exchange !== content);
        break;
      case "NS":
        props.NSRecords = (props.NSRecords ?? []).filter((r: any) => r.nsdname !== content);
        break;
      case "TXT":
        props.TXTRecords = (props.TXTRecords ?? []).filter((r: any) => r.value.join("") !== content);
        break;
      case "PTR":
        props.PTRRecords = (props.PTRRecords ?? []).filter((r: any) => r.ptrdname !== content);
        break;
    }
  }

  function countRecords(props: any, type: string): number {
    switch (type) {
      case "A":
        return (props.ARecords ?? []).length;
      case "AAAA":
        return (props.AAAARecords ?? []).length;
      case "CNAME":
        return props.CNAMERecord ? 1 : 0;
      case "MX":
        return (props.MXRecords ?? []).length;
      case "NS":
        return (props.NSRecords ?? []).length;
      case "TXT":
        return (props.TXTRecords ?? []).length;
      case "PTR":
        return (props.PTRRecords ?? []).length;
      default:
        return 0;
    }
  }

  async function addRecord(zoneId: string, record: DnsRecordInput): Promise<DnsRecord> {
    const { resourceGroup, zoneName } = decodeZoneId(zoneId);

    let relName = record.name;
    if (relName.endsWith(`.${zoneName}`)) relName = relName.slice(0, -(zoneName.length + 1));
    if (relName === zoneName) relName = "@";

    const path = `/subscriptions/${config.subscriptionId}/resourceGroups/${resourceGroup}/providers/Microsoft.Network/dnsZones/${zoneName}/${record.type}/${relName}`;

    let existing: any = null;
    try {
      existing = await armFetch(path);
    } catch {
      // 404 means it doesn't exist yet
    }

    const props = existing?.properties ?? { TTL: Number(record.ttl) || 3600 };
    props.TTL = Number(record.ttl) || props.TTL || 3600;
    appendToRecordSet(props, record.type, record.content, record.priority);

    await armFetch(path, { method: "PUT", body: JSON.stringify({ properties: props }) });

    return {
      id: `${relName}::${record.type}::${record.content}`,
      type: record.type,
      name: relName === "@" ? zoneName : `${relName}.${zoneName}`,
      content: record.content,
      ttl: props.TTL,
      priority: record.priority ?? null,
    };
  }

  async function updateRecord(zoneId: string, recordId: string, record: DnsRecordInput): Promise<DnsRecord> {
    const { resourceGroup, zoneName } = decodeZoneId(zoneId);
    const parts = recordId.split("::");
    const oldRelName = parts[0];
    const type = parts[1];
    const oldContent = parts.slice(2).join("::");

    let newRelName = record.name;
    if (newRelName.endsWith(`.${zoneName}`)) newRelName = newRelName.slice(0, -(zoneName.length + 1));
    if (newRelName === zoneName) newRelName = "@";

    const oldPath = `/subscriptions/${config.subscriptionId}/resourceGroups/${resourceGroup}/providers/Microsoft.Network/dnsZones/${zoneName}/${type}/${oldRelName}`;
    const newPath = `/subscriptions/${config.subscriptionId}/resourceGroups/${resourceGroup}/providers/Microsoft.Network/dnsZones/${zoneName}/${type}/${newRelName}`;

    let existing: any = null;
    try {
      existing = await armFetch(oldPath);
    } catch {
      // doesn't exist in Azure
    }

    if (existing) {
      const props = existing.properties;
      removeFromRecordSet(props, type, oldContent);
      props.TTL = Number(record.ttl) || props.TTL || 3600;
      appendToRecordSet(props, type, record.content, record.priority);

      if (oldRelName === newRelName) {
        await armFetch(oldPath, { method: "PUT", body: JSON.stringify({ properties: props }) });
      } else {
        await armFetch(oldPath, { method: "DELETE" });
        const newProps: any = { TTL: props.TTL };
        appendToRecordSet(newProps, type, record.content, record.priority);
        await armFetch(newPath, { method: "PUT", body: JSON.stringify({ properties: newProps }) });
      }
    } else {
      await addRecord(zoneId, record);
    }

    return {
      id: `${newRelName}::${type}::${record.content}`,
      type,
      name: newRelName === "@" ? zoneName : `${newRelName}.${zoneName}`,
      content: record.content,
      ttl: Number(record.ttl) || 3600,
      priority: record.priority ?? null,
    };
  }

  async function deleteRecord(zoneId: string, recordId: string): Promise<void> {
    const { resourceGroup, zoneName } = decodeZoneId(zoneId);
    const parts = recordId.split("::");
    const relName = parts[0];
    const type = parts[1];
    const content = parts.slice(2).join("::");

    const path = `/subscriptions/${config.subscriptionId}/resourceGroups/${resourceGroup}/providers/Microsoft.Network/dnsZones/${zoneName}/${type}/${relName}`;
    const existing = await armFetch(path);
    const props = existing.properties;

    removeFromRecordSet(props, type, content);

    const remaining = countRecords(props, type);
    if (remaining === 0) {
      await armFetch(path, { method: "DELETE" });
    } else {
      await armFetch(path, { method: "PUT", body: JSON.stringify({ properties: props }) });
    }
  }

  return withDiagLogging("azure", { listZones, listRecords, addRecord, updateRecord, deleteRecord });
}