import { constants, realpathSync, statSync, accessSync } from "node:fs";
import { isAbsolute, relative } from "node:path";
import { buildInstallationContract, type InstallationSuffix } from "./contracts.js";
import {
  DWH_TRANSPORTS,
  validateWorkspaceDescriptor,
  type DwhTransport,
  type WorkspaceDescriptor,
} from "./schema.js";

export interface ResolvedEvidenceBinding {
  values: Record<string, string>;
  missing: string[];
}

export interface RuntimeBindings {
  dwh: ResolvedBinding;
  evidence: ResolvedEvidenceBinding;
}

export interface ResolvedBinding {
  transport: DwhTransport;
  values: Record<string, string>;
  missing: string[];
}

const REQUIRED_SUFFIXES: Record<DwhTransport, readonly InstallationSuffix[]> = {
  postgres_direct: ["HOST", "PORT", "USER", "PASSWORD_FILE"],
  rest_api: ["BASE_URL", "API_KEY_FILE"],
  ssh_tunnel: [
    "USER", "PASSWORD_FILE", "SSH_HOST", "SSH_PORT", "SSH_USER",
    "SSH_PRIVATE_KEY_FILE", "SSH_KNOWN_HOSTS_FILE", "SSH_TARGET_HOST", "SSH_TARGET_PORT",
  ],
};

function isTransport(value: string | undefined): value is DwhTransport {
  return value !== undefined && (DWH_TRANSPORTS as readonly string[]).includes(value);
}

function isInside(path: string, root: string): boolean {
  const pathRelative = relative(root, path);
  return pathRelative !== "" && !pathRelative.startsWith("..") && !isAbsolute(pathRelative);
}

function safeSecretFilePath(path: string, secretRoots: readonly string[]): string | undefined {
  if (!isAbsolute(path)) return undefined;

  try {
    const resolvedPath = realpathSync(path);
    const resolvedRoots = secretRoots.map((root) => realpathSync(root));
    if (!resolvedRoots.some((root) => isInside(resolvedPath, root))) return undefined;
    if (!statSync(resolvedPath).isFile()) return undefined;
    accessSync(resolvedPath, constants.R_OK);
    return resolvedPath;
  } catch {
    return undefined;
  }
}

function requireSupportedDescriptor(workspace: unknown): void {
  if (typeof workspace !== "object" || workspace === null) {
    throw new Error("Workspace bindings support only workspace schema version 3");
  }
  const metadata = Reflect.get(workspace, "workspace");
  if (typeof metadata !== "object" || metadata === null
    || Reflect.get(metadata, "schema_version") !== 3) {
    throw new Error("Workspace bindings support only workspace schema version 3");
  }
}

function requiredSuffixes(
  workspace: WorkspaceDescriptor,
  transport: DwhTransport,
): readonly InstallationSuffix[] {
  const required = REQUIRED_SUFFIXES[transport];
  return transport === "rest_api" && workspace.diagnostics?.dwh_rest?.auth === "none"
    ? required.filter((suffix) => suffix !== "API_KEY_FILE")
    : required;
}

/**
 * Resolve only installation-local values. Secret files remain file paths: their contents are
 * deliberately left for the harness secret-file loader, so bindings cannot leak credentials.
 */
export function resolveBinding(
  workspace: WorkspaceDescriptor,
  role: "DWH",
  env: NodeJS.ProcessEnv,
  secretRoots: readonly string[],
): ResolvedBinding {
  requireSupportedDescriptor(workspace);
  const descriptor = validateWorkspaceDescriptor(workspace);
  const contract = buildInstallationContract(descriptor);
  const variables = contract.variables.filter((variable) => variable.role === role);
  const transportVariable = variables.find((variable) => variable.suffix === "TRANSPORT");
  const supported = descriptor.dwh.supported_transports;
  const selectedValue = transportVariable ? env[transportVariable.name] : undefined;
  const selectedTransport = isTransport(selectedValue) ? selectedValue : supported[0];
  const missing: string[] = [];

  if (transportVariable && (!isTransport(selectedValue) || !supported.includes(selectedTransport))) {
    missing.push(transportVariable.name);
  }

  const required = new Set(requiredSuffixes(descriptor, selectedTransport));
  const values: Record<string, string> = {};
  for (const variable of variables) {
    if (variable.suffix === "TRANSPORT") continue;
    if (variable.transports && !variable.transports.includes(selectedTransport)) continue;

    const value = env[variable.name];
    const present = value !== undefined && value.trim() !== "";
    const safePath = variable.secret && present ? safeSecretFilePath(value, secretRoots) : undefined;
    const safe = !variable.secret || safePath !== undefined;
    if ((required.has(variable.suffix) && !present) || (present && !safe)) {
      missing.push(variable.name);
    }
    if (present && safe) values[variable.name] = variable.secret ? safePath! : value;
  }

  return { transport: selectedTransport, values, missing };
}

/** Resolve descriptor-selected Evidence credentials without reading any secret file contents. */
export function resolveEvidenceBinding(
  workspace: WorkspaceDescriptor,
  env: NodeJS.ProcessEnv,
  secretRoots: readonly string[],
): ResolvedEvidenceBinding {
  requireSupportedDescriptor(workspace);
  const descriptor = validateWorkspaceDescriptor(workspace);
  const variables = buildInstallationContract(descriptor).variables
    .filter((variable) => variable.role === "EVIDENCE");
  if (variables.length === 0) return { values: {}, missing: [] };

  const source = descriptor.evidence?.source;
  const required = new Set<InstallationSuffix>(
    source?.type === "http"
      ? ["SIGNED_URLS_FILE"]
      : source?.type === "s3"
        ? ["ACCESS_KEY_FILE", "SECRET_KEY_FILE"]
        : [],
  );
  const values: Record<string, string> = {};
  const missing: string[] = [];
  for (const variable of variables) {
    const value = env[variable.name];
    const present = value !== undefined && value.trim() !== "";
    const safePath = present ? safeSecretFilePath(value, secretRoots) : undefined;
    if ((required.has(variable.suffix) && !present) || (present && safePath === undefined)) {
      missing.push(variable.name);
    }
    if (safePath !== undefined) values[variable.name] = safePath;
  }
  return { values, missing };
}

/** Resolve the complete schema-v3 runtime binding set. */
export function resolveRuntimeBindings(
  workspace: WorkspaceDescriptor,
  env: NodeJS.ProcessEnv,
  secretRoots: readonly string[],
): RuntimeBindings {
  requireSupportedDescriptor(workspace);
  const descriptor = validateWorkspaceDescriptor(workspace);

  return {
    dwh: resolveBinding(descriptor, "DWH", env, secretRoots),
    evidence: resolveEvidenceBinding(descriptor, env, secretRoots),
  };
}

/** SSH bindings remain diagnostic-only until the session runtime owns a long-lived tunnel. */
export function supportsSessionRuntime(bindings: RuntimeBindings): boolean {
  return bindings.dwh.transport !== "ssh_tunnel" && bindings.evidence.missing.length === 0;
}