import path from "node:path";
import { isVersionCompatible, moduleIdSchema, semanticVersionSchema } from "@ekklesia/contracts";
import { getTableName } from "drizzle-orm";
import {
  type CreateIdentityConfigOptions,
  createIdentityConfig,
  IdentityConfigError,
} from "../identity/config.js";
import { identityAdapterSchema } from "../identity/schema.js";
import {
  createPostgresMigrationDatabase,
  discoverAllMigrations,
  type MigrationDatabase,
  type MigrationPlanResult,
  MigrationRunnerError,
  PostgresMigrationDatabaseError,
  type PostgresMigrationDatabaseOptions,
  planModuleMigrations,
} from "../migrations/index.js";
import {
  type DiscoveredModule,
  discoverModuleSchemas,
  discoverModules,
  type ModuleDiscoveryOptions,
  type ModuleMigrationAggregate,
  type ModuleSchemaAggregate,
} from "../modules/index.js";

export type DoctorCheckId =
  | "platform.runtime"
  | "modules.discovery"
  | "modules.dependencies"
  | "schemas.discovery"
  | "migrations.discovery"
  | "postgresql.connection"
  | "postgresql.plan"
  | "identity.configuration"
  | "object-storage.integration";

export type DoctorCheckStatus = "failure" | "pass" | "skipped" | "warning";
export type DoctorResult = "not-ready" | "ready" | "ready-with-warnings";

export interface DoctorCheck {
  readonly details: readonly string[];
  readonly id: DoctorCheckId;
  readonly status: DoctorCheckStatus;
  readonly summary: string;
}

export interface DoctorReport {
  readonly checks: readonly DoctorCheck[];
  readonly result: DoctorResult;
}

export interface DoctorIdentityConfigurationOptions {
  readonly baseUrl?: string | undefined;
  readonly environment?: CreateIdentityConfigOptions["environment"];
  readonly secret?: string | undefined;
  readonly trustedOrigins?: readonly string[] | undefined;
}

export interface DoctorOptions {
  readonly databaseUrl?: string | undefined;
  readonly identityConfiguration?: DoctorIdentityConfigurationOptions | undefined;
  readonly moduleDiscovery: ModuleDiscoveryOptions;
  readonly runtimeRange: string;
  readonly runtimeVersion: string;
}

export interface DoctorDependencies {
  readonly createMigrationDatabase: (
    connectionString: string,
    options: PostgresMigrationDatabaseOptions,
  ) => MigrationDatabase;
  readonly discoverMigrations: (
    options: ModuleDiscoveryOptions,
  ) => Promise<ModuleMigrationAggregate>;
  readonly discoverModules: (
    options: ModuleDiscoveryOptions,
  ) => Promise<readonly DiscoveredModule[]>;
  readonly discoverSchemas: (options: ModuleDiscoveryOptions) => Promise<ModuleSchemaAggregate>;
  readonly planMigrations: (options: {
    readonly aggregate: ModuleMigrationAggregate;
    readonly database: MigrationDatabase;
  }) => Promise<MigrationPlanResult>;
  readonly runtimeSatisfies: (version: string, range: string) => boolean;
}

const doctorPostgresTimeoutMs = 10_000;
const checksumPattern = /^[a-f0-9]{64}$/u;
const migrationIdentityPattern =
  /^[a-z][a-z0-9]*(?:-[a-z0-9]+)*:\d{4,}_[a-z][a-z0-9]*(?:_[a-z0-9]+)*$/u;

async function discoverAllMigrationsForRuntime(
  options: ModuleDiscoveryOptions,
): Promise<ModuleMigrationAggregate> {
  return discoverAllMigrations({
    coreMigrationsDirectory: path.join(path.dirname(options.modulesDirectory), "core", "drizzle"),
    moduleDiscovery: options,
  });
}

const productionDependencies: DoctorDependencies = Object.freeze({
  createMigrationDatabase: createPostgresMigrationDatabase,
  discoverMigrations: discoverAllMigrationsForRuntime,
  discoverModules,
  discoverSchemas: discoverModuleSchemas,
  planMigrations: planModuleMigrations,
  runtimeSatisfies: isVersionCompatible,
});

function plural(count: number, singular: string): string {
  return count === 1 ? singular : `${singular}s`;
}

function freezeCheck(
  id: DoctorCheckId,
  status: DoctorCheckStatus,
  summary: string,
  details: readonly string[] = [],
): DoctorCheck {
  return Object.freeze({
    details: Object.freeze([...details]),
    id,
    status,
    summary,
  });
}

export function deriveDoctorResult(checks: readonly DoctorCheck[]): DoctorResult {
  if (checks.some((check) => check.status === "failure")) {
    return "not-ready";
  }
  if (checks.some((check) => check.status === "warning" || check.status === "skipped")) {
    return "ready-with-warnings";
  }
  return "ready";
}

function publishReport(checks: readonly DoctorCheck[]): DoctorReport {
  const frozenChecks = Object.freeze([...checks]);
  return Object.freeze({ checks: frozenChecks, result: deriveDoctorResult(frozenChecks) });
}

function safeModuleDetails(modules: readonly DiscoveredModule[]): readonly string[] {
  return modules.map((module) => {
    const id = module.manifest.id;
    const version = module.manifest.version;
    if (
      !moduleIdSchema.safeParse(id).success ||
      !semanticVersionSchema.safeParse(version).success
    ) {
      throw new TypeError("Unsafe module diagnostic value.");
    }
    return `${id} ${version}`;
  });
}

function safeMigrationReference(identity: string, checksum: string): string {
  if (!migrationIdentityPattern.test(identity) || !checksumPattern.test(checksum)) {
    throw new TypeError("Unsafe migration diagnostic value.");
  }
  return `${identity} · ${checksum.slice(0, 12)}`;
}

function moduleDiscoveryFailure(error: unknown): DoctorCheck {
  const details =
    error instanceof Error && error.name === "ModuleDiscoveryError"
      ? ["The installed module inventory is invalid."]
      : ["Static module discovery could not be completed."];
  return freezeCheck("modules.discovery", "failure", "Module discovery failed", details);
}

function schemaDiscoveryFailure(): DoctorCheck {
  return freezeCheck("schemas.discovery", "failure", "Schema validation failed", [
    "Installed module schemas could not be validated.",
  ]);
}

function migrationDiscoveryFailure(): DoctorCheck {
  return freezeCheck("migrations.discovery", "failure", "Migration validation failed", [
    "Installed module migrations could not be validated.",
  ]);
}

function configuredDatabaseFailure(error: unknown): readonly [DoctorCheck, DoctorCheck] {
  if (error instanceof MigrationRunnerError) {
    if (error.code === "MIGRATION_CONNECTION_FAILED") {
      return [
        freezeCheck("postgresql.connection", "failure", "Connection failed", [
          "The configured PostgreSQL database could not be reached.",
        ]),
        freezeCheck("postgresql.plan", "skipped", "Migration plan skipped", [
          "A successful PostgreSQL connection is required.",
        ]),
      ];
    }

    return [
      freezeCheck("postgresql.connection", "pass", "Connection established"),
      freezeCheck("postgresql.plan", "failure", "Migration history validation failed", [
        migrationPlanFailureDetail(error.code),
      ]),
    ];
  }

  if (error instanceof PostgresMigrationDatabaseError) {
    return [
      freezeCheck("postgresql.connection", "failure", "PostgreSQL configuration invalid", [
        "The configured database connection could not be prepared safely.",
      ]),
      freezeCheck("postgresql.plan", "skipped", "Migration plan skipped", [
        "A valid PostgreSQL configuration is required.",
      ]),
    ];
  }

  return [
    freezeCheck("postgresql.connection", "failure", "PostgreSQL diagnostic failed", [
      "The configured database could not be inspected safely.",
    ]),
    freezeCheck("postgresql.plan", "skipped", "Migration plan skipped", [
      "PostgreSQL connectivity could not be confirmed.",
    ]),
  ];
}

function migrationPlanFailureDetail(code: MigrationRunnerError["code"]): string {
  switch (code) {
    case "MIGRATION_CHECKSUM_MISMATCH":
      return "An applied migration checksum disagrees with packaged inventory.";
    case "MIGRATION_HISTORY_INVALID":
      return "Applied migration history is invalid.";
    case "MIGRATION_HISTORY_READ_FAILED":
      return "Applied migration history could not be read safely.";
    case "MIGRATION_UNKNOWN_APPLIED":
      return "Applied migration history contains an unknown identity.";
    case "MIGRATION_CLEANUP_FAILED":
      return "The read-only PostgreSQL session did not close cleanly.";
    default:
      return "The read-only migration plan could not be completed safely.";
  }
}

function migrationPlanCheck(plan: MigrationPlanResult): DoctorCheck {
  const pendingCount = plan.entries.filter((entry) => entry.status === "pending").length;
  const blockedCount = plan.entries.filter((entry) => entry.status === "approval-blocked").length;
  const appliedCount = plan.entries.filter((entry) => entry.status === "applied").length;

  if (
    appliedCount !== plan.appliedCount ||
    pendingCount + blockedCount !== plan.pendingCount ||
    blockedCount !== plan.approvalRequiredCount
  ) {
    throw new TypeError("Inconsistent migration plan diagnostic value.");
  }

  const details = [
    `${appliedCount} applied · ${pendingCount} pending · ${blockedCount} approval-blocked`,
    ...plan.entries.map((entry) => {
      if (!(["applied", "approval-blocked", "pending"] as const).includes(entry.status)) {
        throw new TypeError("Unsafe migration plan diagnostic value.");
      }
      return `${entry.status} · ${safeMigrationReference(entry.identity, entry.checksum)}`;
    }),
  ];

  if (pendingCount + blockedCount === 0) {
    return freezeCheck("postgresql.plan", "pass", "Migration history current", details);
  }

  const attentionCount = pendingCount + blockedCount;
  return freezeCheck(
    "postgresql.plan",
    "warning",
    attentionCount === 1
      ? "1 migration requires attention"
      : `${attentionCount} migrations require attention`,
    details,
  );
}

function identitySchemaSummary(): string {
  const tableNames = Object.values(identityAdapterSchema)
    .map((table) => getTableName(table))
    .sort();
  return `Core identity schema defines ${tableNames.length} ${plural(tableNames.length, "table")} (${tableNames.join(", ")}).`;
}

/**
 * Pure configuration validation only: never constructs Better Auth, never opens a database
 * connection, and never prints the configured secret, base URL, or trusted origins. Missing
 * configuration is a skip, not a failure — Doctor does not require identity to be configured yet.
 */
function identityConfigurationCheck(
  input: DoctorIdentityConfigurationOptions | undefined,
): DoctorCheck {
  const schemaDetail = identitySchemaSummary();
  const hasAnyValue =
    input?.secret !== undefined ||
    input?.baseUrl !== undefined ||
    (input?.trustedOrigins?.length ?? 0) > 0;

  if (!hasAnyValue) {
    return freezeCheck("identity.configuration", "skipped", "Identity configuration skipped", [
      schemaDetail,
      "Identity runtime configuration (signing key, base URL, trusted origins) is not set.",
    ]);
  }

  try {
    createIdentityConfig(
      {
        baseUrl: input?.baseUrl,
        secret: input?.secret,
        trustedOrigins: input?.trustedOrigins,
      },
      { environment: input?.environment ?? "production" },
    );
    return freezeCheck("identity.configuration", "pass", "Identity configuration valid", [
      schemaDetail,
    ]);
  } catch (error) {
    const code =
      error instanceof IdentityConfigError ? error.code : "IDENTITY_CONFIGURATION_INVALID";
    return freezeCheck("identity.configuration", "failure", "Identity configuration invalid", [
      schemaDetail,
      `[${code}] Configured identity values failed validation.`,
    ]);
  }
}

function skippedPostgresChecks(detail: string): readonly [DoctorCheck, DoctorCheck] {
  return [
    freezeCheck("postgresql.connection", "skipped", "Connection check skipped", [detail]),
    freezeCheck("postgresql.plan", "skipped", "Migration plan skipped", [
      "A validated migration inventory and configured PostgreSQL connection are required.",
    ]),
  ];
}

export function doctorExitCode(report: DoctorReport): 0 | 1 {
  return report.result === "not-ready" ? 1 : 0;
}

export async function diagnoseEkklesia(
  options: DoctorOptions,
  dependencies: DoctorDependencies = productionDependencies,
): Promise<DoctorReport> {
  let runtimeCheck: DoctorCheck;
  try {
    runtimeCheck = dependencies.runtimeSatisfies(options.runtimeVersion, options.runtimeRange)
      ? freezeCheck("platform.runtime", "pass", "Runtime version supported", [
          "Active Node.js satisfies the declared supported range.",
        ])
      : freezeCheck("platform.runtime", "failure", "Runtime version unsupported", [
          "Install a Node.js version supported by this repository.",
        ]);
  } catch {
    runtimeCheck = freezeCheck("platform.runtime", "failure", "Runtime validation failed", [
      "The active Node.js runtime could not be validated safely.",
    ]);
  }

  let discoveredModules: readonly DiscoveredModule[] | undefined;
  let moduleCheck: DoctorCheck;
  let dependencyCheck: DoctorCheck;
  try {
    discoveredModules = await dependencies.discoverModules(options.moduleDiscovery);
    const moduleDetails = safeModuleDetails(discoveredModules);
    moduleCheck = freezeCheck(
      "modules.discovery",
      "pass",
      "Module discovery complete",
      discoveredModules.length === 0 ? ["0 modules installed"] : moduleDetails,
    );
    dependencyCheck = freezeCheck("modules.dependencies", "pass", "Dependency graph valid", [
      discoveredModules.length === 0
        ? "Dependency order is empty."
        : `Order: ${discoveredModules.map((module) => module.manifest.id).join(" → ")}`,
    ]);
  } catch (error) {
    moduleCheck = moduleDiscoveryFailure(error);
    dependencyCheck = freezeCheck("modules.dependencies", "skipped", "Dependency check skipped", [
      "Complete module discovery is required.",
    ]);
  }

  let schemaCheck: DoctorCheck;
  let migrationCheck: DoctorCheck;
  let migrations: ModuleMigrationAggregate | undefined;

  if (!discoveredModules) {
    schemaCheck = freezeCheck("schemas.discovery", "skipped", "Schema validation skipped", [
      "Complete module discovery is required.",
    ]);
    migrationCheck = freezeCheck(
      "migrations.discovery",
      "skipped",
      "Migration validation skipped",
      ["Complete module discovery is required."],
    );
  } else {
    try {
      const schemas = await dependencies.discoverSchemas(options.moduleDiscovery);
      schemaCheck = freezeCheck("schemas.discovery", "pass", "Schemas validated", [
        `${schemas.discoveredModules.length} ${plural(schemas.discoveredModules.length, "module")} · ${schemas.tables.length} ${plural(schemas.tables.length, "table")}`,
      ]);
    } catch {
      schemaCheck = schemaDiscoveryFailure();
    }

    try {
      migrations = await dependencies.discoverMigrations(options.moduleDiscovery);
      const inventory = migrations.migrations.map((migration) =>
        safeMigrationReference(migration.identity, migration.checksum),
      );
      migrationCheck = freezeCheck("migrations.discovery", "pass", "Migrations validated", [
        `${migrations.migrations.length} ${plural(migrations.migrations.length, "migration")} · checksums valid`,
        ...inventory,
      ]);
    } catch {
      migrations = undefined;
      migrationCheck = migrationDiscoveryFailure();
    }
  }

  let postgresConnectionCheck: DoctorCheck;
  let postgresPlanCheck: DoctorCheck;
  const databaseUrl = options.databaseUrl;
  const databaseConfigured = typeof databaseUrl === "string" && databaseUrl.trim() !== "";

  if (!migrations) {
    [postgresConnectionCheck, postgresPlanCheck] = skippedPostgresChecks(
      "Complete migration discovery is required.",
    );
  } else if (!databaseConfigured) {
    [postgresConnectionCheck, postgresPlanCheck] = skippedPostgresChecks(
      "DATABASE_URL is not configured.",
    );
  } else {
    try {
      const database = dependencies.createMigrationDatabase(databaseUrl, {
        connectionTimeoutMs: doctorPostgresTimeoutMs,
        operationTimeoutMs: doctorPostgresTimeoutMs,
      });
      const plan = await dependencies.planMigrations({ aggregate: migrations, database });
      postgresConnectionCheck = freezeCheck(
        "postgresql.connection",
        "pass",
        "Connection established",
      );
      postgresPlanCheck = migrationPlanCheck(plan);
    } catch (error) {
      [postgresConnectionCheck, postgresPlanCheck] = configuredDatabaseFailure(error);
    }
  }

  const identityCheck = identityConfigurationCheck(options.identityConfiguration);

  const storageCheck = freezeCheck("object-storage.integration", "skipped", "Check unavailable", [
    "Core storage integration has not been implemented yet.",
  ]);

  return publishReport([
    runtimeCheck,
    moduleCheck,
    dependencyCheck,
    schemaCheck,
    migrationCheck,
    postgresConnectionCheck,
    postgresPlanCheck,
    identityCheck,
    storageCheck,
  ]);
}