import { promises as fs } from "node:fs";
import path from "node:path";
import type { AdapterSkillEntry, AdapterSkillSnapshot } from "./types.js";
import type { AgentCompanySkillEntry, InstalledSkillTarget } from "./server-utils-skills.js";

interface PersistentSkillSnapshotOptions {
  adapterType: string;
  availableEntries: AgentCompanySkillEntry[];
  desiredSkills: string[];
  installed: Map<string, InstalledSkillTarget>;
  skillsHome: string;
  locationLabel?: string | null;
  installedDetail?: string | null;
  missingDetail: string;
  externalConflictDetail: string;
  externalDetail: string;
  warnings?: string[];
}

function normalizePathSlashes(value: string): string {
  return value.replaceAll("\\", "/");
}

function isMaintainerOnlySkillTarget(candidate: string): boolean {
  return normalizePathSlashes(candidate).includes("/.agents/skills/");
}

function skillLocationLabel(value: string | null | undefined): string | null {
  if (typeof value !== "string") return null;
  const trimmed = value.trim();
  return trimmed.length > 0 ? trimmed : null;
}

function buildManagedSkillOrigin(entry: { required?: boolean }): Pick<
  AdapterSkillEntry,
  "origin" | "originLabel" | "readOnly"
> {
  if (entry.required) {
    return {
      origin: "paperclip_required",
      originLabel: "Required by AgentCompany",
      readOnly: false,
    };
  }
  return {
    origin: "company_managed",
    originLabel: "Managed by AgentCompany",
    readOnly: false,
  };
}

function canonicalizeDesiredAgentCompanySkillReference(
  reference: string,
  availableEntries: Array<{ key: string; runtimeName?: string | null }>,
): string {
  const normalizedReference = reference.trim().toLowerCase();
  if (!normalizedReference) return "";

  const exactKey = availableEntries.find((entry) => entry.key.trim().toLowerCase() === normalizedReference);
  if (exactKey) return exactKey.key;

  const byRuntimeName = availableEntries.filter((entry) =>
    typeof entry.runtimeName === "string" && entry.runtimeName.trim().toLowerCase() === normalizedReference,
  );
  if (byRuntimeName.length === 1) return byRuntimeName[0]!.key;

  const slugMatches = availableEntries.filter((entry) =>
    entry.key.trim().toLowerCase().split("/").pop() === normalizedReference,
  );
  if (slugMatches.length === 1) return slugMatches[0]!.key;

  return normalizedReference;
}

/**
 * Build an AdapterSkillSnapshot for persistent-mode adapters (Gemini, Codex).
 * Compares available entries against installed state and desired skill list.
 */
export function buildPersistentSkillSnapshot(
  options: PersistentSkillSnapshotOptions,
): AdapterSkillSnapshot {
  const {
    adapterType,
    availableEntries,
    desiredSkills,
    installed,
    skillsHome,
    locationLabel,
    installedDetail,
    missingDetail,
    externalConflictDetail,
    externalDetail,
  } = options;
  const availableByKey = new Map(availableEntries.map((entry) => [entry.key, entry]));
  const desiredSet = new Set(desiredSkills);
  const entries: AdapterSkillEntry[] = [];
  const warnings = [...(options.warnings ?? [])];

  for (const available of availableEntries) {
    const installedEntry = installed.get(available.runtimeName) ?? null;
    const desired = desiredSet.has(available.key);
    let state: AdapterSkillEntry["state"] = "available";
    let managed = false;
    let detail: string | null = null;

    if (installedEntry?.targetPath === available.source) {
      managed = true;
      state = desired ? "installed" : "stale";
      detail = installedDetail ?? null;
    } else if (installedEntry) {
      state = "external";
      detail = desired ? externalConflictDetail : externalDetail;
    } else if (desired) {
      state = "missing";
      detail = missingDetail;
    }

    entries.push({
      key: available.key,
      runtimeName: available.runtimeName,
      desired,
      managed,
      state,
      sourcePath: available.source,
      targetPath: path.join(skillsHome, available.runtimeName),
      detail,
      required: Boolean(available.required),
      requiredReason: available.requiredReason ?? null,
      ...buildManagedSkillOrigin(available),
    });
  }

  for (const desiredSkill of desiredSkills) {
    if (availableByKey.has(desiredSkill)) continue;
    warnings.push(`Desired skill "${desiredSkill}" is not available from the AgentCompany skills directory.`);
    entries.push({
      key: desiredSkill,
      runtimeName: null,
      desired: true,
      managed: true,
      state: "missing",
      sourcePath: null,
      targetPath: null,
      detail: "AgentCompany cannot find this skill in the local runtime skills directory.",
      origin: "external_unknown",
      originLabel: "External or unavailable",
      readOnly: false,
    });
  }

  for (const [name, installedEntry] of installed.entries()) {
    if (availableEntries.some((entry) => entry.runtimeName === name)) continue;
    entries.push({
      key: name,
      runtimeName: name,
      desired: false,
      managed: false,
      state: "external",
      origin: "user_installed",
      originLabel: "User-installed",
      locationLabel: skillLocationLabel(locationLabel),
      readOnly: true,
      sourcePath: null,
      targetPath: installedEntry.targetPath ?? path.join(skillsHome, name),
      detail: externalDetail,
    });
  }

  entries.sort((left, right) => left.key.localeCompare(right.key));

  return {
    adapterType,
    supported: true,
    mode: "persistent",
    desiredSkills,
    entries,
    warnings,
  };
}

/**
 * Read the desired skill sync preference from adapter config.
 */
export function readAgentCompanySkillSyncPreference(config: Record<string, unknown>): {
  explicit: boolean;
  desiredSkills: string[];
} {
  const raw = config.agentCompanySkillSync;
  if (typeof raw !== "object" || raw === null || Array.isArray(raw)) {
    return { explicit: false, desiredSkills: [] };
  }
  const syncConfig = raw as Record<string, unknown>;
  const desiredValues = syncConfig.desiredSkills;
  const desired = Array.isArray(desiredValues)
    ? desiredValues
        .filter((value): value is string => typeof value === "string")
        .map((value) => value.trim())
        .filter(Boolean)
    : [];
  return {
    explicit: Object.prototype.hasOwnProperty.call(raw, "desiredSkills"),
    desiredSkills: Array.from(new Set(desired)),
  };
}

/**
 * Resolve the canonical desired skill list from config and available entries.
 * Required skills are always included; explicit preferences are canonicalized.
 */
export function resolveAgentCompanyDesiredSkillNames(
  config: Record<string, unknown>,
  availableEntries: Array<{ key: string; runtimeName?: string | null; required?: boolean }>,
): string[] {
  const preference = readAgentCompanySkillSyncPreference(config);
  const requiredSkills = availableEntries
    .filter((entry) => entry.required)
    .map((entry) => entry.key);
  if (!preference.explicit) {
    return Array.from(new Set(requiredSkills));
  }
  const desiredSkills = preference.desiredSkills
    .map((reference) => canonicalizeDesiredAgentCompanySkillReference(reference, availableEntries))
    .filter(Boolean);
  return Array.from(new Set([...requiredSkills, ...desiredSkills]));
}

/**
 * Create or repair a symlink from source to target skill directory.
 * Returns the action taken: "created", "repaired", or "skipped".
 */
export async function ensureAgentCompanySkillSymlink(
  source: string,
  target: string,
  linkSkill: (source: string, target: string) => Promise<void> = (linkSource, linkTarget) =>
    fs.symlink(linkSource, linkTarget),
): Promise<"created" | "repaired" | "skipped"> {
  const existing = await fs.lstat(target).catch(() => null);
  if (!existing) {
    await linkSkill(source, target);
    return "created";
  }

  if (!existing.isSymbolicLink()) {
    return "skipped";
  }

  const linkedPath = await fs.readlink(target).catch(() => null);
  if (!linkedPath) return "skipped";

  const resolvedLinkedPath = path.resolve(path.dirname(target), linkedPath);
  if (resolvedLinkedPath === source) {
    return "skipped";
  }

  const linkedPathExists = await fs.stat(resolvedLinkedPath).then(() => true).catch(() => false);
  if (linkedPathExists) {
    return "skipped";
  }

  await fs.unlink(target);
  await linkSkill(source, target);
  return "repaired";
}

/**
 * Remove symlinks in skillsHome that point to maintainer-only paths
 * (.agents/skills/) and are not in the allowed set.
 */
export async function removeMaintainerOnlySkillSymlinks(
  skillsHome: string,
  allowedSkillNames: Iterable<string>,
): Promise<string[]> {
  const allowed = new Set(Array.from(allowedSkillNames));
  try {
    const entries = await fs.readdir(skillsHome, { withFileTypes: true });
    const removed: string[] = [];
    for (const entry of entries) {
      if (allowed.has(entry.name)) continue;

      const target = path.join(skillsHome, entry.name);
      const existing = await fs.lstat(target).catch(() => null);
      if (!existing?.isSymbolicLink()) continue;

      const linkedPath = await fs.readlink(target).catch(() => null);
      if (!linkedPath) continue;

      const resolvedLinkedPath = path.isAbsolute(linkedPath)
        ? linkedPath
        : path.resolve(path.dirname(target), linkedPath);
      if (
        !isMaintainerOnlySkillTarget(linkedPath) &&
        !isMaintainerOnlySkillTarget(resolvedLinkedPath)
      ) {
        continue;
      }

      await fs.unlink(target);
      removed.push(entry.name);
    }

    return removed;
  } catch {
    return [];
  }
}