import { Prisma } from '@vector/db';
import type {
  CreatePartRequest,
  PaginationQuery,
  PartListQuery,
  PartState as PartStateValue,
  UpdatePartRequest,
} from '@vector/shared';
import { errors } from '../lib/http-error.js';
import * as partModelsSvc from './part-models.js';
import * as tagsSvc from './tags.js';
import type { Actor, Tx } from './types.js';

// Enforces the Part state/location invariant and auto-clears stale fields on state transitions.
// The matrix is:
//   DEPLOYED                          — hostId required, binId forbidden, custodianId forbidden
//   SPARE / BROKEN / PENDING_DESTRUCTION — binId optional, hostId + custodian forbidden
//   PENDING_DROP_IN_CUSTODY / PENDING_DESTRUCTION_IN_CUSTODY
//                                     — custodianId required, host + bin forbidden
// Callers only need to pass what's changing; anything omitted is inherited from `current`.
function resolveLocation(
  state: PartStateValue,
  input: {
    binId?: string | null;
    hostId?: string | null;
    custodianId?: string | null;
  },
  current: {
    binId: string | null;
    hostId: string | null;
    custodianId: string | null;
  } = { binId: null, hostId: null, custodianId: null },
): { binId: string | null; hostId: string | null; custodianId: string | null } {
  if (state === 'DEPLOYED') {
    const hostId = input.hostId !== undefined ? input.hostId : current.hostId;
    if (!hostId) throw errors.badRequest('A deployed part must be assigned to a host');
    if (input.binId) {
      throw errors.badRequest('A deployed part cannot also be in a storage bin');
    }
    if (input.custodianId) {
      throw errors.badRequest('A deployed part cannot be in custody');
    }
    return { binId: null, hostId, custodianId: null };
  }

  if (state === 'PENDING_DROP_IN_CUSTODY' || state === 'PENDING_DESTRUCTION_IN_CUSTODY') {
    const custodianId =
      input.custodianId !== undefined ? input.custodianId : current.custodianId;
    if (!custodianId) throw errors.badRequest('A part in custody must name a custodian');
    if (input.hostId) throw errors.badRequest('A part in custody cannot be on a host');
    if (input.binId) throw errors.badRequest('A part in custody cannot be in a bin');
    return { binId: null, hostId: null, custodianId };
  }

  // SPARE / BROKEN / PENDING_DESTRUCTION
  if (input.hostId) {
    throw errors.badRequest('Only deployed parts can be assigned to a host');
  }
  if (input.custodianId) {
    throw errors.badRequest('Only custody states can have a custodian');
  }
  const binId = input.binId !== undefined ? input.binId : current.binId;
  return { binId, hostId: null, custodianId: null };
}

const partInclude = {
  manufacturer: true,
  partModel: true,
  bin: { include: { room: { include: { site: true } } } },
  category: true,
  host: true,
  custodian: { select: { id: true, username: true } },
  tags: { include: { tag: true } },
} satisfies Prisma.PartInclude;

type PartWithRelations = Prisma.PartGetPayload<{ include: typeof partInclude }>;
type BinWithSite = NonNullable<PartWithRelations['bin']>;
export type PartWithPath = Omit<PartWithRelations, 'tags'> & {
  bin: (BinWithSite & { fullPath?: string }) | null;
  tags: { id: string; name: string; color: string | null }[];
};

function binPath(bin: BinWithSite | null | undefined): string | null {
  if (!bin) return null;
  return `${bin.room.site.name}.${bin.room.name}.${bin.name}`;
}

function flattenTags(part: PartWithRelations): PartWithPath {
  const { tags, ...rest } = part;
  const out = rest as PartWithPath;
  if (out.bin) out.bin.fullPath = binPath(out.bin) ?? undefined;
  out.tags = tags.map((t) => ({
    id: t.tag.id,
    name: t.tag.name,
    color: t.tag.color,
  }));
  return out;
}

// Resolves a CreatePartRequest's partModelId — either the explicit one passed in, or looked up
// via (manufacturerId, mpn) shorthand that auto-creates a PartModel catalog row on first use.
// Exactly one of those two forms is required; the zod schema enforces that at the boundary.
async function resolvePartModel(
  tx: Tx,
  input: { partModelId?: string; manufacturerId?: string; mpn?: string },
): Promise<{ partModelId: string; manufacturerId: string }> {
  if (input.partModelId) {
    const pm = await tx.partModel.findUnique({ where: { id: input.partModelId } });
    if (!pm) throw errors.badRequest('Part model does not exist');
    return { partModelId: pm.id, manufacturerId: pm.manufacturerId };
  }
  if (input.manufacturerId && input.mpn) {
    const pm = await partModelsSvc.upsertByMpn(tx, {
      manufacturerId: input.manufacturerId,
      mpn: input.mpn,
    });
    return { partModelId: pm.id, manufacturerId: pm.manufacturerId };
  }
  throw errors.badRequest('Provide partModelId or both manufacturerId and mpn');
}

function buildWhere(q: PartListQuery): Prisma.PartWhereInput {
  const where: Prisma.PartWhereInput = {};
  if (q.state) where.state = q.state;
  if (q.binId) where.binId = q.binId;
  if (q.hostId) where.hostId = q.hostId;
  if (q.custodianId) where.custodianId = q.custodianId;
  if (q.manufacturerId) where.manufacturerId = q.manufacturerId;
  if (q.partModelId) where.partModelId = q.partModelId;
  if (q.categoryId) where.categoryId = q.categoryId;
  if (q.serialNumber) where.serialNumber = { contains: q.serialNumber };
  if (q.q) {
    where.OR = [
      { serialNumber: { contains: q.q } },
      { partModel: { mpn: { contains: q.q } } },
      { notes: { contains: q.q } },
    ];
  }
  if (q.tagId) where.tags = { some: { tagId: q.tagId } };

  const partModelFilter: Prisma.PartModelWhereInput = {};
  if (q.mpn) partModelFilter.mpn = { contains: q.mpn };
  if (q.eolOnly) partModelFilter.eolDate = { lt: new Date() };
  if (Object.keys(partModelFilter).length > 0) where.partModel = partModelFilter;

  return where;
}

export async function list(tx: Tx, q: PartListQuery) {
  const { page, pageSize } = q;
  const where = buildWhere(q);
  const [rows, total] = await Promise.all([
    tx.part.findMany({
      where,
      orderBy: { createdAt: 'desc' },
      include: partInclude,
      skip: (page - 1) * pageSize,
      take: pageSize,
    }),
    tx.part.count({ where }),
  ]);
  return { data: rows.map(flattenTags), page, pageSize, total };
}

export async function get(tx: Tx, id: string): Promise<PartWithPath | null> {
  const p = await tx.part.findUnique({ where: { id }, include: partInclude });
  return p ? flattenTags(p) : null;
}

export async function create(
  tx: Tx,
  input: CreatePartRequest,
  actor: Actor | null,
): Promise<PartWithPath> {
  const { partModelId, manufacturerId } = await resolvePartModel(tx, input);
  // If caller also supplied manufacturerId explicitly, it must match the part model's.
  if (input.manufacturerId && input.manufacturerId !== manufacturerId) {
    throw errors.badRequest('manufacturerId does not match the selected part model');
  }

  const state = input.state ?? 'SPARE';
  const location = resolveLocation(state, {
    binId: input.binId,
    hostId: input.hostId,
    custodianId: input.custodianId,
  });

  try {
    const p = await tx.part.create({
      data: {
        serialNumber: input.serialNumber,
        partModelId,
        manufacturerId,
        price: input.price ?? null,
        state,
        binId: location.binId,
        hostId: location.hostId,
        custodianId: location.custodianId,
        categoryId: input.categoryId ?? null,
        notes: input.notes ?? null,
      },
      include: partInclude,
    });
    await tx.partEvent.create({
      data: {
        partId: p.id,
        userId: actor?.id ?? null,
        type: 'CREATED',
        newValue: p.serialNumber,
      },
    });
    if (input.tagIds && input.tagIds.length > 0) {
      await tagsSvc.setPartTags(tx, p.id, input.tagIds, actor);
    }
    const refreshed = await tx.part.findUnique({ where: { id: p.id }, include: partInclude });
    return flattenTags(refreshed!);
  } catch (err) {
    if (err instanceof Prisma.PrismaClientKnownRequestError && err.code === 'P2002') {
      throw errors.conflict('Serial number already exists');
    }
    throw err;
  }
}

export async function update(
  tx: Tx,
  id: string,
  input: UpdatePartRequest,
  actor: Actor | null,
): Promise<PartWithPath> {
  const current = await tx.part.findUnique({ where: { id }, include: partInclude });
  if (!current) throw errors.notFound('Part');

  const data: Prisma.PartUpdateInput = {};
  if (input.serialNumber !== undefined) data.serialNumber = input.serialNumber;
  if (input.partModelId !== undefined) {
    const pm = await tx.partModel.findUnique({ where: { id: input.partModelId } });
    if (!pm) throw errors.badRequest('Part model does not exist');
    data.partModel = { connect: { id: pm.id } };
    // Keep denormalized manufacturerId consistent with the chosen model.
    data.manufacturer = { connect: { id: pm.manufacturerId } };
  }
  if (input.price !== undefined) data.price = input.price;
  if (input.state !== undefined) data.state = input.state;

  let nextBinId: string | null = current.binId;
  let nextHostId: string | null = current.hostId;
  let nextCustodianId: string | null = current.custodianId;
  const locationTouched =
    input.state !== undefined ||
    input.binId !== undefined ||
    input.hostId !== undefined ||
    input.custodianId !== undefined;
  if (locationTouched) {
    const nextState = input.state ?? (current.state as PartStateValue);
    const resolved = resolveLocation(
      nextState,
      {
        binId: input.binId,
        hostId: input.hostId,
        custodianId: input.custodianId,
      },
      {
        binId: current.binId,
        hostId: current.hostId,
        custodianId: current.custodianId,
      },
    );
    nextBinId = resolved.binId;
    nextHostId = resolved.hostId;
    nextCustodianId = resolved.custodianId;
    data.bin = resolved.binId ? { connect: { id: resolved.binId } } : { disconnect: true };
    data.host = resolved.hostId ? { connect: { id: resolved.hostId } } : { disconnect: true };
    data.custodian = resolved.custodianId
      ? { connect: { id: resolved.custodianId } }
      : { disconnect: true };
  }

  if (input.categoryId !== undefined) {
    data.category = input.categoryId
      ? { connect: { id: input.categoryId } }
      : { disconnect: true };
  }
  if (input.notes !== undefined) data.notes = input.notes;

  let part: PartWithRelations;
  try {
    part = await tx.part.update({ where: { id }, data, include: partInclude });
  } catch (err) {
    if (err instanceof Prisma.PrismaClientKnownRequestError) {
      if (err.code === 'P2025') throw errors.notFound('Part');
      if (err.code === 'P2002') throw errors.conflict('Serial number already exists');
    }
    throw err;
  }

  const userId = actor?.id ?? null;
  const events: Prisma.PartEventCreateManyInput[] = [];

  if (input.state !== undefined && input.state !== current.state) {
    events.push({
      partId: part.id,
      userId,
      type: 'STATE_CHANGED',
      field: 'state',
      oldValue: current.state,
      newValue: input.state,
    });
  }
  if (nextBinId !== current.binId) {
    events.push({
      partId: part.id,
      userId,
      type: 'LOCATION_CHANGED',
      field: 'bin',
      oldValue: binPath(current.bin),
      newValue: binPath(part.bin),
    });
  }
  if (nextHostId !== current.hostId) {
    events.push({
      partId: part.id,
      userId,
      type: 'LOCATION_CHANGED',
      field: 'host',
      oldValue: current.host?.name ?? null,
      newValue: part.host?.name ?? null,
    });
  }
  if (nextCustodianId !== current.custodianId) {
    events.push({
      partId: part.id,
      userId,
      type: 'LOCATION_CHANGED',
      field: 'custodian',
      oldValue: current.custodian?.username ?? null,
      newValue: part.custodian?.username ?? null,
    });
  }
  if (input.partModelId !== undefined && input.partModelId !== current.partModelId) {
    events.push({
      partId: part.id,
      userId,
      type: 'FIELD_UPDATED',
      field: 'partModel',
      oldValue: current.partModel.mpn,
      newValue: part.partModel.mpn,
    });
  }
  if (input.serialNumber !== undefined && input.serialNumber !== current.serialNumber) {
    events.push({
      partId: part.id,
      userId,
      type: 'FIELD_UPDATED',
      field: 'serialNumber',
      oldValue: current.serialNumber,
      newValue: input.serialNumber,
    });
  }
  if (input.categoryId !== undefined && input.categoryId !== current.categoryId) {
    events.push({
      partId: part.id,
      userId,
      type: 'FIELD_UPDATED',
      field: 'category',
      oldValue: current.category?.name ?? null,
      newValue: part.category?.name ?? null,
    });
  }
  if (input.price !== undefined && input.price !== current.price) {
    events.push({
      partId: part.id,
      userId,
      type: 'FIELD_UPDATED',
      field: 'price',
      oldValue: current.price?.toString() ?? null,
      newValue: input.price?.toString() ?? null,
    });
  }
  if (input.notes !== undefined && (input.notes ?? null) !== (current.notes ?? null)) {
    events.push({
      partId: part.id,
      userId,
      type: 'FIELD_UPDATED',
      field: 'notes',
      oldValue: current.notes ?? null,
      newValue: input.notes ?? null,
    });
  }

  if (events.length > 0) await tx.partEvent.createMany({ data: events });

  if (input.tagIds !== undefined) {
    await tagsSvc.setPartTags(tx, part.id, input.tagIds, actor);
    const refreshed = await tx.part.findUnique({ where: { id: part.id }, include: partInclude });
    return flattenTags(refreshed!);
  }

  return flattenTags(part);
}

export async function remove(tx: Tx, id: string) {
  try {
    await tx.part.delete({ where: { id } });
  } catch (err) {
    if (err instanceof Prisma.PrismaClientKnownRequestError) {
      if (err.code === 'P2025') throw errors.notFound('Part');
      if (err.code === 'P2003') {
        throw errors.conflict('Cannot delete: part is referenced by an FM or repair');
      }
    }
    throw err;
  }
}

export async function listEvents(tx: Tx, partId: string, q: PaginationQuery) {
  const { page, pageSize } = q;
  const [data, total] = await Promise.all([
    tx.partEvent.findMany({
      where: { partId },
      orderBy: { createdAt: 'desc' },
      include: { user: { select: { username: true } } },
      skip: (page - 1) * pageSize,
      take: pageSize,
    }),
    tx.partEvent.count({ where: { partId } }),
  ]);
  return { data, page, pageSize, total };
}

// Bulk mutation. Batches all writes inside a single transaction so partial failures roll back.
// Intentionally capped so callers can't accidentally lock the whole parts table.
export interface BulkPartsInput {
  ids: string[];
  state?: CreatePartRequest['state'];
  binId?: string | null;
  hostId?: string | null;
  addTagIds?: string[];
  removeTagIds?: string[];
}

const BULK_LIMIT = 500;

export async function bulkUpdate(tx: Tx, input: BulkPartsInput, actor: Actor | null) {
  if (input.ids.length === 0) throw errors.badRequest('No part ids supplied');
  if (input.ids.length > BULK_LIMIT) {
    throw errors.badRequest(`Bulk operations are limited to ${BULK_LIMIT} parts per call`);
  }

  const touched: string[] = [];
  for (const id of input.ids) {
    const patch: UpdatePartRequest = {};
    if (input.state !== undefined) patch.state = input.state;
    if (input.binId !== undefined) patch.binId = input.binId;
    if (input.hostId !== undefined) patch.hostId = input.hostId;
    if (Object.keys(patch).length > 0) {
      await update(tx, id, patch, actor);
    }
    if (input.addTagIds || input.removeTagIds) {
      const existing = await tx.partTag.findMany({ where: { partId: id }, select: { tagId: true } });
      const next = new Set(existing.map((r) => r.tagId));
      (input.addTagIds ?? []).forEach((t) => next.add(t));
      (input.removeTagIds ?? []).forEach((t) => next.delete(t));
      await tagsSvc.setPartTags(tx, id, [...next], actor);
    }
    touched.push(id);
  }
  return { updated: touched.length };
}