// Project + model persistence layer.
//
// Stores the full SysMLModel as a JSON snapshot per version, plus a changelog
// of applied ops. Reads return the latest snapshot; writes apply ops
// server-side and write a new snapshot + changelog row atomically.

import { prisma } from "./client";
import { applyOps } from "../sync/applyOps";
import { fromFixture } from "../sysml/fromFixture";
import { aristotleFixture } from "../fixtures/aristotle";
import type { SysMLModel } from "../sysml/model";
import type { ModelOp } from "../sync/ops";

export interface LoadResult {
  model: SysMLModel;
  version: number;
}

export async function loadProject(projectId: string): Promise<LoadResult> {
  // Auto-seed: if the project doesn't exist (or has no snapshot), bootstrap
  // it from the Aristotle fixture so the editor route always has data.
  const seeded = await ensureSeeded(projectId);
  const snapshot = await prisma.modelSnapshot.findFirst({
    where: { projectId: seeded.projectId },
    orderBy: { version: "desc" },
  });
  if (!snapshot) {
    throw new Error(`Project ${projectId} has no snapshots after seed — should not happen`);
  }
  return {
    model: JSON.parse(snapshot.json) as SysMLModel,
    version: snapshot.version,
  };
}

export interface ApplyResult {
  applied: boolean;
  model: SysMLModel;
  version: number;
  idMapping: Record<string, string>;
  errors: Array<{ opIndex: number; code: string; message: string }>;
}

export async function applyOpsToProject(
  projectId: string,
  ops: ModelOp[],
  expectedVersion: number | undefined,
  reason?: string
): Promise<ApplyResult> {
  return prisma.$transaction(async tx => {
    const latest = await tx.modelSnapshot.findFirst({
      where: { projectId },
      orderBy: { version: "desc" },
    });
    if (!latest) throw new Error(`No snapshot for project ${projectId}`);

    if (expectedVersion !== undefined && expectedVersion !== latest.version) {
      // Optimistic-concurrency miss; caller must resync.
      return {
        applied: false,
        model: JSON.parse(latest.json) as SysMLModel,
        version: latest.version,
        idMapping: {},
        errors: [{ opIndex: -1, code: "VERSION_MISMATCH", message: `Expected version ${expectedVersion}, server is ${latest.version}` }],
      };
    }

    const currentModel = JSON.parse(latest.json) as SysMLModel;
    const result = applyOps(currentModel, ops);
    if (!result.applied) {
      return {
        applied: false,
        model: currentModel,
        version: latest.version,
        idMapping: {},
        errors: result.errors,
      };
    }

    const newVersion = latest.version + 1;
    await tx.modelSnapshot.create({
      data: {
        projectId,
        version: newVersion,
        json: JSON.stringify(result.model),
      },
    });
    await tx.changelogEntry.create({
      data: {
        projectId,
        version: newVersion,
        ops: JSON.stringify(ops),
        reason,
      },
    });

    return {
      applied: true,
      model: result.model,
      version: newVersion,
      idMapping: result.idMapping,
      errors: [],
    };
  });
}

// ─── Seeding ─────────────────────────────────────────────────────────────

async function ensureSeeded(projectId: string): Promise<{ projectId: string }> {
  const existing = await prisma.project.findUnique({ where: { id: projectId } });
  if (existing) {
    // Make sure there's at least one snapshot
    const snapCount = await prisma.modelSnapshot.count({ where: { projectId } });
    if (snapCount > 0) return { projectId };
  }

  // Bootstrap with the Aristotle fixture
  const seedModel = fromFixture(aristotleFixture);
  await prisma.project.upsert({
    where: { id: projectId },
    update: {},
    create: {
      id: projectId,
      name: aristotleFixture.project.name,
      scope: aristotleFixture.project.scope,
      tagline: aristotleFixture.project.tagline,
    },
  });
  await prisma.modelSnapshot.create({
    data: {
      projectId,
      version: 1,
      json: JSON.stringify(seedModel),
    },
  });

  // Auto-create an opening Socrates thread so the dock has somewhere to talk.
  // Socrates' opening turn is generated lazily on first GET (so we don't
  // pin a model selection to seed time).
  await prisma.socratesThread.create({
    data: {
      projectId,
      title: "Active thread · " + aristotleFixture.project.name,
      status: "open",
    },
  });

  return { projectId };
}

// ─── Socrates threads ────────────────────────────────────────────────────

export async function getActiveThread(projectId: string): Promise<{ id: string; title: string | null; messages: Array<{ id: string; role: string; content: string; createdAt: Date }> } | null> {
  const thread = await prisma.socratesThread.findFirst({
    where: { projectId, status: "open" },
    orderBy: { updatedAt: "desc" },
    include: { messages: { orderBy: { createdAt: "asc" } } },
  });
  if (!thread) return null;
  return {
    id: thread.id,
    title: thread.title,
    messages: thread.messages.map(m => ({
      id: m.id,
      role: m.role,
      content: m.content,
      createdAt: m.createdAt,
    })),
  };
}