import { updateCase, reconsiderCompletedEpisode } from "@/lib/graph/orchestrator.js";
import { applyValidatedProposal } from "@/lib/graph/apply-proposal.js";
import { prepareCompletedEpisode } from "@/lib/graph/episode-preparation.js";
import { updateCaseEpisodeRequestSchema } from "@/lib/graph/schema.js";

function mapFailureStatus(result) {
  switch (result?.stage) {
    case "request_validation":
    case "graph_validation":
      return 400;
    case "provider":
      return 502;
    case "proposal_validation":
    case "proposal_compatibility":
    case "application":
      return 422;
    case "result_validation":
      return 500;
    default:
      return 500;
  }
}

function buildFailureResponse(result) {
  return {
    success: false,
    stage: result?.stage ?? "internal",
    error: result?.error ?? "Update case failed",
    validationErrors: result?.validationErrors,
    graphValidationErrors: result?.graphValidationErrors,
    proposalErrors: result?.proposalErrors,
    providerErrors: result?.providerErrors,
    errors: result?.errors,
    diagnostics: result?.diagnostics,
  };
}

export async function POST(request) {
  try {
    const body = await request.json();
    const isEpisodeMode = body?.episodeMode === true;

    if (isEpisodeMode) {
      const parsed = updateCaseEpisodeRequestSchema.safeParse(body);
      if (!parsed.success) {
        return Response.json(
          {
            success: false,
            stage: "request_validation",
            error: "Invalid episode request",
            validationErrors: parsed.error.issues,
          },
          { status: 400 },
        );
      }

      return await handleEpisodeMode(body.situationGraph, body);
    }

    const result = await updateCase(body, { applyProposal: true });

    if (result.success) {
      return Response.json(result, { status: 200 });
    }

    return Response.json(buildFailureResponse(result), {
      status: mapFailureStatus(result),
    });
  } catch (error) {
    if (error instanceof SyntaxError) {
      return Response.json(
        {
          success: false,
          stage: "request_validation",
          error: "Invalid JSON request body",
        },
        { status: 400 },
      );
    }

    return Response.json(
      {
        success: false,
        stage: "internal",
        error: "Internal server error",
      },
      { status: 500 },
    );
  }
}

/** Server-side completed-episode reconsideration flow. */
async function handleEpisodeMode(situationGraph, body) {
  const prepared = prepareCompletedEpisode({
    situationGraph,
    targetNodeId: body.targetNodeId,
    contributions: body.contributions ?? [],
    findings: body.findings,
  });

  if (!prepared?.turns?.length && !prepared?.eligibleCanonicalFindings?.length) {
    return Response.json(
      { success: false, stage: "preparation", error: "no_episodic_content" },
      { status: 400 },
    );
  }

  const reasoning = await reconsiderCompletedEpisode(prepared);
  if (!reasoning.success) {
    return Response.json(
      buildFailureResponse(reasoning),
      { status: mapFailureStatus(reasoning) },
    );
  }

  const application = await applyValidatedProposal({
    situationGraph,
    proposal: reasoning.proposal,
    evidenceContext: {
      isCompletedEpisode: true,
      episodeEvidence: prepared,
    },
  });

  if (!application.success) {
    return Response.json(
      buildFailureResponse(application),
      { status: mapFailureStatus(application) },
    );
  }

  return Response.json({
    success: true,
    updatedSituationGraph: application.updatedSituationGraph,
    proposal: reasoning.proposal,
  }, { status: 200 });
}