-- Receipt-to-batch attribution for loan repayments. When another same-lender,
-- same-amount loan batch was ever exported or had receipts, a matched receipt
-- alone does not prove which batch it paid; settlement then requires an
-- independently reviewed attribution bound to the exact transaction fingerprint
-- and to the receipt evidence (verification and manual-proposal ids) reviewed.

-- CreateTable
CREATE TABLE "loan_receipt_attributions" (
    "id" UUID NOT NULL,
    "payment_batch_id" UUID NOT NULL,
    "fingerprint" VARCHAR(64) NOT NULL,
    "key_id" VARCHAR(64) NOT NULL,
    "verification_ids" JSONB NOT NULL,
    "manual_proposal_ids" JSONB NOT NULL,
    "competitor_batch_ids" JSONB NOT NULL,
    "basis_kind" VARCHAR(32) NOT NULL,
    "basis_note" VARCHAR(1000) NOT NULL,
    "exclusion_note" VARCHAR(1000) NOT NULL,
    "status" VARCHAR(16) NOT NULL DEFAULT 'proposed',
    "proposed_by" UUID NOT NULL,
    "proposed_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
    "reviewed_by" UUID,
    "reviewed_at" TIMESTAMP(3),
    "review_note" VARCHAR(500),
    "superseded_at" TIMESTAMP(3),

    CONSTRAINT "loan_receipt_attributions_pkey" PRIMARY KEY ("id"),
    CONSTRAINT "loan_receipt_attributions_status_check" CHECK ("status" IN ('proposed', 'approved', 'rejected', 'superseded')),
    CONSTRAINT "loan_receipt_attributions_basis_kind_check" CHECK ("basis_kind" IN
      ('customer_serial', 'bank_memo', 'bank_written_confirmation', 'competitors_resolved')),
    CONSTRAINT "loan_receipt_attributions_notes_check" CHECK (
      char_length(btrim("basis_note")) >= 10 AND char_length(btrim("exclusion_note")) >= 10),
    CONSTRAINT "loan_receipt_attributions_evidence_check" CHECK (
      jsonb_typeof("verification_ids") = 'array' AND jsonb_array_length("verification_ids") > 0
      AND jsonb_typeof("manual_proposal_ids") = 'array'),
    CONSTRAINT "loan_receipt_attributions_competitors_check" CHECK (
      jsonb_typeof("competitor_batch_ids") = 'array' AND jsonb_array_length("competitor_batch_ids") > 0),
    CONSTRAINT "loan_receipt_attributions_review_check" CHECK (
      ("status" = 'proposed' AND "reviewed_by" IS NULL AND "reviewed_at" IS NULL)
      OR ("status" IN ('approved', 'rejected') AND "reviewed_by" IS NOT NULL AND "reviewed_at" IS NOT NULL)
      OR "status" = 'superseded'),
    CONSTRAINT "loan_receipt_attributions_superseded_check" CHECK (("status" = 'superseded') = ("superseded_at" IS NOT NULL)),
    CONSTRAINT "loan_receipt_attributions_independent_check" CHECK (
      "reviewed_by" IS NULL OR "reviewed_by" <> "proposed_by")
);

-- CreateIndex
CREATE INDEX "loan_receipt_attributions_batch_fingerprint_idx" ON "loan_receipt_attributions"("payment_batch_id", "fingerprint");

-- At most one open or approved attribution per batch; rejected and superseded rows stay as history.
CREATE UNIQUE INDEX "loan_receipt_attributions_one_active_per_batch"
  ON "loan_receipt_attributions"("payment_batch_id") WHERE "status" IN ('proposed', 'approved');

-- AddForeignKey
ALTER TABLE "loan_receipt_attributions" ADD CONSTRAINT "loan_receipt_attributions_payment_batch_id_fkey" FOREIGN KEY ("payment_batch_id") REFERENCES "payment_batches"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
ALTER TABLE "loan_receipt_attributions" ADD CONSTRAINT "loan_receipt_attributions_proposed_by_fkey" FOREIGN KEY ("proposed_by") REFERENCES "employees"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
ALTER TABLE "loan_receipt_attributions" ADD CONSTRAINT "loan_receipt_attributions_reviewed_by_fkey" FOREIGN KEY ("reviewed_by") REFERENCES "employees"("id") ON DELETE RESTRICT ON UPDATE CASCADE;

-- History is append-only: proposed -> approved/rejected/superseded, approved ->
-- superseded (when the receipt or competitor set changed); nothing else, no deletes.
CREATE FUNCTION guard_loan_receipt_attribution_history() RETURNS trigger LANGUAGE plpgsql AS $$
BEGIN
  IF TG_OP = 'DELETE' THEN RAISE EXCEPTION 'loan receipt attribution history is immutable'; END IF;
  IF OLD."status" IN ('rejected', 'superseded') THEN RAISE EXCEPTION 'closed loan receipt attribution is immutable'; END IF;
  IF OLD."status" = 'approved' AND (NEW."status" <> 'superseded' OR NEW."reviewed_by" IS DISTINCT FROM OLD."reviewed_by"
     OR NEW."reviewed_at" IS DISTINCT FROM OLD."reviewed_at" OR NEW."review_note" IS DISTINCT FROM OLD."review_note") THEN
    RAISE EXCEPTION 'approved loan receipt attribution can only be superseded';
  END IF;
  IF OLD."status" = 'proposed' AND NEW."status" IN ('proposed', 'superseded')
     AND (NEW."reviewed_by" IS NOT NULL OR NEW."reviewed_at" IS NOT NULL OR NEW."review_note" IS NOT NULL) THEN
    RAISE EXCEPTION 'unreviewed loan receipt attribution cannot carry review fields';
  END IF;
  IF NEW."payment_batch_id" <> OLD."payment_batch_id" OR NEW."fingerprint" <> OLD."fingerprint" OR NEW."key_id" <> OLD."key_id"
     OR NEW."verification_ids" <> OLD."verification_ids" OR NEW."manual_proposal_ids" <> OLD."manual_proposal_ids"
     OR NEW."competitor_batch_ids" <> OLD."competitor_batch_ids" OR NEW."basis_kind" <> OLD."basis_kind"
     OR NEW."basis_note" <> OLD."basis_note" OR NEW."exclusion_note" <> OLD."exclusion_note"
     OR NEW."proposed_by" <> OLD."proposed_by" OR NEW."proposed_at" <> OLD."proposed_at" THEN
    RAISE EXCEPTION 'loan receipt attribution proposal is immutable';
  END IF;
  RETURN NEW;
END $$;
CREATE TRIGGER loan_receipt_attribution_history BEFORE UPDATE OR DELETE ON "loan_receipt_attributions"
  FOR EACH ROW EXECUTE FUNCTION guard_loan_receipt_attribution_history();