package repositories

import (
	"fmt"

	"nearle/models"

	"gorm.io/gorm"
)

// Releasing a product from the admin catalogue to the shops.
//
// Until this existed there was no such step. The import created a
// `productlocations` row and membership of that table *was* publication, so a
// product reached every store the moment it was imported — unpriced, because
// pricing had not happened yet. That is how the platform ended up with a
// catalogue of products a till could not ring up.
//
// Two rules, both enforced here rather than in the console, because a rule that
// only exists in a form is a rule that holds until somebody calls the API:
//
//  1. **A product cannot be published without a price.** An unpriced product
//     reaching a shop is the exact failure this separation prevents — the POS
//     catalogue sends it down as `is_active: false` and it cannot be sold.
//  2. **Publishing covers every outlet the tenant runs.** A price is a
//     business-level decision, and a product live at one branch and absent from
//     another is a support call nobody can explain.

// PublishProduct releases one product to every outlet of a tenant at the given
// price, creating the store link where it does not exist yet.
//
// Idempotent: publishing an already-published product re-prices it and leaves
// the original `publishedat` alone, so "when did this go live" survives a
// second click.
func (r *productRepository) PublishProduct(tenantID, productID int, price, taxPercent float64) (int, error) {
	if tenantID <= 0 || productID <= 0 {
		return 0, fmt.Errorf("tenantid and productid are required")
	}
	if price <= 0 {
		return 0, fmt.Errorf("set a price before publishing — a product with no price cannot be sold at a till")
	}
	// Zero is a legitimate rate — plenty of staples are zero-rated — so it
	// cannot double as "not specified". Negative is refused rather than stored:
	// three products already carry taxpercent -1, which yields negative tax
	// under either convention.
	if taxPercent < 0 {
		return 0, fmt.Errorf("tax percentage cannot be negative")
	}

	var affected int
	err := r.db.Transaction(func(tx *gorm.DB) error {
		// The tenant's outlets are read here rather than accepted from the
		// caller. A console that sent its own list could publish to a subset by
		// omission and nobody would notice which shop was missing.
		var locationIDs []int
		if err := tx.Raw(`
			SELECT locationid FROM tenantlocations
			WHERE tenantid = ? AND LOWER(COALESCE(status,'active')) <> 'inactive'
			ORDER BY locationid`, tenantID).Scan(&locationIDs).Error; err != nil {
			return err
		}
		if len(locationIDs) == 0 {
			return fmt.Errorf("this business has no active outlet to publish to")
		}

		// Verify the product belongs to this tenant before writing anything
		// against it. Everything below is keyed on (tenantid, productid), but a
		// caller naming another tenant's product would otherwise create rows for
		// a product that is not theirs.
		var owned int64
		if err := tx.Raw(`SELECT COUNT(1) FROM products WHERE productid = ? AND tenantid = ?`,
			productID, tenantID).Scan(&owned).Error; err != nil {
			return err
		}
		if owned == 0 {
			return fmt.Errorf("product %d does not belong to this business", productID)
		}

		for _, locationID := range locationIDs {
			// COALESCE on publishedat keeps the first release date through a
			// re-publish; NOW() only applies to a row that has never been live.
			res := tx.Exec(`
				UPDATE productlocations
				SET price = ?, publishedat = COALESCE(publishedat, NOW()), updated = NOW()
				WHERE tenantid = ? AND locationid = ? AND productid = ?`,
				price, tenantID, locationID, productID)
			if res.Error != nil {
				return res.Error
			}
			if res.RowsAffected == 0 {
				if err := tx.Exec(`
					INSERT INTO productlocations
					  (tenantid, locationid, productid, price, status, publishedat, created, updated)
					VALUES (?, ?, ?, ?, 'Active', NOW(), NOW(), NOW())`,
					tenantID, locationID, productID, price).Error; err != nil {
					return err
				}
			}
			affected++
		}

		// The master price follows, so an outlet that has no row of its own
		// still reads the right figure through the COALESCE fallback in
		// GetProducts.
		return tx.Exec(`UPDATE products SET retailprice = ?, taxpercent = ?, updated = NOW()
		                WHERE productid = ? AND tenantid = ?`,
			price, taxPercent, productID, tenantID).Error
	})

	return affected, err
}

// UnpublishProduct withdraws a product from every shop.
//
// Clears `publishedat` and keeps the rows. Deleting them would lose the price,
// the stock ledger's link and any history, and a product pulled from sale for a
// week should come back the way it left.
func (r *productRepository) UnpublishProduct(tenantID, productID int) (int, error) {
	if tenantID <= 0 || productID <= 0 {
		return 0, fmt.Errorf("tenantid and productid are required")
	}

	res := r.db.Exec(`
		UPDATE productlocations SET publishedat = NULL, updated = NOW()
		WHERE tenantid = ? AND productid = ? AND publishedat IS NOT NULL`,
		tenantID, productID)
	return int(res.RowsAffected), res.Error
}

// PublishPricedLocations releases the rows an import has just created, at the
// one branch it imported into.
//
// The publish gate exists to stop an unpriced product reaching a till that
// would ring it up at zero. An import from a spreadsheet CARRIES the price — it
// is on the row this writes — so the gate's condition is already met, and
// leaving these rows unpublished asks somebody to click a button that can only
// answer "yes" seventeen times.
//
// It was not a harmless extra step. Nothing in the backend filters on
// `publishedat`, so the products were already on sale in the customer app while
// the merchant's own store catalogue — the one screen that does read it —
// showed nothing. The shopkeeper could not see what their shoppers could buy.
//
// Three things keep this honest:
//
//   - `price > 0` is checked in SQL, not by the caller. A row that somehow
//     arrived unpriced stays unpublished, which is the rule the gate is for.
//   - COALESCE keeps the first release date, so re-importing does not rewrite
//     the history of a product that has been on sale for months.
//   - Only the named branch. PublishProduct releases to every outlet a tenant
//     runs and that is right for a deliberate release; an import names one
//     branch, and quietly stocking the others would put products in shops
//     nobody chose.
func (r *productRepository) PublishPricedLocations(refs []models.ProductLocationRef) error {
	if len(refs) == 0 {
		return nil
	}
	for _, ref := range refs {
		if err := r.db.Exec(`
			UPDATE productlocations
			SET publishedat = COALESCE(publishedat, NOW()), updated = NOW()
			WHERE tenantid = ? AND locationid = ? AND productid = ?
			  AND COALESCE(price, 0) > 0`,
			ref.Tenantid, ref.Locationid, ref.Productid).Error; err != nil {
			return err
		}
	}
	return nil
}