//
// Copyright 2023 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only
//

import Foundation
import GRDB
import LibSignalClient

class AuthorMergeObserver: RecipientMergeObserver {
    private let authorMergeHelper: AuthorMergeHelper

    init(authorMergeHelper: AuthorMergeHelper) {
        self.authorMergeHelper = authorMergeHelper
    }

    func willBreakAssociation(for recipient: SignalRecipient, mightReplaceNonnilPhoneNumber: Bool, tx: DBWriteTransaction) {
        guard mightReplaceNonnilPhoneNumber else {
            // This is only adding/removing a PNI, so there's nothing to do.
            return
        }
        guard let aciString = recipient.aciString, let phoneNumber = recipient.phoneNumber?.stringValue else {
            return
        }
        guard authorMergeHelper.shouldCleanUp(phoneNumber: phoneNumber, tx: tx) else {
            return
        }
        populateMissingAcis(phoneNumber: phoneNumber, aciString: aciString, tx: tx)
        authorMergeHelper.didCleanUp(phoneNumber: phoneNumber, tx: tx)
    }

    func didLearnAssociation(mergedRecipient: MergedRecipient, tx: DBWriteTransaction) {
        // As an performance optimization, don't assign missing ACIs unless we
        // must. When we learn an association, we don't need to assign ACIs because
        // we can still fetch based on phone number. When we *break* an
        // association, we must populate missing values because we'll no longer be
        // able to fetch based on the phone number.

        // As a further performance optimization, start a low-priority operation to
        // assign this ACI now that we know it. Hopefully this will finish before
        // the association is broken if and when some other ACI claims the number.
        // If it doesn't finish, things won't break, but they will require a slower
        // blocking migration instead.
        guard
            mergedRecipient.newRecipient.aciString != nil,
            let phoneNumber = mergedRecipient.newRecipient.phoneNumber?.stringValue
        else {
            return
        }
        authorMergeHelper.maybeJustLearnedAci(for: phoneNumber, tx: tx)
    }

    private func populateMissingAcis(phoneNumber: String, aciString: String, tx: DBWriteTransaction) {
        for table in AuthorDatabaseTable.all {
            let sql = """
                UPDATE "\(table.name)"
                SET "\(table.aciColumn)" = ?
                WHERE "\(table.phoneNumberColumn)" = ?
                AND "\(table.aciColumn)" IS NULL
            """
            let arguments: StatementArguments = [aciString, phoneNumber]
            SDSDB.shimOnlyBridge(tx).unwrapGrdbWrite.execute(sql: sql, arguments: arguments)
        }
        ModelReadCaches.shared.evacuateAllCaches()
    }
}

public struct AuthorDatabaseTable {
    public let name: String
    public let aciColumn: String
    public let phoneNumberColumn: String

    public static var all: [AuthorDatabaseTable] {
        return [
            AuthorDatabaseTable(
                name: OWSReaction.databaseTableName,
                aciColumn: OWSReaction.columnName(.reactorUUID),
                phoneNumberColumn: OWSReaction.columnName(.reactorE164)
            ),
            AuthorDatabaseTable(
                name: InteractionRecord.databaseTableName,
                aciColumn: InteractionRecord.columnName(.authorUUID),
                phoneNumberColumn: InteractionRecord.columnName(.authorPhoneNumber)
            ),
            AuthorDatabaseTable(
                name: "pending_read_receipts",
                aciColumn: "authorUuid",
                phoneNumberColumn: "authorPhoneNumber"
            ),
            AuthorDatabaseTable(
                name: "pending_viewed_receipts",
                aciColumn: "authorUuid",
                phoneNumberColumn: "authorPhoneNumber"
            )
        ]
    }
}