import { v4 as uuid } from 'uuid';

import { AbstractPowerSyncDatabase, PowerSyncBackendConnector } from '@powersync/web';

export type DemoConfig = {
    backendUrl: string;
    powersyncUrl: string;
};

enum CheckpointMode {
    CUSTOM = 'custom',
    MANAGED = 'managed'
}

const USER_ID_STORAGE_KEY = 'ps_user_id';

export class StackRenderConnector implements PowerSyncBackendConnector {
    readonly config: DemoConfig;
    readonly userId: string;

    private _clientId: string | null;

    constructor() {
        let userId = localStorage.getItem(USER_ID_STORAGE_KEY);
        if (!userId) {
            userId = uuid();
            localStorage.setItem(USER_ID_STORAGE_KEY, userId);
        }
        this.userId = userId;
        this._clientId = null;

        this.config = {
            backendUrl: import.meta.env.VITE_BACKEND_URL as string,
            powersyncUrl: import.meta.env.VITE_POWERSYNC_URL as string
        };
    }

    async fetchCredentials() {
        const tokenEndpoint = 'api/auth/token';
        const res = await fetch(`${this.config.backendUrl}/${tokenEndpoint}?user_id=${this.userId}`);

        if (!res.ok) {
            throw new Error(`Received ${res.status} from ${tokenEndpoint}: ${await res.text()}`);
        }

        const body = await res.json();

        return {
            endpoint: this.config.powersyncUrl,
            token: body.token
        };
    }

    async uploadData(database: AbstractPowerSyncDatabase): Promise<void> {
 
        const transaction = await database.getNextCrudTransaction();
 
        if (!transaction) {
            return;
        }

        if (!this._clientId) {
            this._clientId = await database.getClientId();
        }

        try {
            let batch: any[] = [];
            for (let operation of transaction.crud) {
                let payload = {
                    op: operation.op,
                    table: operation.table,
                    id: operation.id,
                    data: operation.opData
                };
                batch.push(payload);
            }

            const response = await fetch(`${this.config.backendUrl}/api/data`, {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json'
                },
                body: JSON.stringify({ batch })
            });

            if (!response.ok) {
                throw new Error(`Received ${response.status} from /api/data: ${await response.text()}`);
            }

            await transaction.complete(
                import.meta.env.VITE_CHECKPOINT_MODE == CheckpointMode.CUSTOM
                    ? await this.getCheckpoint(this._clientId)
                    : undefined
            );
        } catch (ex: any) {
            console.debug(ex);
            throw ex;
        }
    }

    /**
     * Gets a custom Write Checkpoint from the backend. This is only used
     * when custom Write Checkpoints are enabled during build.
     */
    async getCheckpoint(client_id: string) {
        
        const r = await fetch(`${this.config.backendUrl}/api/data/checkpoint`, {
            method: 'PUT',
            headers: {
                'Content-Type': 'application/json'
            },
            body: JSON.stringify({
                user_id: this.userId,
                client_id: client_id
            })
        });
        const j = await r.json();
        return j.checkpoint as string;
    }
}