<?php

namespace ChargeForms\Includes\Integrations;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Thin wrapper around Mailchimp's Marketing API v3 — every method here is a
 * single HTTP call with no ChargeForms-specific decision-making (which list,
 * which fields to map, retry policy); that logic lives in
 * Mailchimp_Integration, which is the only caller. Kept separate so the
 * "how do I talk to Mailchimp" concern is independently testable from "what
 * do we send it," the same split this codebase already uses for
 * Stripe_Gateway/Paypal_Gateway vs. the submission-handling code that calls
 * them.
 */
class Mailchimp_Client {

	/**
	 * Mailchimp API keys are always suffixed with the account's datacenter,
	 * e.g. `abc123def456-us21` — the API is hosted per-datacenter
	 * (`https://us21.api.mailchimp.com/...`), so a key that doesn't parse
	 * cleanly can never produce a valid base URL; callers get a WP_Error
	 * rather than a request to a guessed/wrong host.
	 */
	private static function datacenter( $api_key ) {
		$pos = strrpos( (string) $api_key, '-' );
		return ( false !== $pos && $pos < strlen( $api_key ) - 1 ) ? substr( $api_key, $pos + 1 ) : '';
	}

	/** MD5 of the lowercased email — Mailchimp's own addressing scheme for a list member resource (`/lists/{id}/members/{subscriber_hash}`), documented behavior, not a ChargeForms convention. */
	public static function subscriber_hash( $email ) {
		return md5( strtolower( trim( (string) $email ) ) );
	}

	private static function request( $api_key, $method, $path, $body = null ) {
		$dc = self::datacenter( $api_key );
		if ( '' === $dc ) {
			return new \WP_Error( 'chargeforms_mailchimp_bad_key', __( 'This does not look like a valid Mailchimp API key (missing the "-usXX" datacenter suffix).', 'chargeforms' ) );
		}

		$args = [
			'method'  => $method,
			'timeout' => 12,
			'headers' => [
				'Authorization' => 'Basic ' . base64_encode( 'chargeforms:' . $api_key ), // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_encode -- HTTP Basic auth encoding, not obfuscation; Mailchimp accepts any non-empty username.
				'Content-Type'  => 'application/json',
			],
		];
		if ( null !== $body ) {
			$args['body'] = wp_json_encode( $body );
		}

		$response = wp_remote_request( "https://{$dc}.api.mailchimp.com/3.0{$path}", $args );

		if ( is_wp_error( $response ) ) {
			return $response;
		}

		$code = wp_remote_retrieve_response_code( $response );
		$data = json_decode( wp_remote_retrieve_body( $response ), true );

		if ( $code >= 400 ) {
			// Mailchimp's error payload always has a human-readable "detail"
			// (e.g. "This account is set to only accept subscribed members
			// through opt-in forms") — surfacing that instead of a bare
			// status code is what makes Api_Log actually useful for
			// diagnosing WHY a subscribe failed.
			$message = is_array( $data ) && ! empty( $data['detail'] ) ? $data['detail'] : sprintf( /* translators: %d: HTTP status code */ __( 'Mailchimp returned an unexpected error (HTTP %d).', 'chargeforms' ), $code );
			return new \WP_Error( 'chargeforms_mailchimp_api_error', $message, [ 'status' => $code, 'body' => $data ] );
		}

		return is_array( $data ) ? $data : [];
	}

	/** Connection test — used by the "Test Connection" button on Global Settings > Integrations and to gate whether the per-form list dropdown even attempts to load. */
	public static function ping( $api_key ) {
		$result = self::request( $api_key, 'GET', '/ping' );
		return is_wp_error( $result ) ? $result : true;
	}

	/** @return array<int, array{id: string, name: string}>|\WP_Error */
	public static function get_lists( $api_key ) {
		$result = self::request( $api_key, 'GET', '/lists?count=100&fields=lists.id,lists.name' );
		if ( is_wp_error( $result ) ) {
			return $result;
		}
		$lists = [];
		foreach ( $result['lists'] ?? [] as $list ) {
			$lists[] = [ 'id' => $list['id'] ?? '', 'name' => $list['name'] ?? '' ];
		}
		return $lists;
	}

	/**
	 * Creates the member if new, updates them if they already exist —
	 * idempotent by design (PUT to the subscriber_hash resource), so a
	 * resubmission or an autosaved draft that later converts never creates
	 * a duplicate contact. `status_if_new` only takes effect on first
	 * creation; resubmitting never silently downgrades an existing member
	 * who has since unsubscribed (Mailchimp rejects mismatched `status`
	 * changes made this way on purpose — a compliance safeguard this
	 * client deliberately doesn't try to work around).
	 */
	public static function upsert_member( $api_key, $list_id, $email, array $merge_fields, $status_if_new ) {
		$body = [
			'email_address' => $email,
			'status_if_new' => $status_if_new,
		];
		if ( ! empty( $merge_fields ) ) {
			$body['merge_fields'] = $merge_fields;
		}
		return self::request( $api_key, 'PUT', '/lists/' . rawurlencode( $list_id ) . '/members/' . self::subscriber_hash( $email ), $body );
	}

	/**
	 * Separate endpoint, not part of upsert_member()'s body — Mailchimp's
	 * member-upsert PUT does not reliably apply a `tags` array to an
	 * EXISTING member (only ever on first creation in some API versions),
	 * so tags are always applied via this dedicated call to work
	 * correctly on both new and returning subscribers alike.
	 */
	public static function set_tags( $api_key, $list_id, $email, array $tag_names ) {
		if ( empty( $tag_names ) ) {
			return true;
		}
		$tags  = array_map( function ( $name ) {
			return [ 'name' => $name, 'status' => 'active' ];
		}, $tag_names );
		$result = self::request( $api_key, 'POST', '/lists/' . rawurlencode( $list_id ) . '/members/' . self::subscriber_hash( $email ) . '/tags', [ 'tags' => $tags ] );
		return is_wp_error( $result ) ? $result : true;
	}
}