import Foundation

final class FeishuService {
    private let baseURL = "https://open.feishu.cn/open-apis"
    private let session: URLSession
    private let decoder: JSONDecoder

    init(session: URLSession = .shared) {
        self.session = session
        let decoder = JSONDecoder()
        decoder.keyDecodingStrategy = .convertFromSnakeCase
        self.decoder = decoder
    }

    func fetchBugs(
        config: AppConfig,
        assigneeName: String,
        accessToken: String
    ) async throws -> [Bug] {
        var allRecords: [RecordItem] = []
        var pageToken: String?

        repeat {
            let page = try await fetchPage(
                appToken: config.appToken,
                tableId: config.tableId,
                pageToken: pageToken,
                accessToken: accessToken
            )
            allRecords.append(contentsOf: page.items)
            pageToken = page.hasMore ? page.pageToken : nil
        } while pageToken != nil

        return allRecords
            .map { BugMapper.map($0, config: config) }
            .filter { bug in
                bug.assignee.localizedCaseInsensitiveContains(assigneeName)
            }
    }

    func fetchRecordCount(
        appToken: String,
        tableId: String,
        accessToken: String
    ) async throws -> Int {
        let page = try await fetchPage(
            appToken: appToken,
            tableId: tableId,
            pageToken: nil,
            pageSize: 1,
            accessToken: accessToken
        )
        return page.total ?? page.items.count
    }

    private func fetchPage(
        appToken: String,
        tableId: String,
        pageToken: String?,
        pageSize: Int = 500,
        accessToken: String
    ) async throws -> RecordListData {
        var components = URLComponents(
            string: "\(baseURL)/bitable/v1/apps/\(appToken)/tables/\(tableId)/records"
        )!
        var queryItems = [URLQueryItem(name: "page_size", value: String(pageSize))]
        if let pageToken {
            queryItems.append(URLQueryItem(name: "page_token", value: pageToken))
        }
        components.queryItems = queryItems

        var request = URLRequest(url: components.url!)
        request.httpMethod = "GET"
        request.setValue("Bearer \(accessToken)", forHTTPHeaderField: "Authorization")
        request.timeoutInterval = 30

        let (data, response) = try await session.data(for: request)
        guard let httpResponse = response as? HTTPURLResponse else {
            throw FeishuError.networkError(nil)
        }
        if httpResponse.statusCode == 401 {
            throw FeishuError.unauthorized
        }

        let apiResponse: FeishuAPIResponse<RecordListData>
        do {
            apiResponse = try decoder.decode(FeishuAPIResponse<RecordListData>.self, from: data)
        } catch {
            throw FeishuError.decodingError(error)
        }

        guard apiResponse.code == 0, let pageData = apiResponse.data else {
            throw FeishuError.apiError(code: apiResponse.code, message: apiResponse.msg)
        }
        return pageData
    }
}