func loadConfig()

in Sources/Hub/Hub.swift [170:240]
56 lines of code
11 McCabe index (conditional complexity)

    func loadConfig(
        modelFolder: URL,
        hubApi: HubApi = .shared
    ) async throws -> Configurations {
        do {
            // Load required configurations
            let modelConfigURL = modelFolder.appending(path: "config.json")
            guard FileManager.default.fileExists(atPath: modelConfigURL.path) else {
                throw Hub.HubClientError.configurationMissing("config.json")
            }

            let modelConfig = try hubApi.configuration(fileURL: modelConfigURL)

            let tokenizerDataURL = modelFolder.appending(path: "tokenizer.json")
            guard FileManager.default.fileExists(atPath: tokenizerDataURL.path) else {
                throw Hub.HubClientError.configurationMissing("tokenizer.json")
            }

            let tokenizerData = try hubApi.configuration(fileURL: tokenizerDataURL)

            // Load tokenizer config (optional)
            var tokenizerConfig: Config? = nil
            let tokenizerConfigURL = modelFolder.appending(path: "tokenizer_config.json")
            if FileManager.default.fileExists(atPath: tokenizerConfigURL.path) {
                tokenizerConfig = try hubApi.configuration(fileURL: tokenizerConfigURL)
            }

            // Check for chat template and merge if available
            // Prefer .jinja template over .json template
            var chatTemplate: String? = nil
            let chatTemplateJinjaURL = modelFolder.appending(path: "chat_template.jinja")
            let chatTemplateJsonURL = modelFolder.appending(path: "chat_template.json")

            if FileManager.default.fileExists(atPath: chatTemplateJinjaURL.path) {
                // Try to load .jinja template as plain text
                chatTemplate = try? String(contentsOf: chatTemplateJinjaURL, encoding: .utf8)
            } else if FileManager.default.fileExists(atPath: chatTemplateJsonURL.path),
                      let chatTemplateConfig = try? hubApi.configuration(fileURL: chatTemplateJsonURL)
            {
                // Fall back to .json template
                chatTemplate = chatTemplateConfig.chatTemplate.string()
            }

            if let chatTemplate {
                // Create or update tokenizer config with chat template
                if var configDict = tokenizerConfig?.dictionary() {
                    configDict["chat_template"] = .init(chatTemplate)
                    tokenizerConfig = Config(configDict)
                } else {
                    tokenizerConfig = Config(["chat_template": chatTemplate])
                }
            }

            return Configurations(
                modelConfig: modelConfig,
                tokenizerConfig: tokenizerConfig,
                tokenizerData: tokenizerData
            )
        } catch let error as Hub.HubClientError {
            throw error
        } catch {
            if let nsError = error as NSError? {
                if nsError.domain == NSCocoaErrorDomain, nsError.code == NSFileReadNoSuchFileError {
                    throw Hub.HubClientError.fileSystemError(error)
                } else if nsError.domain == "NSJSONSerialization" {
                    throw Hub.HubClientError.parseError("Invalid JSON format: \(nsError.localizedDescription)")
                }
            }
            throw Hub.HubClientError.fileSystemError(error)
        }
    }