/**
 * Template interpolation for response prefix.
 *
 * Supports variables like `{model}`, `{provider}`, `{thinkingLevel}`, etc.
 * Variables are case-insensitive and unresolved ones remain as literal text.
 */

export type ResponsePrefixContext = {
  /** Short model name (e.g., "gpt-5.2", "claude-opus-4-6") */
  model?: string;
  /** Full model ID including provider (e.g., "openai-codex/gpt-5.2") */
  modelFull?: string;
  /** Provider name (e.g., "openai-codex", "anthropic") */
  provider?: string;
  /** Current thinking level (e.g., "high", "low", "off") */
  thinkingLevel?: string;
  /** Agent identity name */
  identityName?: string;
};

// Regex pattern for template variables: {variableName} or {variable.name}
const TEMPLATE_VAR_PATTERN = /\{([a-zA-Z][a-zA-Z0-9.]*)\}/g;

/**
 * Interpolate template variables in a response prefix string.
 *
 * @param template - The template string with `{variable}` placeholders
 * @param context - Context object with values for interpolation
 * @returns The interpolated string, or undefined if template is undefined
 *
 * @example
 * resolveResponsePrefixTemplate("[{model} | think:{thinkingLevel}]", {
 *   model: "gpt-5.2",
 *   thinkingLevel: "high"
 * })
 * // Returns: "[gpt-5.2 | think:high]"
 */
export function resolveResponsePrefixTemplate(
  template: string | undefined,
  context: ResponsePrefixContext,
): string | undefined {
  if (!template) {
    return undefined;
  }

  return template.replace(TEMPLATE_VAR_PATTERN, (match, varName: string) => {
    const normalizedVar = varName.toLowerCase();

    switch (normalizedVar) {
      case "model":
        return context.model ?? match;
      case "modelfull":
        return context.modelFull ?? match;
      case "provider":
        return context.provider ?? match;
      case "thinkinglevel":
      case "think":
        return context.thinkingLevel ?? match;
      case "identity.name":
      case "identityname":
        return context.identityName ?? match;
      default:
        // Leave unrecognized variables as-is
        return match;
    }
  });
}

/**
 * Extract short model name from a full model string.
 *
 * Strips:
 * - Provider prefix (e.g., "openai/" from "openai/gpt-5.2")
 * - Date suffixes (e.g., "-20260205" from "claude-opus-4-6-20260205")
 * - Common version suffixes (e.g., "-latest")
 *
 * @example
 * extractShortModelName("openai-codex/gpt-5.2") // "gpt-5.2"
 * extractShortModelName("claude-opus-4-6-20260205") // "claude-opus-4-6"
 * extractShortModelName("gpt-5.2-latest") // "gpt-5.2"
 */
export function extractShortModelName(fullModel: string): string {
  // Strip provider prefix
  const slash = fullModel.lastIndexOf("/");
  const modelPart = slash >= 0 ? fullModel.slice(slash + 1) : fullModel;

  // Strip date suffixes (YYYYMMDD format)
  return modelPart.replace(/-\d{8}$/, "").replace(/-latest$/, "");
}

/**
 * Check if a template string contains any template variables.
 */
export function hasTemplateVariables(template: string | undefined): boolean {
  if (!template) {
    return false;
  }
  // Reset lastIndex since we're using a global regex
  TEMPLATE_VAR_PATTERN.lastIndex = 0;
  return TEMPLATE_VAR_PATTERN.test(template);
}
