free-agents.ts

import { parseAgentId } from '../util/agent-id-parsing'

import type { CostMode } from './model-config'

/**
 * The cost mode that indicates FREE mode.
 * Only allowlisted agent+model combinations cost 0 credits in this mode.
 */
export const FREE_COST_MODE = 'free' as const

/**
 * Agents that are allowed to run in FREE mode.
 * Only these specific agents (and their expected models) get 0 credits in FREE mode.
 * This prevents abuse by users trying to use arbitrary agents for free.
 *
 * The mapping also specifies which models each agent is allowed to use in free mode.
 * If an agent uses a different model, it will be charged full credits.
 */
export const FREE_MODE_AGENT_MODELS: Record<string, Set<string>> = {
  // Root orchestrator
  'base2-free': new Set(['minimax/minimax-m2.5']),

  // File exploration agents
  'file-picker': new Set(['google/gemini-2.5-flash-lite']),
  'file-picker-max': new Set(['google/gemini-3.1-flash-lite-preview']),
  'file-lister': new Set(['google/gemini-3.1-flash-lite-preview']),

  // Research agents
  'researcher-web': new Set(['google/gemini-3.1-flash-lite-preview']),
  'researcher-docs': new Set(['google/gemini-3.1-flash-lite-preview']),

  // Command execution
  'basher': new Set(['google/gemini-3.1-flash-lite-preview']),

  // Editor for free mode
  'editor-lite': new Set(['minimax/minimax-m2.5']),

  // Code reviewer for free mode
  'code-reviewer-lite': new Set(['minimax/minimax-m2.5']),

  // Thinker for free mode
  'thinker-with-files-gemini': new Set(['google/gemini-3.1-pro-preview']),
}

/**
 * Agents that don't charge credits when credits would be very small (<5).
 *
 * These are typically lightweight utility agents that:
 * - Use cheap models (e.g., Gemini Flash)
 * - Have limited, programmatic capabilities
 * - Are frequently spawned as subagents
 *
 * Making them free avoids user confusion when they connect their own
 * Claude subscription (BYOK) but still see credit charges for non-Claude models.
 *
 * NOTE: This is separate from FREE_MODE_ALLOWED_AGENTS which is for the
 * explicit "free" cost mode. These agents get free credits only when
 * the cost would be trivial (<5 credits).
 */
export const FREE_TIER_AGENTS = new Set([
  'file-picker',
  'file-picker-max',
  'file-lister',
  'researcher-web',
  'researcher-docs',
])

/**
 * Check if the current cost mode is FREE mode.
 * In FREE mode, agents using allowed models cost 0 credits.
 */
export function isFreeMode(costMode: CostMode | string | undefined): boolean {
  return costMode === FREE_COST_MODE
}

/**
 * Check if a specific agent is allowed to use a specific model in FREE mode.
 * This is the strictest check - validates both the agent AND model combination.
 *
 * Returns true only if:
 * 1. The agent has a valid agent ID
 * 2. The agent is in the allowed free-mode agents list
 * 3. The agent is either internal or published by 'codebuff' (prevents spoofing)
 * 4. The model is in that agent's allowed model set
 */
export function isFreeModeAllowedAgentModel(
  fullAgentId: string,
  model: string,
): boolean {
  const { publisherId, agentId } = parseAgentId(fullAgentId)

  // Must have a valid agent ID
  if (!agentId) return false

  // Must be either internal (no publisher) or from codebuff
  if (publisherId && publisherId !== 'codebuff') return false

  // Get the allowed models for this agent
  const allowedModels = FREE_MODE_AGENT_MODELS[agentId]
  if (!allowedModels) return false

  // Empty set means programmatic agent (no LLM calls expected)
  // For these, any model check should fail (they shouldn't be making LLM calls)
  if (allowedModels.size === 0) return false

  // Exact match first
  if (allowedModels.has(model)) return true

  // OpenRouter may return dated variants (e.g. "minimax/minimax-m2.5-20260211")
  // so also check if the returned model starts with any allowed model prefix.
  for (const allowed of allowedModels) {
    if (model.startsWith(allowed + '-')) return true
  }

  return false
}

/**
 * Check if an agent should be free (no credit charge) for small requests.
 * This is separate from FREE mode - these agents get free credits only
 * when the cost would be trivial (<5 credits).
 *
 * Handles all agent ID formats:
 * - 'file-picker'
 * - 'file-picker@1.0.0'
 * - 'codebuff/file-picker@0.0.2'
 */
export function isFreeAgent(fullAgentId: string): boolean {
  const { publisherId, agentId } = parseAgentId(fullAgentId)

  // Must have a valid agent ID
  if (!agentId) return false

  // Must be in the free tier agents list
  if (!FREE_TIER_AGENTS.has(agentId)) return false

  // Must be either internal (no publisher) or from codebuff
  // This prevents publisher spoofing attacks
  if (publisherId && publisherId !== 'codebuff') return false

  return true
}