import type { ProviderOptions } from '@ai-sdk/provider-utils'
import { application } from '@application'
import type { AiPlugin } from '@cherrystudio/ai-core'
import { MAX_TOOL_CALLS, MIN_TOOL_CALLS } from '@main/ai/constants'
import { type Assistant, DEFAULT_ASSISTANT_SETTINGS } from '@shared/data/types/assistant'
import type { Model } from '@shared/data/types/model'
import type { Provider } from '@shared/data/types/provider'
import { isFunctionCallingModel } from '@shared/utils/model'
import { stepCountIs, type StopCondition, type ToolSet, type UIMessage } from 'ai'

import { collectFileAttachments } from '../../../messages/attachmentRouting'
import type { FileAttachmentRef } from '../../../messages/attachmentTypes'
import { createHttpTraceFetch } from '../../../observability'
import { providerToAiSdkConfig } from '../../../provider/config'
import { resolveAiSdkProviderId, resolveEffectiveEndpoint } from '../../../provider/endpoint'
import type { RequestContext } from '../../../tools/adapters/aiSdk/context'
import { applyDeferExposition } from '../../../tools/adapters/aiSdk/exposition/applyDeferExposition'
import { syncMcpToolsToRegistry } from '../../../tools/adapters/aiSdk/mcp/mcpTools'
import { resolveAssistantMcpToolIds } from '../../../tools/adapters/aiSdk/mcp/resolveAssistantMcpTools'
import { registry } from '../../../tools/adapters/aiSdk/registry'
import { createAiRepair } from '../../../tools/adapters/aiSdk/repair'
import type { ToolEntry } from '../../../tools/adapters/aiSdk/types'
import type { AiBaseRequest, CallOverrides } from '../../../types/requests'
import { filterStandardParams } from '../../../utils/modelParameters'
import {
  buildCapabilityProviderOptions,
  extractAiSdkStandardParams,
  mergeCustomProviderParameters
} from '../../../utils/options'
import { getCustomParameters } from '../../../utils/reasoning'
import type { AgentLoopHooks, AgentOptions } from '../loop'
import { assembleSystemPrompt } from './assembleSystemPrompt'
import { buildTelemetry } from './buildTelemetry'
import { resolveCapabilities } from './capabilities'
import { collectFromFeatures } from './collectFromFeatures'
import type { RequestFeature } from './feature'
import { INTERNAL_FEATURES } from './features'
import { type NativeFileSupport, resolveNativeFileSupport } from './nativeFileSupport'
import type { RequestScope, SdkConfig } from './scope'

export interface BuildAgentParamsInput {
  request: AiBaseRequest & {
    chatId?: string
    messageId?: string
    messages?: UIMessage[]
  }
  signal: AbortSignal | undefined
  provider: Provider
  model: Model
  assistant?: Assistant
  /** Caller-supplied features merged after `INTERNAL_FEATURES`. */
  extraFeatures?: readonly RequestFeature[]
}

export interface BuiltAgentParams {
  sdkConfig: SdkConfig
  tools: ToolSet | undefined
  plugins: AiPlugin<any, any>[]
  system: string | undefined
  options: AgentOptions
  /** Hook contributions from features — caller composes with its own internal hooks. */
  hookParts: ReadonlyArray<Partial<AgentLoopHooks>>
  /** Attachment routing inputs for `prepareChatMessages` (chat path). */
  nativeFileSupport: NativeFileSupport
  fileAttachments: FileAttachmentRef[]
}

export async function buildAgentParams(input: BuildAgentParamsInput): Promise<BuiltAgentParams> {
  const { request, signal, provider, model, assistant, extraFeatures } = input

  const sdkConfig = await resolveSdkConfig(provider, model)
  applyHttpTrace(sdkConfig, request.chatId, model)
  const fileAttachments = collectFileAttachments(request.messages)
  const hasFileAttachments = fileAttachments.length > 0
  const { tools, deferredEntries, mcpToolIds } = canModelConsumeTools(model)
    ? await resolveTools(request, assistant, model, hasFileAttachments)
    : { tools: undefined, deferredEntries: [] as ToolEntry[], mcpToolIds: new Set<string>() }
  const capabilities = assistant ? resolveCapabilities(model, provider, assistant) : undefined

  const { endpointType } = resolveEffectiveEndpoint(provider, model)
  const aiSdkProviderId = resolveAiSdkProviderId(provider, endpointType)
  const nativeFileSupport = resolveNativeFileSupport(provider, model, aiSdkProviderId)

  const requestContext: RequestContext = {
    requestId: request.messageId ?? crypto.randomUUID(),
    topicId: request.chatId,
    assistant,
    abortSignal: signal,
    fileAttachments
  }

  const scope: RequestScope = {
    request,
    signal,
    registry,
    assistant,
    model,
    provider,
    capabilities,
    sdkConfig,
    endpointType,
    aiSdkProviderId,
    requestContext,
    mcpToolIds,
    hasFileAttachments
  }

  const features = extraFeatures?.length ? [...INTERNAL_FEATURES, ...extraFeatures] : INTERNAL_FEATURES
  const contributions = collectFromFeatures(scope, features)

  const system = await assembleSystemPrompt({ assistant, model, tools, deferredEntries })
  const options = buildAgentOptions(scope, contributions.stopConditions)

  return {
    sdkConfig,
    tools,
    plugins: contributions.modelAdapters,
    system,
    options,
    hookParts: contributions.hookParts,
    nativeFileSupport,
    fileAttachments
  }
}

async function resolveSdkConfig(provider: Provider, model: Model): Promise<SdkConfig> {
  return {
    ...(await providerToAiSdkConfig(provider, model)),
    modelId: model.apiModelId ?? model.id
  }
}

export function applyHttpTrace(sdkConfig: SdkConfig, topicId: string | undefined, model: Model): void {
  if (!application.get('PreferenceService').get('app.developer_mode.enabled')) return
  const settings = sdkConfig.providerSettings
  settings.fetch = createHttpTraceFetch(settings.fetch ?? globalThis.fetch, {
    topicId,
    modelName: model.name ?? model.id
  })
}

/**
 * Skip the entire tool-resolution path (registry sync, defer exposition,
 * meta-tool injection) when the model can't consume tools at all. Without
 * this gate, a non-function-calling model gets the meta-tools + system-
 * prompt section pushed at it for nothing — pure token waste with no way
 * for the model to act on it.
 *
 * "Can consume" means the model supports native function calling (the
 * provider's tool API).
 */
function canModelConsumeTools(model: Model): boolean {
  return isFunctionCallingModel(model)
}

/**
 * Tool selection: pick MCP ids (caller wins, else derived from assistant),
 * sync the MCP entries into the registry, then materialise the active
 * `ToolSet` via `applies` predicates and defer exposition.
 */
async function resolveTools(
  request: BuildAgentParamsInput['request'],
  assistant: Assistant | undefined,
  model: Model,
  hasFileAttachments: boolean
): Promise<{
  tools: ToolSet | undefined
  deferredEntries: ToolEntry[]
  mcpToolIds: ReadonlySet<string>
}> {
  let mcpIdList = request.mcpToolIds
  if (!mcpIdList && request.assistantId) {
    mcpIdList = await resolveAssistantMcpToolIds(request.assistantId)
  }
  const mcpToolIds = new Set(mcpIdList ?? [])
  if (mcpToolIds.size) {
    // Scope the registry sync to servers that actually own a selected tool —
    // avoids paying the per-server `listTools` round-trip for every active
    // server when only one was picked for this request.
    await syncMcpToolsToRegistry(undefined, { selectedToolIds: mcpToolIds })
  }

  const activeEntries = registry.selectActive({ assistant, mcpToolIds, hasFileAttachments })
  let tools: ToolSet | undefined
  if (activeEntries.length > 0) {
    tools = {}
    for (const entry of activeEntries) tools[entry.name] = entry.tool
  }
  // First-class client tools (no `execute`) supplied per request by assistant-less
  // callers (the API gateway). Merged here so they share the registry/defer-exposition
  // path instead of being mutated onto raw SDK params.
  const clientTools = request.callOverrides?.tools
  if (clientTools && Object.keys(clientTools).length > 0) {
    tools = { ...tools, ...clientTools }
  }
  const exposed = applyDeferExposition(tools, registry, model.contextWindow)
  return { tools: exposed.tools, deferredEntries: exposed.deferredEntries, mcpToolIds }
}

/**
 * Assemble `AgentOptions`: capability-driven providerOptions overlaid with
 * the user's customParameters (split into AI-SDK standard params vs
 * provider-scoped params), per-call headers/maxRetries, stop-after-N-tools,
 * and the tool-call repair function.
 */
function buildAgentOptions(scope: RequestScope, featureStopConditions: StopCondition<ToolSet>[]): AgentOptions {
  const { assistant, capabilities, model, provider, sdkConfig, requestContext, request, aiSdkProviderId } = scope

  let providerOptions =
    assistant && capabilities ? buildCapabilityProviderOptions(assistant, model, provider, capabilities) : {}
  let standardParams: Partial<Record<string, unknown>> = {}
  if (assistant) {
    const customParams = getCustomParameters(assistant)
    if (Object.keys(customParams).length > 0) {
      const split = extractAiSdkStandardParams(customParams)
      standardParams = filterStandardParams(split.standardParams, model)
      providerOptions = mergeCustomProviderParameters(providerOptions, split.providerParams, aiSdkProviderId)
    }
  }

  // Highest-precedence per-request overrides (assistant-less callers, e.g. the API gateway).
  const callOverrides = request.callOverrides
  const overridden = applyCallOverrides({ standardParams, providerOptions }, callOverrides, model)
  standardParams = overridden.standardParams
  providerOptions = overridden.providerOptions as typeof providerOptions

  const { headers, maxRetries } = request.requestOptions ?? {}
  const baseStopWhen = assistant ? resolveStopWhenForAssistant(assistant) : undefined
  const stopWhen = composeStopWhen(baseStopWhen, featureStopConditions)
  const telemetry = buildTelemetry(scope)

  return {
    maxRetries: maxRetries ?? 0,
    ...(stopWhen && { stopWhen }),
    ...(headers && { headers }),
    ...(callOverrides?.toolChoice && { toolChoice: callOverrides.toolChoice }),
    ...(Object.keys(providerOptions).length > 0 && { providerOptions }),
    ...(telemetry && { telemetry }),
    ...standardParams,
    context: requestContext,
    repairToolCall: createAiRepair({
      providerId: sdkConfig.providerId,
      providerSettings: sdkConfig.providerSettings,
      modelId: sdkConfig.modelId
    })
  }
}

/**
 * Merge per-request `callOverrides` (highest precedence) onto base sampling params +
 * providerOptions. Sampling passes through `filterStandardParams` for model-capability
 * gating (e.g. topK dropped for Gemini 3.x / Claude 4.7); providerOptions merge
 * per-provider so other providers' keys aren't clobbered. Exported for unit testing.
 */
export function applyCallOverrides(
  base: { standardParams: Partial<Record<string, unknown>>; providerOptions: ProviderOptions },
  callOverrides: CallOverrides | undefined,
  model: Model
): { standardParams: Partial<Record<string, unknown>>; providerOptions: ProviderOptions } {
  if (!callOverrides) return base

  const sampling: Partial<Record<string, unknown>> = {}
  if (callOverrides.temperature !== undefined) sampling.temperature = callOverrides.temperature
  if (callOverrides.maxOutputTokens !== undefined) sampling.maxOutputTokens = callOverrides.maxOutputTokens
  if (callOverrides.topP !== undefined) sampling.topP = callOverrides.topP
  if (callOverrides.topK !== undefined) sampling.topK = callOverrides.topK
  if (callOverrides.stopSequences !== undefined) sampling.stopSequences = callOverrides.stopSequences
  const standardParams = { ...base.standardParams, ...filterStandardParams(sampling, model) }

  let providerOptions = base.providerOptions
  if (callOverrides.providerOptions) {
    const merged: ProviderOptions = { ...providerOptions }
    for (const [pid, opts] of Object.entries(callOverrides.providerOptions)) {
      merged[pid] = { ...merged[pid], ...opts }
    }
    providerOptions = merged
  }
  return { standardParams, providerOptions }
}

/** Mirrors the AI SDK / `ToolLoopAgent` default step cap (`stepCountIs(20)`). Used as the fallback
 *  bound when a feature contributes a `stopWhen` but no assistant base supplies one — passing any
 *  explicit `stopWhen` otherwise suppresses the SDK default and leaves the tool loop uncapped. */
const SDK_DEFAULT_STEP_COUNT = 20

/**
 * OR the assistant's step cap with feature-contributed stop conditions. An explicit `stopWhen`
 * suppresses the loop's default `stepCountIs(20)`, so when a feature contributes a condition but no
 * assistant base supplies a cap, fall back to that default — otherwise an assistant-less tool loop
 * (e.g. a `chatId`-only steer-yield request) would run unbounded.
 */
export function composeStopWhen(
  baseStopWhen: StopCondition<ToolSet> | undefined,
  featureStopConditions: StopCondition<ToolSet>[]
): StopCondition<ToolSet> | StopCondition<ToolSet>[] | undefined {
  if (featureStopConditions.length === 0) return baseStopWhen
  const base = baseStopWhen ?? stepCountIs(SDK_DEFAULT_STEP_COUNT)
  return [base, ...featureStopConditions]
}

function resolveStopWhenForAssistant(assistant: Assistant): ReturnType<typeof stepCountIs> {
  const enableMaxToolCalls = assistant.settings?.enableMaxToolCalls ?? DEFAULT_ASSISTANT_SETTINGS.enableMaxToolCalls
  if (!enableMaxToolCalls) {
    return stepCountIs(DEFAULT_ASSISTANT_SETTINGS.maxToolCalls)
  }
  const raw = assistant.settings?.maxToolCalls
  const valid = raw !== undefined && raw >= MIN_TOOL_CALLS && raw <= MAX_TOOL_CALLS
  const count = valid ? raw : DEFAULT_ASSISTANT_SETTINGS.maxToolCalls
  return stepCountIs(count)
}
