/** Package-owned tool-pipeline invariants. @module @deepseek-ai/dsh-tools/invariant */

import type { Context } from 'cordis'
import type { InvariantFailure, InvariantInstaller } from '@deepseek-ai/dsh-invariants'
import type { ToolExecution, ToolExecutionResult } from './index.ts'

const PACKAGE_NAME = '@deepseek-ai/dsh-tools'

/** Cordis companion plugin name. */
export const name = 'tools-invariant'
/** Service required before the companion can reserve package ownership. */
export const inject = ['invariants']

type ToolStage = 'pre' | 'execute' | 'post'

/** Validate the immutable final execution/result snapshot. */
function validateResult(
  exec: Readonly<ToolExecution>,
  result: Readonly<ToolExecutionResult>,
  fail: InvariantFailure,
): void {
  if (!Object.isFrozen(exec)) fail('tools/result execution must be frozen before publication')
  if (!Object.isFrozen(result) || !Object.isFrozen(result.content)) {
    fail('tools/result outcome and content must be frozen before publication')
  }
  if (exec.name.length === 0 || String(exec.callId).length === 0) {
    fail('tools/result execution must carry non-empty name and callId')
  }
}

/** Install monotonic pipeline and final-snapshot checks. */
const install: InvariantInstaller = (ctx, fail) => {
  const stages = new WeakMap<object, ToolStage>()
  ctx.on('internal/dispatch', (_mode, eventName, args) => {
    if (eventName === 'tools/pre-execute') {
      const exec = args[0] as ToolExecution
      if (stages.has(exec)) fail('tools/pre-execute repeated for one execution')
      stages.set(exec, 'pre')
      return
    }
    if (eventName === 'tools/execute') {
      const exec = args[0] as ToolExecution
      if (stages.get(exec) !== 'pre') fail('tools/execute must follow tools/pre-execute')
      stages.set(exec, 'execute')
      return
    }
    if (eventName === 'tools/post-execute') {
      const exec = args[0] as ToolExecution
      const previous = stages.get(exec)
      if (previous !== 'pre' && previous !== 'execute') {
        fail('tools/post-execute must follow tools/pre-execute or tools/execute')
      }
      stages.set(exec, 'post')
      return
    }
    if (eventName !== 'tools/result') return
    const [exec, result] = args as [Readonly<ToolExecution>, Readonly<ToolExecutionResult>]
    validateResult(exec, result, fail)
    stages.delete(exec)
  }, { global: true })
}

/**
 * Register the tools invariant companion.
 * @param ctx - Cordis context carrying the invariant service.
 * @returns the installed registration's disposer after setup succeeds.
 */
export const apply = (ctx: Context): Promise<() => void> =>
  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))