export interface AgentPromptEnvelope {
  text: string
  displayText?: string
  inspectSummary?: string
  inspectTrace?: string
}

const ENVELOPE_MARKER = 'sootsim-agent-prompt-v1'

function cleanPromptText(value: string | undefined): string {
  return typeof value === 'string' ? value.trim() : ''
}

export function encodeAgentPromptEnvelope(input: AgentPromptEnvelope): string {
  const text = cleanPromptText(input.text)
  if (!text) return ''
  const displayText = cleanPromptText(input.displayText)
  const inspectSummary = cleanPromptText(input.inspectSummary)
  const inspectTrace = cleanPromptText(input.inspectTrace)
  const needsEnvelope =
    !!inspectSummary ||
    !!inspectTrace ||
    /[\r\n]/.test(text) ||
    (!!displayText && displayText !== text)
  if (!needsEnvelope) return text
  return JSON.stringify({
    __sootsimAgentPrompt: ENVELOPE_MARKER,
    text,
    displayText,
    inspectSummary,
    inspectTrace,
  })
}

export function decodeAgentPromptEnvelope(line: string): AgentPromptEnvelope | null {
  const trimmed = cleanPromptText(line)
  if (!trimmed) return null
  try {
    const parsed = JSON.parse(trimmed) as {
      __sootsimAgentPrompt?: unknown
      text?: unknown
      displayText?: unknown
      inspectSummary?: unknown
      inspectTrace?: unknown
    }
    if (parsed.__sootsimAgentPrompt !== ENVELOPE_MARKER) {
      return { text: trimmed }
    }
    const text = cleanPromptText(
      typeof parsed.text === 'string' ? parsed.text : undefined,
    )
    if (!text) return null
    const displayText = cleanPromptText(
      typeof parsed.displayText === 'string' ? parsed.displayText : undefined,
    )
    const inspectSummary = cleanPromptText(
      typeof parsed.inspectSummary === 'string' ? parsed.inspectSummary : undefined,
    )
    const inspectTrace = cleanPromptText(
      typeof parsed.inspectTrace === 'string' ? parsed.inspectTrace : undefined,
    )
    return {
      text,
      ...(displayText ? { displayText } : {}),
      ...(inspectSummary ? { inspectSummary } : {}),
      ...(inspectTrace ? { inspectTrace } : {}),
    }
  } catch {
    return { text: trimmed }
  }
}