/**
 * HologramAgent loop: surface recall as a SYSTEM section instead of history.
 *
 * Why this exists
 * ---------------
 * `dsh-memory` injects per-turn recall through the `agent/pre-step` waterfall,
 * and that hook can only return `messages`. Whatever it adds therefore lands in
 * conversation history as a user message — the model reads its own memory as if
 * a user had said it. `systemPrompt.context` cannot fix this either: that hook
 * runs before the turn text is known (documented in dsh-memory's own module
 * note), so it can only render input-INDEPENDENT text.
 *
 * The loop's own `preStep` is the first place that has BOTH the assembled
 * prompt and the claimed messages for this turn. So the swap point is here:
 * let the existing pre-step hooks run unchanged, then move the recall block out
 * of `messages` and into `assembly.sections`. The memory becomes part of the
 * system prompt for that turn, and the user message never enters history.
 *
 * Coupling
 * --------
 * None, deliberately. We do not import the memory plugin or match its name; we
 * recognise the *shape* every snapshot-style injector already uses
 * (`source.sections = [{ name, text }]`), which is the same shape
 * `dsh-time-context` emits. Anything a plugin chose to label that way is
 * promoted; everything else passes through untouched.
 */

import { AgentLoop } from '@deepseek-ai/dsh-agent-loop'

/** Suffix appended to the promoted section name, keeping provenance visible. */
const PROMOTED_SUFFIX = ':system'

/**
 * Split one message's `source.sections` out of the message itself.
 *
 * A message is promoted only when it is a pure carrier: snapshot form, a
 * non-empty sections array, and no content blocks of its own. A message that
 * carries both text and sections is the plugin saying "this is a user-visible
 * turn" — touching it would delete something the plugin meant to keep.
 *
 * @param {object} message a user message from a pre-step decision
 * @returns {{text: string, name: string} | null}
 */
function promotedSection(message) {
  const source = message === null || typeof message !== 'object' ? undefined : message.source
  if (source === null || typeof source !== 'object') return null
  if (source.form !== 'snapshot') return null
  if (!Array.isArray(source.sections) || source.sections.length === 0) return null
  const blocks = Array.isArray(message.content) ? message.content : []
  if (blocks.length > 0) return null
  const parts = []
  for (const section of source.sections) {
    if (section !== null && typeof section === 'object' && typeof section.text === 'string' && section.text !== '') {
      parts.push(section.text)
    }
    else if (typeof section === 'string' && section !== '') parts.push(section)
  }
  if (parts.length === 0) return null
  const name = typeof source.kind === 'string' && source.kind !== '' ? source.kind : 'memory'
  return { text: parts.join('\n\n'), name }
}

/**
 * Rewrite one pre-step decision so snapshot sections live in the prompt.
 *
 * The returned object is a NEW decision: `super.step()` keeps the one it
 * received, and the loop's phase bookkeeping reads `assembly` off whatever it
 * is handed. Mutating in place would work today and would silently break the
 * first time the loop reuses a decision.
 *
 * @param {object} decision the decision returned by the pre-step waterfall
 * @returns {object} the same decision shape with promoted sections moved
 */
export function promoteSnapshotSections(decision) {
  if (decision === null || typeof decision !== 'object') return decision
  if (decision.kind === 'reject') return decision
  const messages = Array.isArray(decision.messages) ? decision.messages : []
  const assembly = decision.assembly
  if (assembly === null || typeof assembly !== 'object' || !Array.isArray(assembly.sections)) return decision

  const kept = []
  const promoted = []
  for (const message of messages) {
    const section = promotedSection(message)
    if (section === null) kept.push(message)
    else promoted.push(section)
  }
  if (promoted.length === 0) return decision

  const sections = [...assembly.sections]
  const seen = new Set(sections.map((section) => section.name))
  for (const section of promoted) {
    // A name collision means some other producer already owns that slot. The
    // prompt layer throws on duplicates, so suffix rather than overwrite:
    // dropping the content would hide memory with no visible failure.
    let name = `${section.name}${PROMOTED_SUFFIX}`
    for (let n = 2; seen.has(name); n += 1) name = `${section.name}${PROMOTED_SUFFIX}${n}`
    seen.add(name)
    // `interpolate: false` is mandatory, not cosmetic: recalled notes are free
    // text and may legitimately contain `{{...}}`, which the strict interpolator
    // rejects with `unknown prompt variable` (measured — dsh-memory hit this).
    sections.push({ name, text: section.text, interpolate: false })
  }

  return { ...decision, messages: kept, assembly: { ...assembly, sections } }
}

/**
 * The headless AgentLoop, with snapshot sections promoted into the prompt.
 *
 * No constructor and no static `inject`: the parent already registers the
 * turnBoundary + inbox projections, calls `agents.setFactory(this)`, and
 * declares the `{{provider}}` / `{{model}}` variables. Re-declaring any of them
 * here would be the bug — `setFactory` throws if a factory is already
 * registered, so a second registration is exactly what breaks startup.
 */
export class HologramAgentLoop extends AgentLoop {
  /**
   * Prepare one agent, then wrap its pre-step seam.
   *
   * Patching the *instance* (not the prototype) is deliberate: the prototype is
   * shared with every agent the base class creates, including ones this plugin
   * must not touch. An own property shadows it for this agent only.
   *
   * @param {...unknown} args forwarded verbatim to the parent
   * @returns {{agent: object, signal: AbortSignal, publish: Function}}
   */
  prepare(...args) {
    const prepared = super.prepare(...args)
    const agent = prepared === null || typeof prepared !== 'object' ? undefined : prepared.agent
    if (agent === undefined || typeof agent.preStep !== 'function') return prepared
    const original = agent.preStep.bind(agent)
    agent.preStep = async (target, position) => promoteSnapshotSections(await original(target, position))
    return prepared
  }
}

export default HologramAgentLoop