/**
 * Pure opencode `Event` → normalized `AgentEvent` translation.
 *
 * Extracted (v2.7 audit reshape) from `OpenCodeServerBackend.dispatchEvent` /
 * `handleUpdatedPart` and the file-local helpers. NO I/O, no timers, no DB, no
 * `byOpencodeId` — every function here is a deterministic transform over its
 * arguments (the dedup state is caller-owned and mutated in place, mirroring the
 * `acp-event-map.ts` `priorSnapshots` pattern). This is the unit-testable core; the
 * backend keeps the routing + side effects (watchdog, usage persistence, settle).
 *
 * Depends only on SDK TYPES + AcpToolSnapshot — safe to import anywhere.
 */
import type { Event, Part, ToolPart, ToolState } from '@opencode-ai/sdk/v2/client';
import type { ToolCallStatus } from '@agentclientprotocol/sdk';
import type { AcpToolSnapshot } from '../acp-tool-snapshot.js';
import type { AgentEvent } from '../agent-backend.js';

/** Per-(opencode session) dedup state the part-stream classifiers read + mutate. */
export interface DedupState {
  /** dedup gate: `${type}:${id}` added on delta, deleted-and-tested on updated. */
  streamedPartKeys: Set<string>;
  /** partID → 'text' | 'reasoning', so a delta with a non-'reasoning' field is still classed right. */
  partTypeById: Map<string, string>;
}

/** Strip opencode-dcp plugin tags that render as literal text in the UI. */
export function stripDcpTags(s: string): string {
  return s.replace(/<dcp-message-id>[^<]*<\/dcp-message-id>/g, '');
}

/** Extract the opencode sessionID an event belongs to, across event shapes.
 *  Most carry `properties.sessionID`; `message.part.updated` nests it under
 *  `properties.part.sessionID`. Returns null when the event has no session
 *  (the per-session loop then leaves it to dispatchEvent, which drops it). */
export function eventSessionId(ev: Event): string | null {
  const props = (ev as { properties?: unknown }).properties;
  if (!props || typeof props !== 'object') return null;
  if (ev.type === 'message.part.updated') {
    const part = (props as { part?: { sessionID?: string } }).part;
    return part?.sessionID ?? null;
  }
  return (props as { sessionID?: string }).sessionID ?? null;
}

/** Ported verbatim from Paseo opencode-agent.ts: id → message-id fallback → null. */
export function resolvePartDedupeKey(part: { id: string; messageID: string }, type: string): string | null {
  if (part.id.trim().length > 0) return `${type}:${part.id}`;
  if (part.messageID.trim().length > 0) return `${type}:message:${part.messageID}`;
  return null;
}

export function mapToolStatus(s: ToolState['status'] | undefined): ToolCallStatus | null {
  switch (s) {
    case 'pending':
      return 'pending';
    case 'running':
      return 'in_progress';
    case 'completed':
      return 'completed';
    case 'error':
      return 'failed';
    default:
      return null;
  }
}

/** opencode ToolPart → ACP-shaped snapshot (reuses the existing persist/render path). */
export function toolPartToSnapshot(part: ToolPart): AcpToolSnapshot {
  const state = part.state;
  let rawInput: unknown;
  let rawOutput: unknown;
  let title: string | undefined;
  if (state) {
    if ('input' in state) rawInput = (state as { input?: unknown }).input;
    if ('output' in state) rawOutput = (state as { output?: unknown }).output;
    else if ('error' in state) rawOutput = (state as { error?: unknown }).error;
    if ('title' in state) title = (state as { title?: string }).title;
  }
  return {
    toolCallId: part.callID,
    title: title ?? part.tool,
    kind: null,
    status: mapToolStatus(state?.status),
    rawInput,
    rawOutput,
  };
}

// ─── session.next.tool.* snapshot builders ───────────────────────────────────

/** `session.next.tool.called` → an in-progress tool_call snapshot. */
export function toolCalledSnapshot(p: { callID: string; tool: string; input: unknown }): AcpToolSnapshot {
  return {
    toolCallId: p.callID,
    title: p.tool,
    kind: null,
    status: 'in_progress',
    rawInput: p.input,
    rawOutput: undefined,
  };
}

/** `session.next.tool.success` → a completed tool snapshot (text content joined). */
export function toolSuccessSnapshot(p: { callID: string; content?: ReadonlyArray<unknown> | null }): AcpToolSnapshot {
  const output = p.content?.map((c) => (c && typeof c === 'object' && 'text' in c ? (c as { text: string }).text : '')).join('') ?? '';
  return {
    toolCallId: p.callID,
    title: p.callID,
    kind: null,
    status: 'completed',
    rawInput: undefined,
    rawOutput: output,
  };
}

/** `session.next.tool.failed` → a failed tool snapshot (error stringified). */
export function toolFailedSnapshot(p: { callID: string; error: unknown }): AcpToolSnapshot {
  return {
    toolCallId: p.callID,
    title: p.callID,
    kind: null,
    status: 'failed',
    rawInput: undefined,
    rawOutput: errToString(p.error),
  };
}

// ─── message.part.* dedup gate ────────────────────────────────────────────────

/**
 * `message.part.delta`: mark the part as streamed (so a later `message.part.updated`
 * for the same part is deduped) and return the AgentEvent to emit, or null when the
 * field is neither reasoning nor text, or a text delta strips down to empty. Mutates
 * `st.streamedPartKeys` exactly as the original inline arm did (the key is recorded
 * for text even when the cleaned delta is empty).
 */
export function classifyPartDelta(
  p: { partID: string; field?: string; delta: string },
  st: DedupState,
): AgentEvent | null {
  const isReasoning = p.field === 'reasoning' || st.partTypeById.get(p.partID) === 'reasoning';
  if (isReasoning) {
    st.streamedPartKeys.add(`reasoning:${p.partID}`);
    return { type: 'reasoning', text: p.delta };
  }
  if (p.field === 'text') {
    st.streamedPartKeys.add(`text:${p.partID}`);
    const cleaned = stripDcpTags(p.delta);
    return cleaned ? { type: 'text', text: cleaned } : null;
  }
  return null;
}

/**
 * `message.part.updated` terminal part: the dedup gate for text/reasoning (drop a
 * part already streamed via deltas; otherwise emit the finished text) plus the
 * tool-part → tool_call/tool_update mapping. Returns null when nothing should be
 * emitted. Mutates `st.partTypeById` / `st.streamedPartKeys` like the original.
 */
export function classifyUpdatedPart(part: Part, st: DedupState): AgentEvent | null {
  if (part.type === 'text' || part.type === 'reasoning') {
    st.partTypeById.set(part.id, part.type);
    const key = resolvePartDedupeKey(part, part.type);
    if (key && st.streamedPartKeys.delete(key)) return null; // already streamed via delta
    const raw = part.text ?? '';
    const text = part.type === 'text' ? stripDcpTags(raw) : raw;
    if (text && part.time?.end != null) {
      return { type: part.type, text };
    }
    return null;
  }

  if (part.type === 'tool') {
    const snap = toolPartToSnapshot(part);
    const status = part.state?.status;
    // tool_call on start (pending/running), tool_update on terminal (completed/error).
    // The current ACP path merges both into one frame; the contract keeps them
    // distinct because opencode's SSE distinguishes start from result.
    return status === 'completed' || status === 'error'
      ? { type: 'tool_update', toolCall: snap }
      : { type: 'tool_call', toolCall: snap };
  }
  // NOTE: opencode's SSE payload union carries no available-commands event, so the
  // AgentEvent 'commands' arm is intentionally never emitted here.
  return null;
}

// ─── shared error formatters (pure) ───────────────────────────────────────────

export function errMsg(e: unknown): string {
  return e instanceof Error ? e.message : String(e);
}

export function errToString(e: unknown): string {
  if (e == null) return 'unknown error';
  if (typeof e === 'string') return e;
  if (e instanceof Error) return e.message;
  try {
    return JSON.stringify(e);
  } catch {
    return String(e);
  }
}