import { memo, type ReactElement } from 'react';
import type {
  ACPToolCall,
  Message,
  PermissionRequest,
  TodoItem,
} from '../adapters/types';
import type { WebShellAssistantTurnFooterRenderInfo } from '../customization';
import { useI18n } from '../i18n';
import { ErrorBoundary } from './ErrorBoundary';
import { MessageTimestamp } from './MessageTimestamp';
import { UserMessage } from './messages/UserMessage';
import {
  AssistantMessage,
  ThinkingMessage,
  type SessionContentGenerator,
} from './messages/AssistantMessage';
import { SystemMessage } from './messages/SystemMessage';
import { ToolGroup } from './messages/ToolGroup';
import { PlanMessage } from './messages/PlanMessage';
import { BtwMessage } from './messages/BtwMessage';
import { UserShellMessage } from './messages/UserShellMessage';
import { InsightProgress } from './InsightProgress';
import { InsightReady } from './InsightReady';

interface MessageItemProps {
  message: Message;
  pendingApproval?: PermissionRequest | null;
  /** Run /context detail, exactly like typing it (context-usage panels). */
  onShowContextDetail?: () => void;
  workspaceCwd?: string;
  isLatest?: boolean;
  showRetryHint?: boolean;
  onRetryClick?: () => void;
  onBranchSession?: () => void;
  showAssistantActions?: boolean;
  showAssistantBranch?: boolean;
  isLocateFlashing?: boolean;
  assistantTurnFooterInfo?: WebShellAssistantTurnFooterRenderInfo;
  generateContent?: SessionContentGenerator;
}

export const MessageItem = memo(function MessageItem({
  message,
  pendingApproval,
  onShowContextDetail,
  workspaceCwd,
  isLatest = false,
  showRetryHint = false,
  onRetryClick,
  onBranchSession,
  showAssistantActions = false,
  showAssistantBranch = false,
  isLocateFlashing = false,
  assistantTurnFooterInfo,
  generateContent,
}: MessageItemProps) {
  const { t } = useI18n();
  const body = ((): ReactElement | null => {
    switch (message.role) {
      case 'user':
        return (
          <UserMessage
            content={message.content}
            images={message.images}
            inputAnnotations={message.inputAnnotations}
            isLocateFlashing={isLocateFlashing}
          />
        );
      case 'assistant':
        return (
          <AssistantMessage
            content={message.content}
            isStreaming={message.isStreaming}
            timestamp={message.timestamp}
            onBranchSession={onBranchSession}
            showFooterActions={showAssistantActions}
            showBranchAction={showAssistantBranch}
            isLocateFlashing={isLocateFlashing}
            customFooterInfo={assistantTurnFooterInfo}
          />
        );
      case 'thinking':
        return (
          <ThinkingMessage
            messageId={message.id}
            content={message.content}
            isStreaming={message.isStreaming}
            timestamp={message.timestamp}
            isLocateFlashing={isLocateFlashing}
            generateContent={generateContent}
          />
        );
      case 'tool_group':
        return (
          <ToolGroup
            tools={message.tools}
            pendingApproval={pendingApproval}
            workspaceCwd={workspaceCwd}
            isLocateFlashing={isLocateFlashing}
          />
        );
      case 'plan':
        return (
          <PlanMessage
            id={message.id}
            todos={message.todos}
            isLocateFlashing={isLocateFlashing}
          />
        );
      case 'system':
        return (
          <SystemMessage
            content={message.content}
            variant={message.variant}
            source={message.source}
            data={message.data}
            onShowContextDetail={onShowContextDetail}
            isLatest={isLatest}
            showRetryHint={showRetryHint && message.retryable === true}
            onRetryClick={onRetryClick}
          />
        );
      case 'user_shell':
        return (
          <UserShellMessage command={message.command} output={message.output} />
        );
      case 'btw':
        return (
          <BtwMessage
            question={message.question}
            answer={message.answer}
            isPending={message.isPending}
          />
        );
      case 'insight_progress':
        return (
          <InsightProgress
            progress={{
              stage: message.stage,
              progress: message.progress,
              detail: message.detail,
            }}
          />
        );
      case 'insight_ready':
        return <InsightReady path={message.path} />;
      case 'insight_error':
        return (
          <div style={{ color: 'var(--error-color, #e06c75)' }}>
            {message.error}
          </div>
        );
      default:
        return null;
    }
  })();

  if (body === null) return null;

  // Isolate each message's render: a throw in Markdown/KaTeX/Mermaid/a tool
  // panel degrades to an inline notice rather than white-screening the whole
  // (embeddable) transcript. `resetKeys={[message]}` lets a streamed/edited/
  // retried update recover on its own; a stable broken message stays on the
  // fallback without looping.
  const safeBody = (
    <ErrorBoundary
      label={`message:${message.role}`}
      resetKeys={[message]}
      fallback={
        <MessageRenderError align={message.role === 'user' ? 'end' : 'start'} />
      }
    >
      {body}
    </ErrorBoundary>
  );

  // Re-enable text selection on every message row so users can long-press /
  // drag-select reply text. The blanket `html * { user-select: none }` in
  // standalone.css disables selection on UI chrome (native-app feel); this
  // attribute opts the message subtree back in, including descendants
  // (Markdown body, code blocks, tool panels, sub-messages).
  //
  // `display: contents` keeps this wrapper out of layout: several parents
  // (e.g. MessageTimestamp's chat row) are flex containers whose items used
  // to be the message body itself. A plain div here becomes the flex item
  // instead and shrinks to its content width, squeezing user chat bubbles
  // (whose max-width: 80% then resolves against the shrunken wrapper) so
  // even short messages wrap mid-word. The user-select re-enable rule
  // matches `[data-user-selectable] *`, so the boxless wrapper does not
  // affect it.
  const selectableSafeBody = (
    <div data-user-selectable="true" style={{ display: 'contents' }}>
      {safeBody}
    </div>
  );

  if (message.role === 'assistant') {
    if (showAssistantActions) {
      return selectableSafeBody;
    }
    return (
      <MessageTimestamp timestamp={message.timestamp}>
        {selectableSafeBody}
      </MessageTimestamp>
    );
  }

  // The cancellation marker is a right-aligned, full-width turn-terminal row;
  // a hover timestamp would overlap its text, so skip the MessageTimestamp
  // wrapper. The data-user-selectable div is still applied for consistency.
  if (message.role === 'system' && message.source === 'prompt_cancelled') {
    return selectableSafeBody;
  }

  return (
    <MessageTimestamp
      timestamp={message.timestamp}
      chatMode={message.role === 'user'}
      copyText={message.role === 'user' ? message.content : undefined}
      copyTitle={t('common.copy')}
    >
      {selectableSafeBody}
    </MessageTimestamp>
  );
}, areMessageItemPropsEqual);

// Aligns with the message it replaces: user messages are right-aligned bubbles,
// so the notice sits on the right too and still reads as that user turn's prompt
// (a left-aligned notice would look like it belongs to the previous turn's
// output). Assistant and other rows are left-aligned, matching their layout.
function MessageRenderError({ align }: { align: 'start' | 'end' }) {
  const { t } = useI18n();
  return (
    <div
      role="alert"
      style={{
        display: 'flex',
        justifyContent: align === 'end' ? 'flex-end' : 'flex-start',
      }}
    >
      <span
        style={{
          color: 'var(--error-color, #e06c75)',
          fontSize: '0.85em',
          opacity: 0.85,
        }}
      >
        {t('message.renderError')}
      </span>
    </div>
  );
}

function areMessageItemPropsEqual(
  prev: MessageItemProps,
  next: MessageItemProps,
): boolean {
  if (prev.pendingApproval?.id !== next.pendingApproval?.id) return false;
  if (prev.onShowContextDetail !== next.onShowContextDetail) return false;
  if (prev.workspaceCwd !== next.workspaceCwd) return false;
  if (prev.isLatest !== next.isLatest) return false;
  if (prev.showRetryHint !== next.showRetryHint) return false;
  if (prev.onRetryClick !== next.onRetryClick) return false;
  if (prev.onBranchSession !== next.onBranchSession) return false;
  if (prev.showAssistantActions !== next.showAssistantActions) return false;
  if (prev.showAssistantBranch !== next.showAssistantBranch) return false;
  if (prev.isLocateFlashing !== next.isLocateFlashing) return false;
  if (prev.generateContent !== next.generateContent) return false;
  if (
    !areAssistantTurnFooterInfosEqual(
      prev.assistantTurnFooterInfo,
      next.assistantTurnFooterInfo,
    )
  ) {
    return false;
  }
  return areMessagesEqual(prev.message, next.message);
}

function areAssistantTurnFooterInfosEqual(
  prev?: WebShellAssistantTurnFooterRenderInfo,
  next?: WebShellAssistantTurnFooterRenderInfo,
): boolean {
  if (prev === next) return true;
  if (!prev || !next) return false;
  return (
    prev.turnId === next.turnId &&
    prev.message.id === next.message.id &&
    prev.message.content === next.message.content &&
    prev.message.isStreaming === next.message.isStreaming &&
    prev.message.timestamp === next.message.timestamp
  );
}

function areMessagesEqual(prev: Message, next: Message): boolean {
  if (prev === next) return true;
  if (prev.id !== next.id || prev.role !== next.role) return false;
  if (prev.timestamp !== next.timestamp) return false;
  switch (prev.role) {
    case 'user':
      return (
        next.role === 'user' &&
        prev.content === next.content &&
        stableImagesEqual(prev.images, next.images)
      );
    case 'assistant':
      return (
        next.role === 'assistant' &&
        prev.content === next.content &&
        prev.isStreaming === next.isStreaming
      );
    case 'thinking':
      return (
        next.role === 'thinking' &&
        prev.content === next.content &&
        prev.isStreaming === next.isStreaming
      );
    case 'system':
      return (
        next.role === 'system' &&
        prev.content === next.content &&
        prev.variant === next.variant &&
        prev.retryable === next.retryable &&
        prev.source === next.source &&
        prev.data === next.data
      );
    case 'user_shell':
      return (
        next.role === 'user_shell' &&
        prev.command === next.command &&
        prev.output === next.output &&
        prev.cwd === next.cwd
      );
    case 'btw':
      return (
        next.role === 'btw' &&
        prev.question === next.question &&
        prev.answer === next.answer &&
        prev.isPending === next.isPending
      );
    case 'insight_progress':
      return (
        next.role === 'insight_progress' &&
        prev.stage === next.stage &&
        prev.progress === next.progress &&
        prev.detail === next.detail
      );
    case 'insight_ready':
      return next.role === 'insight_ready' && prev.path === next.path;
    case 'insight_error':
      return next.role === 'insight_error' && prev.error === next.error;
    case 'plan':
      return next.role === 'plan' && areTodosEqual(prev.todos, next.todos);
    case 'tool_group':
      return (
        next.role === 'tool_group' &&
        prev.tools.length === next.tools.length &&
        prev.tools.every((tool, index) =>
          areToolCallsEqual(tool, next.tools[index]),
        )
      );
    default:
      return false;
  }
}

function areTodosEqual(prev: TodoItem[], next: TodoItem[]): boolean {
  return (
    prev.length === next.length &&
    prev.every((todo, index) => {
      const other = next[index];
      return (
        other &&
        todo.id === other.id &&
        todo.content === other.content &&
        todo.status === other.status &&
        todo.priority === other.priority
      );
    })
  );
}

function areToolCallsEqual(
  prev: ACPToolCall,
  next: ACPToolCall | undefined,
): boolean {
  if (!next) return false;
  return (
    prev.callId === next.callId &&
    prev.toolName === next.toolName &&
    prev.status === next.status &&
    prev.title === next.title &&
    prev.kind === next.kind &&
    prev.startTime === next.startTime &&
    prev.endTime === next.endTime &&
    prev.subContent === next.subContent &&
    stableJson(prev.args) === stableJson(next.args) &&
    stableJson(prev.rawOutput) === stableJson(next.rawOutput) &&
    stableJson(prev.locations) === stableJson(next.locations) &&
    stableJson(prev.content) === stableJson(next.content) &&
    areToolListsEqual(prev.subTools, next.subTools)
  );
}

function areToolListsEqual(
  prev: ACPToolCall[] | undefined,
  next: ACPToolCall[] | undefined,
): boolean {
  if (!prev && !next) return true;
  if (!prev || !next || prev.length !== next.length) return false;
  return prev.every((tool, index) => areToolCallsEqual(tool, next[index]));
}

const jsonCache = new WeakMap<object, string>();

function stableImagesEqual(
  a: Array<{ data: string; mimeType: string }> | undefined,
  b: Array<{ data: string; mimeType: string }> | undefined,
): boolean {
  if (a === b) return true;
  if (!a || !b || a.length !== b.length) return false;
  return a.every(
    (img, i) => img.data === b[i].data && img.mimeType === b[i].mimeType,
  );
}

function stableJson(value: unknown): string {
  if (value === undefined) return '';
  if (value !== null && typeof value === 'object') {
    let cached = jsonCache.get(value);
    if (cached !== undefined) return cached;
    try {
      cached = JSON.stringify(value);
    } catch {
      cached = String(value);
    }
    jsonCache.set(value, cached);
    return cached;
  }
  try {
    return JSON.stringify(value);
  } catch {
    return String(value);
  }
}