import { type KeyboardEvent, useEffect, useRef, useState } from 'react';
import { AlertCircle, ArrowUp, Bot, ChevronDown, Circle, GitBranch, Loader2, Sparkles, User } from 'lucide-react';

import { MarkdownContent } from '@renderer/components/MarkdownContent';
import { getAssistantMessagePhase } from '@renderer/lib/messagePhase';
import { ProviderIcon } from '@renderer/components/ProviderIcons';
import {
  findModel,
  getSupportedReasoningEfforts,
  inferProvider,
  providerMeta,
  resolveReasoningEffort,
  type ModelDefinition,
} from '@shared/domain/models';
import { reasoningEffortOptions, type PatternDefinition, type ReasoningEffort } from '@shared/domain/pattern';
import { isScratchpadProject, type ProjectRecord } from '@shared/domain/project';
import type { SessionRecord } from '@shared/domain/session';

function ThinkingDots() {
  return (
    <div className="flex items-center gap-1.5">
      <span className="thinking-dot size-2 rounded-full bg-zinc-500" />
      <span className="thinking-dot size-2 rounded-full bg-zinc-500" />
      <span className="thinking-dot size-2 rounded-full bg-zinc-500" />
    </div>
  );
}

/* ── Tier badge for model dropdown ─────────────────────────── */

function TierBadge({ tier }: { tier: ModelDefinition['tier'] }) {
  if (!tier) return null;
  const styles = {
    premium: 'bg-amber-500/10 text-amber-400',
    standard: 'bg-zinc-700/50 text-zinc-500',
    fast: 'bg-emerald-500/10 text-emerald-400',
  };
  return (
    <span className={`ml-auto rounded px-1.5 py-0.5 text-[9px] font-medium ${styles[tier]}`}>
      {tier}
    </span>
  );
}

/* ── Inline model pill with dropdown ───────────────────────── */

function InlineModelPill({
  value,
  models,
  onChange,
  disabled,
}: {
  value: string;
  models: ReadonlyArray<ModelDefinition>;
  onChange: (model: string) => void;
  disabled: boolean;
}) {
  const [open, setOpen] = useState(false);
  const ref = useRef<HTMLDivElement>(null);

  useEffect(() => {
    if (!open) return;
    function handleClick(e: MouseEvent) {
      if (ref.current && !ref.current.contains(e.target as Node)) setOpen(false);
    }
    document.addEventListener('mousedown', handleClick);
    return () => document.removeEventListener('mousedown', handleClick);
  }, [open]);

  const selected = findModel(value, models);
  const provider = selected?.provider ?? inferProvider(value);
  const displayName = selected?.name ?? value ?? 'Model';

  const groupedModels = providerMeta
    .map((pg) => ({ ...pg, models: models.filter((m) => m.provider === pg.id) }))
    .filter((pg) => pg.models.length > 0);
  const otherModels = models.filter((m) => !m.provider);

  return (
    <div className="relative" ref={ref}>
      <button
        className={`inline-flex items-center gap-1.5 rounded-md border px-2 py-1 text-[12px] font-medium transition ${
          open
            ? 'border-indigo-500/40 bg-indigo-500/10 text-indigo-300'
            : 'border-zinc-700/60 bg-zinc-800/40 text-zinc-400 hover:border-zinc-600 hover:text-zinc-300'
        } disabled:cursor-not-allowed disabled:opacity-50`}
        disabled={disabled}
        onClick={() => setOpen(!open)}
        type="button"
      >
        {provider && <ProviderIcon provider={provider} className="size-3" />}
        <span className="max-w-[140px] truncate">{displayName}</span>
        <ChevronDown className={`size-3 transition ${open ? 'rotate-180' : ''}`} />
      </button>

      {open && !disabled && (
        <div className="absolute bottom-full left-0 z-40 mb-1.5 max-h-72 w-64 overflow-y-auto rounded-lg border border-zinc-700 bg-zinc-900 py-1 shadow-2xl">
          {groupedModels.map((pg) => (
            <div key={pg.id}>
              <div className="flex items-center gap-2 px-3 pb-1 pt-2.5">
                <ProviderIcon provider={pg.id} className="size-3.5" />
                <span className="text-[10px] font-semibold uppercase tracking-wider text-zinc-500">
                  {pg.label}
                </span>
              </div>
              {pg.models.map((model) => (
                <button
                  className={`flex w-full items-center gap-2 px-3 py-1.5 text-left text-[13px] transition hover:bg-zinc-800 ${
                    model.id === value ? 'bg-indigo-500/10 text-indigo-200' : 'text-zinc-300'
                  }`}
                  key={model.id}
                  onClick={() => { onChange(model.id); setOpen(false); }}
                  type="button"
                >
                  <span className="flex-1">{model.name}</span>
                  <TierBadge tier={model.tier} />
                </button>
              ))}
            </div>
          ))}
          {otherModels.length > 0 && (
            <div>
              <div className="px-3 pb-1 pt-2.5 text-[10px] font-semibold uppercase tracking-wider text-zinc-500">
                Other
              </div>
              {otherModels.map((model) => (
                <button
                  className={`flex w-full items-center gap-2 px-3 py-1.5 text-left text-[13px] transition hover:bg-zinc-800 ${
                    model.id === value ? 'bg-indigo-500/10 text-indigo-200' : 'text-zinc-300'
                  }`}
                  key={model.id}
                  onClick={() => { onChange(model.id); setOpen(false); }}
                  type="button"
                >
                  <span className="flex-1">{model.name}</span>
                  <TierBadge tier={model.tier} />
                </button>
              ))}
            </div>
          )}
        </div>
      )}
    </div>
  );
}

/* ── Inline thinking effort pill with dropdown ─────────────── */

function InlineThinkingPill({
  value,
  supportedEfforts,
  onChange,
  disabled,
}: {
  value?: ReasoningEffort;
  supportedEfforts?: ReadonlyArray<ReasoningEffort>;
  onChange: (effort: ReasoningEffort) => void;
  disabled: boolean;
}) {
  const [open, setOpen] = useState(false);
  const ref = useRef<HTMLDivElement>(null);

  useEffect(() => {
    if (!open) return;
    function handleClick(e: MouseEvent) {
      if (ref.current && !ref.current.contains(e.target as Node)) setOpen(false);
    }
    document.addEventListener('mousedown', handleClick);
    return () => document.removeEventListener('mousedown', handleClick);
  }, [open]);

  const options = supportedEfforts
    ? reasoningEffortOptions.filter((o) => supportedEfforts.includes(o.value))
    : [...reasoningEffortOptions];

  if (supportedEfforts && supportedEfforts.length === 0) {
    return (
      <span className="inline-flex items-center gap-1.5 rounded-md border border-zinc-800/40 bg-zinc-800/20 px-2 py-1 text-[12px] text-zinc-600">
        <Sparkles className="size-3" />
        N/A
      </span>
    );
  }

  const currentLabel = options.find((o) => o.value === value)?.label ?? value ?? 'Thinking';

  return (
    <div className="relative" ref={ref}>
      <button
        className={`inline-flex items-center gap-1.5 rounded-md border px-2 py-1 text-[12px] font-medium transition ${
          open
            ? 'border-indigo-500/40 bg-indigo-500/10 text-indigo-300'
            : 'border-zinc-700/60 bg-zinc-800/40 text-zinc-400 hover:border-zinc-600 hover:text-zinc-300'
        } disabled:cursor-not-allowed disabled:opacity-50`}
        disabled={disabled}
        onClick={() => setOpen(!open)}
        type="button"
      >
        <Sparkles className="size-3" />
        <span>{currentLabel}</span>
        <ChevronDown className={`size-3 transition ${open ? 'rotate-180' : ''}`} />
      </button>

      {open && !disabled && (
        <div className="absolute bottom-full left-0 z-40 mb-1.5 w-36 overflow-hidden rounded-lg border border-zinc-700 bg-zinc-900 py-1 shadow-2xl">
          {options.map((option) => (
            <button
              className={`flex w-full items-center gap-2 px-3 py-1.5 text-left text-[13px] transition hover:bg-zinc-800 ${
                option.value === value ? 'bg-indigo-500/10 text-indigo-200' : 'text-zinc-300'
              }`}
              key={option.value}
              onClick={() => { onChange(option.value); setOpen(false); }}
              type="button"
            >
              {option.label}
            </button>
          ))}
        </div>
      )}
    </div>
  );
}

/* ── ChatPane ──────────────────────────────────────────────── */

interface ChatPaneProps {
  project: ProjectRecord;
  pattern: PatternDefinition;
  session: SessionRecord;
  availableModels: ReadonlyArray<ModelDefinition>;
  onSend: (content: string) => Promise<void>;
  onUpdateScratchpadConfig?: (config: {
    model: string;
    reasoningEffort?: ReasoningEffort;
  }) => Promise<unknown>;
}

export function ChatPane({
  project,
  pattern,
  session,
  availableModels,
  onSend,
  onUpdateScratchpadConfig,
}: ChatPaneProps) {
  const [input, setInput] = useState('');
  const [configError, setConfigError] = useState<string>();
  const [isUpdatingScratchpadConfig, setIsUpdatingScratchpadConfig] = useState(false);
  const transcriptRef = useRef<HTMLDivElement>(null);
  const textareaRef = useRef<HTMLTextAreaElement>(null);

  const isSessionBusy = session.status === 'running';
  const isScratchpad = isScratchpadProject(project);
  const primaryAgent = pattern.agents[0];
  const selectedModel = primaryAgent ? findModel(primaryAgent.model, availableModels) : undefined;
  const supportedEfforts = getSupportedReasoningEfforts(selectedModel);
  const scratchpadReasoningEffort = resolveReasoningEffort(selectedModel, primaryAgent?.reasoningEffort);
  const isComposerDisabled = isSessionBusy || isUpdatingScratchpadConfig;

  useEffect(() => {
    transcriptRef.current?.scrollTo({
      top: transcriptRef.current.scrollHeight,
      behavior: 'smooth',
    });
  }, [session.messages.length, isSessionBusy]);

  useEffect(() => {
    setConfigError(undefined);
    setIsUpdatingScratchpadConfig(false);
  }, [session.id]);

  async function handleSubmit() {
    const text = input.trim();
    if (!text || isComposerDisabled) return;
    setInput('');
    await onSend(text);
  }

  async function handleScratchpadConfigChange(config: {
    model: string;
    reasoningEffort?: ReasoningEffort;
  }) {
    if (!isScratchpad || !primaryAgent || isComposerDisabled || !onUpdateScratchpadConfig) {
      return;
    }

    if (
      config.model === primaryAgent.model &&
      config.reasoningEffort === scratchpadReasoningEffort
    ) {
      return;
    }

    setConfigError(undefined);
    setIsUpdatingScratchpadConfig(true);

    try {
      await onUpdateScratchpadConfig(config);
    } catch (error) {
      setConfigError(error instanceof Error ? error.message : String(error));
    } finally {
      setIsUpdatingScratchpadConfig(false);
    }
  }

  function handleKeyDown(event: KeyboardEvent<HTMLTextAreaElement>) {
    if (event.key === 'Enter' && !event.shiftKey) {
      event.preventDefault();
      void handleSubmit();
    }
  }

  return (
    <div className="flex h-full flex-col">
      {/* Header — extra top padding clears the title bar overlay zone */}
      <header className="drag-region border-b border-[var(--color-border)] px-6 pb-3 pt-3">
        <div className="flex min-h-8 items-center justify-between">
          <div className="min-w-0">
            <h2 className="truncate text-[13px] font-semibold leading-tight text-zinc-100">{session.title}</h2>
            <p className="truncate text-[11px] leading-tight text-zinc-500">
              {isScratchpad
                ? `Scratchpad · ${pattern.name}`
                : `${project.name} · ${pattern.name} · ${pattern.mode}`}
              {!isScratchpad && project.git?.status === 'ready' && (
                <span className="ml-2 inline-flex items-center gap-1 text-zinc-600">
                  <GitBranch className="inline size-2.5" />
                  {project.git.branch ?? project.git.head?.shortHash ?? 'HEAD'}
                  {project.git.isDirty && (
                    <Circle className="inline size-1.5 fill-amber-500 text-amber-500" />
                  )}
                  {(project.git.ahead ?? 0) > 0 && <span>↑{project.git.ahead}</span>}
                  {(project.git.behind ?? 0) > 0 && <span>↓{project.git.behind}</span>}
                </span>
              )}
            </p>
          </div>
          <div className="flex items-center gap-2">
            {isSessionBusy && <span className="size-2 animate-pulse rounded-full bg-blue-400" />}
            {session.status === 'error' && (
              <div className="flex items-center gap-1.5 text-[12px] text-red-400">
                <AlertCircle className="size-3.5" />
                Error
              </div>
            )}
            {session.status === 'idle' && session.messages.length > 0 && (
              <span className="text-[12px] text-zinc-600">
                {session.messages.length} message{session.messages.length === 1 ? '' : 's'}
              </span>
            )}
          </div>
        </div>
      </header>

      {/* Messages */}
      <div className="flex-1 overflow-y-auto" ref={transcriptRef}>
        {session.messages.length === 0 ? (
          <div className="flex h-full flex-col items-center justify-center gap-2 px-6 text-center">
            <Bot className="size-10 text-zinc-800" />
            <p className="text-[13px] text-zinc-500">Send a message to start the conversation</p>
            <p className="text-[12px] text-zinc-700">
              {isScratchpad ? (
                <>
                  Scratchpad is ready for ad-hoc questions using{' '}
                  <span className="text-zinc-500">{pattern.name}</span>
                </>
              ) : (
                <>
                  Using <span className="text-zinc-500">{pattern.name}</span> in{' '}
                  <span className="text-zinc-500">{project.name}</span>
                </>
              )}
            </p>
          </div>
        ) : (
          <div className="mx-auto max-w-3xl px-6 py-4">
            <div className="space-y-1">
              {session.messages.map((message, index) => {
                const isUser = message.role === 'user';
                const phase = getAssistantMessagePhase(session, message, index);
                const assistantContainerClass =
                  phase === 'thinking'
                    ? 'border-sky-500/20 bg-sky-500/5'
                    : phase === 'final'
                      ? 'border-emerald-500/20 bg-emerald-500/5'
                      : 'border-zinc-800 bg-zinc-900/40';
                const assistantBadgeClass =
                  phase === 'thinking'
                    ? 'border-sky-400/20 bg-sky-400/10 text-sky-300'
                    : 'border-emerald-400/20 bg-emerald-400/10 text-emerald-300';
                const phaseLabel =
                  phase === 'thinking' ? 'Thinking' : phase === 'final' ? 'Final' : undefined;

                return (
                  <div className="group py-3" data-message-id={message.id} key={message.id}>
                    <div className="flex gap-3">
                      <div
                        className={`mt-0.5 flex size-7 shrink-0 items-center justify-center rounded-full ${
                          isUser ? 'bg-indigo-600 text-white' : 'bg-zinc-800 text-zinc-400'
                        }`}
                      >
                        {isUser ? <User className="size-3.5" /> : <Bot className="size-3.5" />}
                      </div>
                      <div className="min-w-0 flex-1">
                        <div className="mb-1 flex items-center gap-2 text-[12px] font-medium text-zinc-400">
                          <span>{message.authorName}</span>
                          {!isUser && phaseLabel && (
                            <span
                              className={`inline-flex items-center rounded-full border px-2 py-0.5 text-[10px] font-semibold uppercase tracking-[0.08em] ${assistantBadgeClass}`}
                            >
                              {phaseLabel}
                            </span>
                          )}
                        </div>
                        <div
                          className={
                            isUser
                              ? 'text-[14px] leading-relaxed text-zinc-200'
                              : `rounded-xl border px-4 py-3 text-[14px] leading-relaxed text-zinc-200 ${assistantContainerClass}`
                          }
                        >
                          {!isUser && message.pending ? (
                            <div className="whitespace-pre-wrap break-words text-[14px] leading-relaxed text-zinc-200">
                              {message.content}
                            </div>
                          ) : (
                            <MarkdownContent content={message.content} />
                          )}
                          {message.pending && message.content && (
                            <span className="mt-1 inline-block h-4 w-[2px] animate-pulse rounded-sm bg-zinc-400" />
                          )}
                        </div>
                        {message.pending && !message.content && <ThinkingDots />}
                      </div>
                    </div>
                  </div>
                );
              })}
            </div>
          </div>
        )}
      </div>

      {/* Input area */}
      <div className="border-t border-[var(--color-border)] px-6 py-4">
        {session.lastError && (
          <div className="mb-3 flex items-start gap-2 rounded-lg bg-red-500/10 px-3 py-2 text-[13px] text-red-300">
            <AlertCircle className="mt-0.5 size-4 shrink-0 text-red-400" />
            <span>{session.lastError}</span>
          </div>
        )}

        {configError && (
          <div className="mb-3 flex items-start gap-2 rounded-lg bg-red-500/10 px-3 py-2 text-[13px] text-red-300">
            <AlertCircle className="mt-0.5 size-4 shrink-0 text-red-400" />
            <span>{configError}</span>
          </div>
        )}

        <div className="mx-auto max-w-3xl">
          {/* Scratchpad config pills — inline above composer */}
          {isScratchpad && primaryAgent && (
            <div className="mb-2 flex items-center gap-2">
              <InlineModelPill
                disabled={isComposerDisabled}
                models={availableModels}
                onChange={(modelId) => {
                  const nextModel = findModel(modelId, availableModels);
                  void handleScratchpadConfigChange({
                    model: modelId,
                    reasoningEffort: resolveReasoningEffort(nextModel, scratchpadReasoningEffort),
                  });
                }}
                value={primaryAgent.model}
              />
              <InlineThinkingPill
                disabled={isComposerDisabled}
                onChange={(reasoningEffort) =>
                  void handleScratchpadConfigChange({
                    model: primaryAgent.model,
                    reasoningEffort,
                  })
                }
                supportedEfforts={supportedEfforts}
                value={scratchpadReasoningEffort}
              />
              {isUpdatingScratchpadConfig && (
                <Loader2 className="size-3 animate-spin text-zinc-500" />
              )}
            </div>
          )}

          <div className="relative rounded-xl border border-zinc-700 bg-zinc-900 transition-colors focus-within:border-indigo-500/50">
            <textarea
              className="auto-resize-textarea block w-full resize-none bg-transparent px-4 py-3 pr-12 text-[14px] text-zinc-100 placeholder-zinc-600 outline-none"
              disabled={isComposerDisabled}
              onChange={(event) => setInput(event.target.value)}
              onKeyDown={handleKeyDown}
              placeholder={
                isSessionBusy
                  ? 'Waiting for response...'
                  : isUpdatingScratchpadConfig
                    ? 'Saving scratchpad settings...'
                    : 'Message...'
              }
              ref={textareaRef}
              rows={1}
              value={input}
            />
            <button
              className={`absolute bottom-2 right-2 flex size-8 items-center justify-center rounded-lg transition ${
                input.trim() && !isComposerDisabled
                  ? 'bg-indigo-600 text-white hover:bg-indigo-500'
                  : 'bg-zinc-800 text-zinc-600'
              }`}
              disabled={isComposerDisabled || !input.trim()}
              onClick={() => void handleSubmit()}
              type="button"
            >
              {isSessionBusy ? (
                <Loader2 className="size-4 animate-spin" />
              ) : (
                <ArrowUp className="size-4" />
              )}
            </button>
          </div>
        </div>
      </div>
    </div>
  );
}