import { html, useState, useRef, useCallback, useMemo, useEffect } from '../lib/preact.js';
import { getStatusMeta } from '../utils/status.js';

export function SimpleInput({ sessionId, status, onRespond, autocompleteConfig = null }) {
  const [text, setText] = useState('');
  const [focused, setFocused] = useState(false);
  const [sending, setSending] = useState(false);
  const [error, setError] = useState(null);
  const [triggerInfo, setTriggerInfo] = useState(null);
  const [showAutocomplete, setShowAutocomplete] = useState(false);
  const [selectedIndex, setSelectedIndex] = useState(0);
  const textareaRef = useRef(null);
  const autocompleteRef = useRef(null);
  const meta = getStatusMeta(status);

  // Detect if cursor is at a trigger position for autocomplete
  const getTriggerInfo = useCallback((value, cursorPos) => {
    // No config means no autocomplete
    if (!autocompleteConfig) return null;

    const { trigger } = autocompleteConfig;

    // Find the start of the current "word" (after last whitespace before cursor)
    let wordStart = cursorPos;
    while (wordStart > 0 && !/\s/.test(value[wordStart - 1])) {
      wordStart--;
    }

    // Check if word starts with this agent's trigger character
    if (value[wordStart] === trigger) {
      return {
        trigger,
        filterText: value.slice(wordStart + 1, cursorPos).toLowerCase(),
        replaceStart: wordStart,
        replaceEnd: cursorPos,
      };
    }

    return null;
  }, [autocompleteConfig]);

  // Filter skills based on user input after trigger
  const filteredSkills = useMemo(() => {
    if (!autocompleteConfig || !triggerInfo) return [];

    const { skills } = autocompleteConfig;
    const { filterText } = triggerInfo;

    let filtered = skills;
    if (filterText) {
      filtered = skills.filter(s =>
        s.name.toLowerCase().includes(filterText)
      );
    }

    // Server pre-sorts, but re-sort after filtering for stability
    return filtered.sort((a, b) => a.name.localeCompare(b.name));
  }, [autocompleteConfig, triggerInfo]);

  // Show/hide autocomplete based on trigger detection
  useEffect(() => {
    const shouldShow = triggerInfo !== null;
    setShowAutocomplete(shouldShow);
    // Reset selection when dropdown opens
    if (shouldShow) {
      setSelectedIndex(0);
    }
  }, [triggerInfo]);

  // Clamp selectedIndex when filtered list changes
  useEffect(() => {
    if (filteredSkills.length > 0 && selectedIndex >= filteredSkills.length) {
      setSelectedIndex(filteredSkills.length - 1);
    }
  }, [filteredSkills.length, selectedIndex]);

  // Insert a selected skill into the text
  const insertSkill = useCallback((skill) => {
    if (!triggerInfo || !autocompleteConfig) return;

    const { trigger } = autocompleteConfig;
    const { replaceStart, replaceEnd } = triggerInfo;

    const before = text.slice(0, replaceStart);
    const after = text.slice(replaceEnd);
    const inserted = `${trigger}${skill.name} `;

    setText(before + inserted + after);
    setShowAutocomplete(false);
    setTriggerInfo(null);

    // Move cursor after inserted text
    const newCursorPos = replaceStart + inserted.length;
    setTimeout(() => {
      if (textareaRef.current) {
        textareaRef.current.selectionStart = newCursorPos;
        textareaRef.current.selectionEnd = newCursorPos;
        textareaRef.current.focus();
      }
    }, 0);
  }, [text, triggerInfo, autocompleteConfig]);

  const handleSubmit = async (e) => {
    e.preventDefault();
    e.stopPropagation();
    if (text.trim() && !sending) {
      setSending(true);
      setError(null);
      try {
        await onRespond(sessionId, text.trim(), true, 0);
        setText('');
      } catch (err) {
        setError('Failed to send message');
        console.error('SimpleInput send error:', err);
      } finally {
        setSending(false);
        // Refocus the textarea after submission
        // Use setTimeout to ensure React has re-rendered with disabled=false
        setTimeout(() => {
          textareaRef.current?.focus();
        }, 0);
      }
    }
  };

  return html`
    <form onSubmit=${handleSubmit} class="flex flex-col gap-2" onClick=${(e) => e.stopPropagation()}>
      ${error && html`
        <div class="rounded-lg border border-attention/40 bg-attention/12 px-3 py-1.5 text-sm text-attention">
          ${error}
        </div>
      `}
      <div class="flex items-end gap-2.5">
      <div class="relative flex-1">
      <textarea
        ref=${textareaRef}
        value=${text}
        onInput=${(e) => {
          const value = e.target.value;
          const cursorPos = e.target.selectionStart;
          setText(value);
          setTriggerInfo(getTriggerInfo(value, cursorPos));
          e.target.style.height = 'auto';
          e.target.style.height = e.target.scrollHeight + 'px';
        }}
        onKeyDown=${(e) => {
          if (showAutocomplete) {
            // Escape dismisses dropdown
            if (e.key === 'Escape') {
              e.preventDefault();
              setShowAutocomplete(false);
              return;
            }

            // Enter/Tab: select if matches exist, otherwise dismiss
            if (e.key === 'Enter' || e.key === 'Tab') {
              e.preventDefault();
              if (filteredSkills.length > 0 && filteredSkills[selectedIndex]) {
                insertSkill(filteredSkills[selectedIndex]);
              } else {
                setShowAutocomplete(false);
              }
              return;
            }

            // Arrow navigation
            if (filteredSkills.length > 0) {
              if (e.key === 'ArrowDown') {
                e.preventDefault();
                setSelectedIndex(i => Math.min(i + 1, filteredSkills.length - 1));
                return;
              }
              if (e.key === 'ArrowUp') {
                e.preventDefault();
                setSelectedIndex(i => Math.max(i - 1, 0));
                return;
              }
            }
          }

          // Normal Enter-to-submit (only when dropdown is closed)
          if (e.key === 'Enter' && !e.shiftKey) {
            e.preventDefault();
            handleSubmit(e);
          }
        }}
        onFocus=${() => setFocused(true)}
        onBlur=${() => setFocused(false)}
        placeholder="Send a message..."
        rows="1"
        class="w-full resize-none overflow-hidden rounded-xl border border-selection/75 bg-bg/70 px-3 py-2 text-sm text-fg transition-colors duration-150 placeholder:text-dim focus:outline-none"
        style=${{ minHeight: '38px', maxHeight: '150px', borderColor: focused ? meta.borderColor : undefined }}
        disabled=${sending}
      />
      ${showAutocomplete && html`
        <div
          ref=${autocompleteRef}
          class="absolute left-0 bottom-full mb-1 w-full max-h-48 overflow-y-auto rounded-lg border border-selection/75 bg-surface shadow-lg z-50"
        >
          ${autocompleteConfig.skills.length === 0 ? html`
            <div class="px-3 py-2 text-sm text-dim">No skills available</div>
          ` : filteredSkills.length === 0 ? html`
            <div class="px-3 py-2 text-sm text-dim">No matching skills</div>
          ` : filteredSkills.map((skill, i) => html`
            <div
              key=${i}
              class="px-3 py-2 cursor-pointer text-sm transition-colors ${
                i === selectedIndex
                  ? 'bg-selection/50 text-bright'
                  : 'text-fg hover:bg-selection/25'
              }"
              onClick=${() => insertSkill(skill)}
              onMouseEnter=${() => setSelectedIndex(i)}
            >
              <div class="font-medium font-mono text-bright">
                ${autocompleteConfig.trigger}${skill.name}
              </div>
              <div class="text-micro text-dim truncate">${skill.description}</div>
            </div>
          `)}
        </div>
      `}
      </div>
      <button
        type="submit"
        class="shrink-0 rounded-xl px-3 py-2 text-sm font-medium transition-[transform,filter] duration-150 hover:-translate-y-0.5 hover:brightness-110 disabled:cursor-not-allowed disabled:opacity-50"
        style=${{ backgroundColor: meta.borderColor, color: '#0a0f18' }}
        disabled=${sending || !text.trim()}
      >
        ${sending ? 'Sending...' : 'Send'}
      </button>
      </div>
    </form>
  `;
}