import { useMemo, useState } from 'react'
import { ApiError, declareParam, type ParamDeclaration } from '../lib/api'
import { CollapseToggle, PopOutButton, sectionHeaderClassName, sectionHeaderLeftClassName, useSectionCollapsed } from './CollapsibleSection'
import { HelpIcon } from './HelpIcon'

const EMPTY_KIND: ParamDeclaration['kind'] = 'string'

type ExtractionSource = 'regex' | 'json_field'

/// A JSON *object* (not an array/scalar) parses cleanly and pretty-prints with braces — the same
/// shape a JSON field path can be read from, so this is the "line looks like JSON" gate that
/// unlocks the "JSON field" extraction option.
function looksLikeJsonObject(text: string): boolean {
  const trimmed = text.trim()
  if (!trimmed.startsWith('{')) return false
  try {
    const parsed = JSON.parse(trimmed)
    return typeof parsed === 'object' && parsed !== null && !Array.isArray(parsed)
  } catch {
    return false
  }
}

export function Params({ params, onDeclared }: { params: ParamDeclaration[]; onDeclared: () => void }) {
  const [name, setName] = useState('')
  const [regex, setRegex] = useState('')
  const [captureGroup, setCaptureGroup] = useState('')
  const [jsonFieldPath, setJsonFieldPath] = useState('')
  const [source, setSource] = useState<ExtractionSource>('regex')
  const [kind, setKind] = useState<ParamDeclaration['kind']>(EMPTY_KIND)
  const [submitError, setSubmitError] = useState<string | null>(null)
  const [submitting, setSubmitting] = useState(false)
  const [collapsed, setCollapsed] = useSectionCollapsed('params')

  // The message match regex doubles as a sample line here so a pasted JSON log line unlocks the
  // "JSON field" extraction option — regex-based params are unaffected either way.
  const detectedJson = useMemo(() => looksLikeJsonObject(regex), [regex])
  const effectiveSource: ExtractionSource = detectedJson ? source : 'regex'

  async function handleSubmit(e: React.FormEvent) {
    e.preventDefault()
    setSubmitError(null)
    setSubmitting(true)
    try {
      await declareParam({
        name,
        message_match_regex: regex,
        capture_group: effectiveSource === 'json_field' ? '' : captureGroup,
        json_field_path: effectiveSource === 'json_field' ? jsonFieldPath : null,
        kind,
      })
      setName('')
      setRegex('')
      setCaptureGroup('')
      setJsonFieldPath('')
      setSource('regex')
      setKind(EMPTY_KIND)
      onDeclared()
    } catch (err) {
      setSubmitError(err instanceof ApiError ? err.message : 'Failed to declare param')
    } finally {
      setSubmitting(false)
    }
  }

  return (
    <div className="border-b border-border text-sm">
      <div className={sectionHeaderClassName}>
        <div className={sectionHeaderLeftClassName}>
          Params
          <HelpIcon sectionId="parameters" label="Help: Params" />
        </div>
        <div className="flex items-center gap-1.5">
          <CollapseToggle collapsed={collapsed} onToggle={() => setCollapsed(!collapsed)} />
          <PopOutButton section="params" />
        </div>
      </div>
      <div className="flex gap-4 p-3" hidden={collapsed}>
        <form onSubmit={handleSubmit} className="w-80 shrink-0 space-y-2">
          <div>
            <label className="mb-1 block text-xs text-text-subtle">Name</label>
            <input
              className="w-full rounded border border-border-soft bg-surface-1 px-2 py-1 text-sm text-text placeholder:text-text-subtle focus:border-border-strong focus:outline-none"
              value={name}
              onChange={(e) => setName(e.target.value)}
              placeholder="path"
              required
            />
          </div>
          <div>
            <label className="mb-1 block text-xs text-text-subtle">Message match regex</label>
            <input
              className="w-full rounded border border-border-soft bg-surface-1 px-2 py-1 font-mono text-sm text-text placeholder:text-text-subtle focus:border-border-strong focus:outline-none"
              value={regex}
              onChange={(e) => setRegex(e.target.value)}
              placeholder={String.raw`request path=(?P<path>\S+)`}
              required
            />
          </div>
          {detectedJson && (
            <div>
              <label className="mb-1 block text-xs text-text-subtle">Extraction</label>
              <select
                className="w-full rounded border border-border-soft bg-surface-1 px-2 py-1 text-xs text-text focus:border-border-strong focus:outline-none"
                value={source}
                onChange={(e) => setSource(e.target.value as ExtractionSource)}
              >
                <option value="regex">Regex capture group</option>
                <option value="json_field">JSON field</option>
              </select>
            </div>
          )}
          {effectiveSource === 'json_field' ? (
            <div className="flex items-end gap-1">
              <div className="min-w-0 flex-1">
                <label className="mb-1 block text-xs text-text-subtle">JSON field path</label>
                <input
                  className="w-full min-w-0 rounded border border-border-soft bg-surface-1 px-1.5 py-1 font-mono text-xs text-text placeholder:text-text-subtle focus:border-border-strong focus:outline-none"
                  value={jsonFieldPath}
                  onChange={(e) => setJsonFieldPath(e.target.value)}
                  placeholder="foo.bar"
                  required
                />
              </div>
              <select
                className="rounded border border-border-soft bg-surface-1 px-1 py-1 text-xs text-text focus:border-border-strong focus:outline-none"
                value={kind}
                onChange={(e) => setKind(e.target.value as ParamDeclaration['kind'])}
              >
                <option value="string">string</option>
                <option value="number">number</option>
                <option value="timestamp">timestamp</option>
                <option value="duration">duration</option>
              </select>
            </div>
          ) : (
            <div className="flex items-end gap-1">
              <div className="min-w-0 flex-1">
                <label className="mb-1 block text-xs text-text-subtle">Capture group</label>
                <input
                  className="w-full min-w-0 rounded border border-border-soft bg-surface-1 px-1.5 py-1 text-xs text-text placeholder:text-text-subtle focus:border-border-strong focus:outline-none"
                  value={captureGroup}
                  onChange={(e) => setCaptureGroup(e.target.value)}
                  placeholder="path"
                  required
                />
              </div>
              <select
                className="rounded border border-border-soft bg-surface-1 px-1 py-1 text-xs text-text focus:border-border-strong focus:outline-none"
                value={kind}
                onChange={(e) => setKind(e.target.value as ParamDeclaration['kind'])}
              >
                <option value="string">string</option>
                <option value="number">number</option>
                <option value="timestamp">timestamp</option>
                <option value="duration">duration</option>
              </select>
            </div>
          )}
          {submitError && <div className="rounded border border-danger-border bg-danger-bg/50 px-2 py-1 text-xs text-danger-text">{submitError}</div>}
          <button
            type="submit"
            disabled={submitting}
            className="rounded border border-border-soft px-3 py-1 text-sm text-text-secondary hover:bg-surface-2 disabled:opacity-50"
          >
            {submitting ? 'Declaring…' : 'Declare param'}
          </button>
        </form>

        <div className="min-w-0 flex-1">
          <div className="mb-1 text-xs text-text-subtle">Declared params</div>
          <div className="flex flex-wrap gap-1">
            {params.length === 0 && <span className="text-xs text-text-faint">No params declared yet.</span>}
            {params.map((p) => (
              <span
                key={p.name}
                className="rounded border border-border-soft px-2 py-1 text-xs text-text-secondary"
                title={p.message_match_regex}
              >
                {p.name} ({p.kind}, {p.json_field_path ? `json field ${p.json_field_path}` : `group ${p.capture_group}`})
              </span>
            ))}
          </div>
        </div>
      </div>
    </div>
  )
}