import { useEffect, useRef, useState, type ReactNode } from 'react'
import type { DocsTarget } from '../lib/docsNav'

/// One accordion section: a title plus its body, rendered as plain JSX so
/// each page can mix prose, lists, and inline code without pulling in a
/// markdown renderer for what is currently five static pages.
interface DocSection {
  id: string
  title: string
  body: ReactNode
}

function Code({ children }: { children: string }) {
  return <code className="rounded bg-surface-2 px-1 py-0.5 font-mono text-[11px] text-text">{children}</code>
}

const SECTIONS: DocSection[] = [
  {
    id: 'general',
    title: 'General idea',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          ottyl turns a CLI program's stdout into a Grafana-like dashboard: pipe a program's output into it, and it
          indexes each line in memory as it arrives, then serves a webapp dashboard over the same process.
        </p>
        <p>
          <Code>{'cli_command --verbose | ottyl'}</Code>
        </p>
        <p>
          Everything — ingested log lines, declared params, declared metrics, and derived buckets — lives in one
          in-memory index for the life of the process. Nothing is written to disk unless you explicitly save a{' '}
          <em>profile</em> or change a <em>setting</em>.
        </p>
        <p className="font-semibold text-text">CLI arguments</p>
        <ul className="list-disc pl-5">
          <li>
            <Code>--port</Code> — port to serve the API and webapp on (default <Code>8420</Code>).
          </li>
          <li>
            <Code>--static-dir</Code> — directory containing the built webapp (default <Code>webapp/dist</Code>).
          </li>
          <li>
            <Code>--settings-path</Code> — path to the settings file; defaults to a per-OS config location (e.g.{' '}
            <Code>~/.config/ottyl/settings.json</Code> on Linux).
          </li>
        </ul>
        <p className="font-semibold text-text">Settings</p>
        <p>
          There is exactly one <em>settings</em> file per machine, holding the colour scheme, any imported/linked CSS,
          and which profile is active. Settings "owns" profiles in that sense — it only tracks pointers (known
          profile names, which one is active); the profiles themselves (params, metrics, dashboards) are stored
          separately, next to the settings file by default.
        </p>
        <p className="font-semibold text-text">Profiles</p>
        <p>
          A profile is a named bundle of parsing/indexing rules for a particular CLI app — which params and metrics
          to derive from its log output, plus any saved dashboards — so restarting ottyl against the same program
          doesn't lose your setup. There is always a <Code>Default</Code> profile, and it can't be deleted. Creating
          a new profile copies the currently active one (or starts empty if none is active), so variations build on
          what you already have rather than starting from scratch. Switching profiles hot-swaps the running engine's
          declared params/metrics immediately, with no restart needed.
        </p>
      </div>
    ),
  },
  {
    id: 'filtering',
    title: 'Filtering',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          The filter bar above the timeline takes a syntax-aware query combining regex search over raw log text with
          comparisons against declared metrics, joined by <Code>and</Code>/<Code>or</Code>:
        </p>
        <p>
          <Code>{'regex("error") and sequence<5 or timestamp>12:00'}</Code>
        </p>
        <p>
          <Code>{'metric_name[param]<5'}</Code> compares a metric's captured param value against a number, string, or
          timestamp. <Code>sequence</Code> and <Code>timestamp</Code> are reserved metric names — every ingested log
          line has both, so they're always available to filter on without declaring anything.
        </p>
        <p className="font-semibold text-text">Date/time formats</p>
        <p>Timestamp comparisons accept several forms:</p>
        <ul className="list-disc pl-5">
          <li>
            relative, humantime-style offsets from now — <Code>5h</Code>, <Code>-3m</Code>
          </li>
          <li>absolute clock times — e.g. 12:00</li>
          <li>full dates</li>
        </ul>
        <p>
          The same filter string is sent to both <Code>GET /api/logs</Code> and <Code>GET /api/timeline</Code> as the{' '}
          <Code>filter</Code> query param and evaluated on the server; a parse error comes back from the server and
          surfaces as inline text under the filter bar rather than crashing the page.
        </p>
      </div>
    ),
  },
  {
    id: 'parameters',
    title: 'Parameters',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          A parameter declaration tells ottyl how to derive a named value from a raw log line: a regex that must
          match the message, plus a capture group within it, plus a type (<Code>string</Code>, <Code>number</Code>,
          or <Code>timestamp</Code>). Once declared, every already-ingested line gets retroactively indexed for that
          param, and every new line is checked against it as it arrives.
        </p>
        <p>
          Params are the building block metrics are made of (a metric declaration is really a message-match regex
          plus a set of param matchers), and they're also what drives filtering and the log preview's column picker —
          declaring a <Code>duration</Code> param, for instance, makes <Code>duration</Code> available as a column in
          the log table and as a comparable value in the filter bar.
        </p>
        <p>
          Declaring a param independent of a metric is supported by the API (<Code>POST /api/params</Code>), used
          today via the Metrics panel's declaration form and read back by the log preview's column picker; there
          isn't yet a standalone "declare a bare param" form in the UI.
        </p>
      </div>
    ),
  },
  {
    id: 'timeline',
    title: 'Timeline',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          The timeline above the log table renders log volume per bucket over the active window. Drag across it to
          select a fixed time range — it narrows the log table, metrics, and dashboards below to that window.
        </p>
        <p>
          The preset buttons (<Code>All</Code>, <Code>5m</Code>, <Code>15m</Code>, <Code>1h</Code>,{' '}
          <Code>24h</Code>) are Grafana-style shortcuts for the same thing: <Code>All</Code> clears the range
          entirely, and a relative preset is <em>rolling</em> — its window keeps advancing to stay "last N minutes
          from now" rather than freezing at the moment you picked it. Dragging on the timeline while a preset is
          active switches back to a fixed (non-rolling) range, same as dragging normally would.
        </p>
      </div>
    ),
  },
  {
    id: 'log-preview',
    title: 'Log preview',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          The log table lists ingested lines newest-last, each with its sequence number, timestamp, and raw text. The
          column picker (top-right) adds a column per declared param, showing that line's derived value for it (or a
          blank if it didn't match) — a quick way to eyeball params without switching to the Metrics panel.
        </p>
      </div>
    ),
  },
  {
    id: 'metrics',
    title: 'Metrics',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          Every metric is fundamentally a <em>counter</em>: a message-match regex paired with one or more named param
          matchers (each with its own capture group and type). Every log line matching the regex is one counter
          increment — a timestamped occurrence, tagged with the labels captured from that line.
        </p>
        <p>
          Each param is either a <strong>label</strong> (the default) or the metric's single <strong>value</strong>{' '}
          param. Label params identify which bucket an occurrence belongs to; a value param's captured number becomes
          that occurrence's stored value instead of a label — e.g. a <Code>duration</Code> param marked{' '}
          <em>value</em> lets you query the distribution or latest reading of durations, not just how often they
          occurred. A metric with only label params still works exactly as before: every occurrence's value defaults
          to a fixed <Code>1</Code> (a pure occurrence count).
        </p>
        <p>
          Declaring a metric backfills it against everything already ingested, then continues indexing new lines as
          they arrive — there's no need to restart ingestion or re-declare after the fact.
        </p>
        <p>
          The Metrics panel lets you declare a metric, pick one from the declared list, and see its bucket values
          grouped by label combination over the active time range — occurrence count per group, plus a small trend
          sparkline. That same data is what dashboard panels query via PromQL (see below), including two forms{' '}
          <em>derived</em> from a counter's value param rather than stored separately:
        </p>
        <ul className="list-disc pl-5">
          <li>
            <span className="font-semibold text-text">
              <Code>histogram(metric_name[width])</Code>
            </span>{' '}
            — buckets every matching event's value into fixed-width buckets of size <Code>width</Code>, e.g.{' '}
            <Code>histogram(durations[10])</Code>.
          </li>
          <li>
            <span className="font-semibold text-text">
              <Code>gauge(metric_name)</Code>
            </span>{' '}
            — the most-recent value per label combination in the active range, i.e. the counter collapsed to its
            latest reading.
          </li>
        </ul>
      </div>
    ),
  },
  {
    id: 'dashboards',
    title: 'Dashboards',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          Dashboards work like Grafana: each one is a named set of panels, and each panel is a PromQL query paired
          with a chart type — bar, line, or pie. Panels preview live as you edit the query, and a malformed query
          shows an inline error instead of breaking the page.
        </p>
        <ul className="list-disc pl-5">
          <li>
            <span className="font-semibold text-text">Line</span> — one series per label combination, time on the
            x-axis.
          </li>
          <li>
            <span className="font-semibold text-text">Bar</span> — the latest value per series (a snapshot of "where
            things are now").
          </li>
          <li>
            <span className="font-semibold text-text">Pie</span> — each series' share of the summed total across the
            active range.
          </li>
        </ul>
        <p>
          Dashboards are saved per profile, so they travel with a profile when you switch or copy it, and require an
          active profile to create or save — pick or create one from the settings menu first.
        </p>
      </div>
    ),
  },
  {
    id: 'alerts',
    title: 'Alerts',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          An alert rule fires a notification when its condition matches a newly-ingested log line — evaluated per
          line as it arrives, not backfilled against history. There are four condition types:
        </p>
        <ul className="list-disc pl-5">
          <li>
            <span className="font-semibold text-text">Immediate</span> — fires once per line matching a query.
          </li>
          <li>
            <span className="font-semibold text-text">Threshold</span> — fires when a query's match count within a
            rolling window crosses a numeric threshold.
          </li>
          <li>
            <span className="font-semibold text-text">NewValue</span> — fires the first time a field regex captures a
            value not seen before by this rule (seen values live only in memory, so a restart forgets them).
          </li>
          <li>
            <span className="font-semibold text-text">Ratio</span> — fires when the ratio of two queries' match
            counts within a rolling window crosses a numeric ratio.
          </li>
        </ul>
        <p>
          Query-based conditions (Immediate/Threshold/Ratio) reuse the filter bar's query syntax, but only the subset
          that evaluates against a single line's own fields — <Code>regex(...)</Code>, <Code>sequence</Code>,{' '}
          <Code>timestamp</Code>, and <Code>and</Code>/<Code>or</Code>. A <Code>metric_name[param]</Code> comparison
          isn't supported in an alert query.
        </p>
        <p>
          A window accepts a plain number of milliseconds or a humantime-style duration like <Code>30s</Code>,{' '}
          <Code>5m</Code>, <Code>1h</Code>.
        </p>
        <p>
          Every rule delivers to an <em>ntfy</em> sink: a topic (required) and an optional server override (defaults
          to <Code>https://ntfy.sh</Code>). "Send test notification" delivers to whatever topic/server is currently
          entered in the form, without needing to save the rule first — handy for verifying the sink before
          committing to it.
        </p>
      </div>
    ),
  },
  {
    id: 'settings',
    title: 'Settings',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          The Settings panel controls process-wide state: colour scheme, the maximum number of logs kept in memory
          (blank means unlimited), and imported/linked CSS. These apply immediately and persist to the single
          settings file on disk — no save button needed.
        </p>
      </div>
    ),
  },
  {
    id: 'presets',
    title: 'Presets',
    body: (
      <div className="flex flex-col gap-2">
        <p>
          The Presets panel manages profiles: create, switch, and delete them. Switching activates a profile's
          params/metrics in the running engine immediately, with no restart needed — see the <em>General idea</em>{' '}
          section above for what a profile stores.
        </p>
      </div>
    ),
  },
]

/** How long a flashed section stays highlighted before settling back to normal. */
const FLASH_DURATION_MS = 1200

export function DocsPanel({ target }: { target?: DocsTarget | null }) {
  const [openId, setOpenId] = useState<string | null>(SECTIONS[0].id)
  const [flashId, setFlashId] = useState<string | null>(null)
  const sectionRefs = useRef<Record<string, HTMLDivElement | null>>({})

  // Keyed on `target?.nonce` (not `target?.sectionId`) so clicking the same
  // "?" icon twice in a row re-triggers the flash rather than being a no-op
  // because the panel is already open to that section.
  useEffect(() => {
    if (!target) return
    setOpenId(target.sectionId)
    const raf = requestAnimationFrame(() => {
      sectionRefs.current[target.sectionId]?.scrollIntoView({ behavior: 'smooth', block: 'nearest' })
    })
    setFlashId(target.sectionId)
    const timeout = setTimeout(() => setFlashId(null), FLASH_DURATION_MS)
    return () => {
      cancelAnimationFrame(raf)
      clearTimeout(timeout)
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [target?.nonce])

  return (
    <div className="flex flex-col gap-1 text-sm text-text-secondary">
      {SECTIONS.map((section) => {
        const isOpen = openId === section.id
        const isFlashing = flashId === section.id
        return (
          <div
            key={section.id}
            ref={(el) => {
              sectionRefs.current[section.id] = el
            }}
            className={`rounded border transition-colors duration-500 ${
              isFlashing ? 'border-accent bg-accent-soft/25' : 'border-border'
            }`}
          >
            <button
              type="button"
              onClick={() => setOpenId(isOpen ? null : section.id)}
              className="flex w-full items-center justify-between px-3 py-2 text-left text-sm font-semibold text-text hover:bg-surface-2"
              aria-expanded={isOpen}
            >
              {section.title}
              <span className="text-text-muted">{isOpen ? '−' : '+'}</span>
            </button>
            {isOpen && <div className="border-t border-border px-3 py-3">{section.body}</div>}
          </div>
        )
      })}
    </div>
  )
}