import * as h3 from 'h3-js'
import * as turf from '@turf/turf'
import roadsRaw from '../../data/bengaluru-roads.geojson?raw'
import scoredRaw from '../../data/gridloc_scored.json?raw'
import { H3_RESOLUTION } from './h3'

// Bengaluru center.
export const BLR_LAT = 12.9716
export const BLR_LNG = 77.5946

// Real model categories from gridloc_final_scored:
//   confirmed  - certified chronic hotspot (high observed, statistically hot)
//   blind_spot - high expected demand but under-observed (likely under-enforced)
//   quirk      - certified one-off anomaly (hot, but low ongoing priority)
//   calm       - no signal
export type HexType = 'confirmed' | 'blind_spot' | 'quirk' | 'calm'

export type Hex = {
  h3: string
  observedTraffic: number // 0-100, from model O
  expectedTraffic: number // 0-100, from model E
  type: HexType
  zone: string // snapped road name (used to group the ranked list)
  center: [number, number] // [lat, lng]
  // Real model fields, surfaced in the detail panel.
  giZ: number // Getis-Ord hotspot z-score
  priority: number // 0-1 priority score (drives ranking)
  certified: boolean
  rawCount: number
  road: string
  reason: string
  timeBucket: string
  profile: Record<string, number> // priority per time bucket
}

/**
 * A road slice inside a hex, as a full-carriageway-width polygon footprint.
 * These come from OpenStreetMap geometry (for road-SHAPE rendering only) - they
 * are NOT scored by the model, so they carry no per-road severity. `name` is the
 * real OSM street name; `type` is just the parent cell's classification, used to
 * tint the drawn shape, not a per-road measurement.
 */
export type RoadSegment = {
  id: number
  hexId: string // the H3 cell this segment belongs to
  name: string // real OSM street name ('Unnamed road' if OSM had none)
  type: HexType // parent cell's category - for tinting the shape only
  widthMeters: number
  polygon: Array<[number, number]> // [lng, lat] outer ring
}

// Shape of a record in the bundled scored dataset.
type ScoredCell = {
  h3: string
  lat: number
  lng: number
  snapLat: number
  snapLng: number
  O: number
  E: number
  giZ: number
  priority: number
  category: HexType
  road: string
  certified: boolean
  rawCount: number
  timeBucket: string
  reason: string
  profile: Record<string, number>
}

/**
 * Load the real scored model output (one representative - worst time-bucket -
 * row per H3 cell). Runs ONCE at module load. Pure + deterministic (the JSON is
 * a static build artifact of gridloc_final_scored.parquet).
 */
function buildHexData(): Array<Hex> {
  const cells = JSON.parse(scoredRaw) as Array<ScoredCell>
  return cells.map((c) => ({
    h3: c.h3,
    observedTraffic: Math.round(c.O * 100),
    expectedTraffic: Math.round(c.E * 100),
    type: c.category,
    zone: c.road && c.road !== 'Unnamed Road' ? c.road : 'Unnamed stretch',
    center: [c.lat, c.lng],
    giZ: c.giZ,
    priority: c.priority,
    certified: c.certified,
    rawCount: c.rawCount,
    road: c.road,
    reason: c.reason,
    timeBucket: c.timeBucket,
    profile: c.profile ?? {},
  }))
}

/**
 * Turn a [lng,lat] polyline into a road-width polygon footprint via turf.buffer.
 * Wrapped so a malformed input logs instead of failing silently.
 */
function bufferLineToPolygon(
  line: Array<[number, number]>,
  widthMeters: number,
  id: number,
): Array<[number, number]> | null {
  try {
    const buffered = turf.buffer(turf.lineString(line), widthMeters / 2, {
      units: 'meters',
    })
    if (!buffered) {
      console.error('[twin] buffer returned null for segment', id)
      return null
    }
    const geom = buffered.geometry
    if (geom.type === 'Polygon') {
      return geom.coordinates[0] as Array<[number, number]>
    }
    if (geom.type === 'MultiPolygon') {
      return geom.coordinates[0][0] as Array<[number, number]>
    }
    console.error('[twin] unexpected buffer geometry', (geom as { type: string }).type, 'seg', id)
    return null
  } catch (err) {
    console.error('[twin] buffer failed for segment', id, err)
    return null
  }
}

type RoadFeature = {
  properties: { name: string; highway: string; widthMeters: number }
  geometry: { type: 'LineString'; coordinates: Array<[number, number]> }
}

/**
 * Derive road segments from REAL cached OSM geometry (public Overpass fetched
 * once at build time → src/data/bengaluru-roads.geojson). Runs ONCE at module
 * load. For each patrol/check hex we keep up to 5 real road slices that fall
 * inside that exact H3 cell, so segments sit ON the actual streets.
 *
 * Pipeline:
 *  1. Build the set of patrol/check cells (calm hexes get no segments).
 *  2. Prune the 11k roads to those with at least one vertex in a target cell
 *     (cheap latLngToCell test) before any expensive chunking.
 *  3. Chunk each kept road into ~250m slices with turf.lineChunk - this
 *     PRESERVES original point order along the road (no reordering/interp).
 *  4. Assign each slice to a cell via its midpoint, h3.latLngToCell(lat,lng,res)
 *     - note the (lat, lng) argument order.
 *  5. Buffer each slice to its carriageway-width polygon footprint.
 */
function generateSegments(hexes: Array<Hex>): Array<RoadSegment> {
  // Target cells = the actionable categories (everything except calm). These
  // OSM slices are drawn purely to show the road SHAPES inside a cell - they're
  // not scored, so no per-road severity is computed.
  const cellType = new Map<string, HexType>()
  for (const h of hexes) {
    if (h.type !== 'calm') cellType.set(h.h3, h.type)
  }

  const fc = JSON.parse(roadsRaw) as { features: Array<RoadFeature> }

  // Per-cell accumulator of candidate slices.
  type Slice = { coords: Array<[number, number]>; name: string; width: number }
  const byCell = new Map<string, Array<Slice>>()

  for (const feat of fc.features) {
    const coords = feat.geometry?.coordinates
    if (!Array.isArray(coords) || coords.length < 2) continue

    // Prune: does this road touch any target cell at all?
    let touches = false
    for (const [lng, lat] of coords) {
      if (cellType.has(h3.latLngToCell(lat, lng, H3_RESOLUTION))) {
        touches = true
        break
      }
    }
    if (!touches) continue

    // Chunk into ~250m order-preserving slices.
    let chunks
    try {
      chunks = turf.lineChunk(turf.lineString(coords), 0.25, {
        units: 'kilometers',
      })
    } catch {
      continue
    }

    const width = feat.properties?.widthMeters ?? 8
    const name = feat.properties?.name ?? 'Unnamed road'

    for (const chunk of chunks.features) {
      const cc = chunk.geometry.coordinates as Array<[number, number]>
      if (cc.length < 2) continue
      // Midpoint cell assignment (lat, lng order).
      const mid = cc[Math.floor(cc.length / 2)]
      const cell = h3.latLngToCell(mid[1], mid[0], H3_RESOLUTION)
      const type = cellType.get(cell)
      if (!type) continue
      const list = byCell.get(cell) ?? []
      list.push({ coords: cc, name, width })
      byCell.set(cell, list)
    }
  }

  // Emit up to 5 slices per cell as width-buffered polygons. Uniform styling -
  // these are road shapes, not measurements.
  const out: Array<RoadSegment> = []
  let id = 0
  for (const [cell, slices] of byCell) {
    const type = cellType.get(cell)!
    for (const slice of slices.slice(0, 5)) {
      const polygon = bufferLineToPolygon(slice.coords, slice.width, id)
      if (!polygon) continue
      out.push({
        id: id++,
        hexId: cell,
        name: slice.name,
        type,
        widthMeters: slice.width,
        polygon,
      })
    }
  }

  return out
}

/** Every scored H3 cell in the model output - loaded ONCE from the dataset. */
export const MOCK_HEXES: Array<Hex> = buildHexData()
// Backwards-compatible alias used elsewhere in the codebase.
export const HEXES = MOCK_HEXES

/** Real road segments for actionable hexes - generated ONCE. */
export const MOCK_SEGMENTS: Array<RoadSegment> = generateSegments(MOCK_HEXES)

/** Road shapes passing through a given hex (capped at 5). */
export function segmentsForHex(hexId: string): Array<RoadSegment> {
  return MOCK_SEGMENTS.filter((s) => s.hexId === hexId).slice(0, 5)
}

/**
 * Distinct named OSM streets passing through a hex - for the honest "roads in
 * this cell" list. Dedupes the slice names and drops unnamed roads.
 */
export function roadNamesForHex(hexId: string): Array<string> {
  const seen = new Set<string>()
  for (const s of MOCK_SEGMENTS) {
    if (s.hexId !== hexId) continue
    if (!s.name || s.name === 'Unnamed road') continue
    seen.add(s.name)
  }
  return [...seen]
}