'use client'

import {
  type AnyNode,
  type AnyNodeId,
  type GeometryContext,
  getEffectiveNode,
  nodeRegistry,
  type SurfaceRole,
  sceneRegistry,
  useLiveNodeOverrides,
  useScene,
} from '@pascal-app/core'
import { useFrame } from '@react-three/fiber'
import { useEffect, useRef } from 'react'
import { FrontSide, type Group, type Material, type Mesh, type Object3D } from 'three'
import {
  type ColorPreset,
  createSurfaceRoleMaterial,
  type RenderShading,
} from '../../lib/materials'
import useViewer from '../../store/use-viewer'

/**
 * Generic geometry system.
 *
 * For every node in `dirtyNodes` whose definition exposes `def.geometry`,
 * this system:
 *  1. Looks up the registered `Group` from `sceneRegistry` (mounted by the
 *     framework's `<ParametricNodeRenderer>`, or a custom renderer that
 *     opts into the same mount contract).
 *  2. Builds a `GeometryContext` from the current scene snapshot.
 *  3. Calls `def.geometry(node, ctx)` to get the new `Object3D`.
 *  4. Disposes the registered group's existing children + their geometries
 *     and materials.
 *  5. Reparents the returned object's children onto the registered group.
 *  6. Clears the dirty flag.
 *
 * This is the "no per-kind system needed" path documented in
 * `wiki/architecture/node-definitions.md`. A kind that only rebuilds on
 * dirty (shelf, item, fence segment, etc.) ships nothing more than a pure
 * `geometry` function — no `renderer.tsx`, no `system.tsx`.
 *
 * Kinds with `def.system` declared run their own systems *in addition* to
 * this one — animation + cascade + named-mesh material poking stay
 * kind-specific.
 *
 * Frame priority 2 mirrors the per-kind shelf system it replaces. Door
 * animation systems run at priority 2 today too, marking dirty so the
 * geometry rebuild lands at priority 3-4 next frame. Door/window/wall
 * still have their own systems (they need cross-cutting work this system
 * doesn't cover) — they coexist; this system only acts on kinds that
 * declare `def.geometry`.
 */
export const GeometrySystem = () => {
  const dirtyNodes = useScene((s) => s.dirtyNodes)
  const clearDirty = useScene((s) => s.clearDirty)
  const shading = useViewer((s) => s.shading)
  const textures = useViewer((s) => s.textures)
  const colorPreset = useViewer((s) => s.colorPreset)
  const sceneTheme = useViewer((s) => s.sceneTheme)
  const bumpGeometryRevision = useViewer((s) => s.bumpGeometryRevision)
  // The shared scene-material library, threaded into each builder's ctx so
  // pure geometry builders can resolve `scene:<id>` slot refs without
  // importing `useScene`.
  const sceneMaterials = useScene((s) => s.materials)
  // Per-node cache of the last-built geometry key (for kinds that declare
  // `def.geometryKey`). Lets us skip a dispose+rebuild when a node is dirty
  // but its geometry inputs are unchanged — e.g. an item reparenting onto a
  // shelf dirties the shelf without altering its boards.
  const builtGeometryKeyRef = useRef<Map<string, GeometryBuildCacheEntry>>(new Map())

  // Re-mark every geometry-backed node dirty whenever a viewer appearance
  // value changes, so `def.geometry` builders re-run and pick up the new
  // shading / texture / preset / theme. These four are deliberate re-run
  // TRIGGERS, not values read in the body — the effect re-fires on any
  // change. They're primitives (stable by value), so listing them is safe;
  // biome flags them as "unnecessary" because the body doesn't reference
  // them, but dropping them silently breaks appearance-mode switching.
  // biome-ignore lint/correctness/useExhaustiveDependencies: shading/textures/colorPreset/sceneTheme are intentional re-run triggers; removing them stops geometry from rebuilding on appearance change.
  useEffect(() => {
    const nodes = useScene.getState().nodes
    for (const node of Object.values(nodes)) {
      const def = nodeRegistry.get(node.type)
      if (def?.geometry) {
        useScene.getState().markDirty(node.id as AnyNodeId)
      }
    }
  }, [shading, textures, colorPreset, sceneTheme])

  // Editing a scene material must re-colour every geometry node that
  // references it through a `scene:<id>` slot ref. Such a node's
  // `geometryKey` is unchanged (only the referenced material's contents
  // moved), so clear its cached key to defeat the skip in the rebuild loop,
  // then mark it dirty. Scoped to nodes carrying a `scene:` ref so an
  // unrelated material edit doesn't churn the whole scene.
  useEffect(() => {
    void sceneMaterials
    const nodes = useScene.getState().nodes
    for (const node of Object.values(nodes)) {
      const def = nodeRegistry.get(node.type)
      if (!def?.geometry) continue
      if (!nodeReferencesSceneMaterial(node)) continue
      builtGeometryKeyRef.current.delete(node.id)
      useScene.getState().markDirty(node.id as AnyNodeId)
    }
  }, [sceneMaterials])

  useFrame(() => {
    if (dirtyNodes.size === 0) return
    const nodes = useScene.getState().nodes
    let rebuiltGeometry = false

    // Phase 1 — group dirty nodes by (kind, parentId). Kinds that
    // declare `def.computeLevelData` get one batch precompute per
    // group; the result lands in `ctx.levelData` for every node in
    // the same batch. Avoids O(N²) recomputation when many siblings
    // of the same kind are dirty in one frame (wall mitering is the
    // motivating case).
    type BatchKey = string // `${kind}::${parentId ?? ''}`
    const batches = new Map<
      BatchKey,
      { kind: string; parentId: AnyNodeId | null; ids: AnyNodeId[] }
    >()
    const dirtyIds: AnyNodeId[] = []
    dirtyNodes.forEach((id) => {
      const node = nodes[id]
      if (!node) return
      const def = nodeRegistry.get(node.type)
      if (!def?.geometry) return
      dirtyIds.push(id as AnyNodeId)
      const parentId = (node.parentId ?? null) as AnyNodeId | null
      const key: BatchKey = `${node.type}::${parentId ?? ''}`
      const existing = batches.get(key)
      if (existing) existing.ids.push(id as AnyNodeId)
      else batches.set(key, { kind: node.type, parentId, ids: [id as AnyNodeId] })
    })

    // Phase 2 — for each batch whose kind declares `computeLevelData`,
    // collect every sibling in the level + run the precompute once.
    const levelDataByBatch = new Map<BatchKey, unknown>()
    for (const [key, batch] of batches) {
      const def = nodeRegistry.get(batch.kind)
      if (!def?.computeLevelData) continue
      const siblings: AnyNode[] = []
      if (batch.parentId) {
        const parent = nodes[batch.parentId]
        const childIds = (parent as unknown as { children?: AnyNodeId[] })?.children
        if (Array.isArray(childIds)) {
          for (const cid of childIds) {
            const child = nodes[cid]
            if (child?.type === batch.kind) siblings.push(child)
          }
        }
      } else {
        for (const node of Object.values(nodes)) {
          if (node?.type === batch.kind && !node.parentId) siblings.push(node)
        }
      }
      levelDataByBatch.set(
        key,
        (def.computeLevelData as (s: ReadonlyArray<AnyNode>) => unknown)(siblings),
      )
    }

    // Phase 3 — per-node rebuild. Each node receives its batch's
    // precomputed `levelData` in ctx.
    for (const id of dirtyIds) {
      const node = nodes[id]
      if (!node) continue

      const def = nodeRegistry.get(node.type)
      const builder = def?.geometry
      if (!builder) continue

      const group = sceneRegistry.nodes.get(id) as Group | undefined
      if (!group) continue // mount hasn't run — keep dirty for next frame

      // Merge any live drag override into the node so resize arrows /
      // 2D affordances see their in-flight patch on every pointer move
      // — zustand only learns about the final value on commit. Mirrors
      // the WallSystem / DoorSystem / WindowSystem hook-up; any kind
      // that drives its mesh through `def.geometry` (fence, shelf, item)
      // now smooths drags through this single line.
      const effectiveNode = getEffectiveNode(node)

      // Skip the rebuild when the geometry inputs are unchanged (kinds that
      // opt in via `def.geometryKey`). Fold in the global rendering inputs so
      // a theme / shading change — which re-dirties every geometry node — is
      // never skipped. This kills the board remount + pointer enter/leave
      // churn when an item reparents onto a shelf.
      if (def.geometryKey) {
        const childLiveOverrideKey = liveChildOverrideKey(node)
        const builtKey = `${shading}|${textures}|${colorPreset}|${sceneTheme}|${def.geometryKey(effectiveNode)}|${childLiveOverrideKey}`
        if (shouldReuseGeometryBuild(builtGeometryKeyRef.current, id, group, builtKey)) {
          clearDirty(id as AnyNodeId)
          continue
        }
      }

      const parentId = (node.parentId ?? null) as AnyNodeId | null
      const key: BatchKey = `${node.type}::${parentId ?? ''}`
      const levelData = levelDataByBatch.get(key)
      const ctx = buildGeometryContext(effectiveNode, nodes, levelData, sceneMaterials)

      // The builder is typed against the kind's specific node — at the
      // generic system level we lose that refinement, so the cast lands
      // here. Builders are responsible for trusting their schema.
      const built = (
        builder as (
          n: AnyNode,
          c: GeometryContext,
          shading: RenderShading,
          textures: boolean,
          colorPreset: ColorPreset,
          sceneTheme: string,
        ) => { children: unknown[] }
      )(effectiveNode, ctx, shading, textures, colorPreset, sceneTheme) as unknown as Group

      if (!textures && def.surfaceRole) {
        applyDefaultSurfaceRole(built, def.surfaceRole, colorPreset, sceneTheme)
      }

      disposeChildren(group)
      for (const child of [...built.children]) {
        markGeometryBuildOutput(child)
        group.add(child)
      }
      rebuiltGeometry = true
      // NOTE: we intentionally do NOT reset `group.position` / `group.rotation`
      // here. The `ParametricNodeRenderer` binds them via JSX (`position={...}`
      // / `rotation={...}`) driven by `useLiveTransforms` during drag and
      // `node.position` / `node.rotation` after commit. Zeroing them out
      // during a rebuild would clobber the React-applied transform — and
      // because the renderer doesn't necessarily re-render on the rebuild
      // tick, R3F wouldn't re-apply the props, leaving the group stuck at
      // origin. Geometry builders are expected to emit local-space children.

      clearDirty(id as AnyNodeId)
    }
    if (rebuiltGeometry) bumpGeometryRevision()
  }, 2)

  return null
}

function liveChildOverrideKey(node: AnyNode): string {
  const childIds = (node as unknown as { children?: AnyNodeId[] }).children
  if (!Array.isArray(childIds) || childIds.length === 0) return ''

  const overrides = useLiveNodeOverrides.getState().overrides
  const entries: Array<[AnyNodeId, unknown]> = []
  for (const childId of childIds) {
    const override = overrides.get(childId)
    if (override) entries.push([childId, override])
  }
  return entries.length === 0 ? '' : JSON.stringify(entries)
}

function nodeReferencesSceneMaterial(node: AnyNode): boolean {
  const slots = (node as { slots?: Record<string, string> }).slots
  if (!slots) return false
  for (const ref of Object.values(slots)) {
    if (typeof ref === 'string' && ref.startsWith('scene:')) return true
  }
  return false
}

function buildGeometryContext(
  node: AnyNode,
  nodes: Record<string, AnyNode>,
  levelData: unknown,
  materials: GeometryContext['materials'],
): GeometryContext {
  const resolve = <N = AnyNode>(id: AnyNodeId): N | undefined => {
    const resolved = nodes[id]
    return resolved ? (getEffectiveNode(resolved) as N) : undefined
  }

  const childIds = (node as unknown as { children?: AnyNodeId[] }).children
  const children: AnyNode[] = Array.isArray(childIds)
    ? childIds.map((cid) => resolve<AnyNode>(cid)).filter((n): n is AnyNode => n !== undefined)
    : []

  const parentId = node.parentId as AnyNodeId | null
  const parent: AnyNode | null = parentId ? (resolve<AnyNode>(parentId) ?? null) : null

  // Siblings = same kind, same parent, excluding self. Walks the parent's
  // children array; falls back to scanning the whole scene if the parent
  // doesn't carry a `children` list (rare — most parents do).
  let siblings: AnyNode[] = []
  if (parent) {
    const parentChildIds = (parent as unknown as { children?: AnyNodeId[] }).children
    if (Array.isArray(parentChildIds)) {
      for (const sid of parentChildIds) {
        if (sid === node.id) continue
        const s = resolve<AnyNode>(sid)
        if (s && s.type === node.type) siblings.push(s)
      }
    } else {
      siblings = Object.values(nodes)
        .filter((n) => n !== node && n.type === node.type && n.parentId === parentId)
        .map((n) => getEffectiveNode(n))
    }
  }

  return { resolve, children, siblings, parent, levelData, materials }
}

function disposeChildren(group: Group) {
  // Only dispose meshes the geometry builder produced on the previous
  // rebuild (marked via `userData.__fromGeometry`). React-managed
  // children (hosted node renderers) get left in place — they have
  // their own React-driven lifecycle and would lose their meshes /
  // materials if we disposed them here.
  for (const child of [...group.children]) {
    const fromGeometry = (child as { userData?: { __fromGeometry?: boolean } }).userData
      ?.__fromGeometry
    if (!fromGeometry) continue
    group.remove(child)
    const mesh = child as Partial<Mesh> & { geometry?: { dispose?: () => void } }
    if (mesh.geometry?.dispose) mesh.geometry.dispose()
    if ('material' in mesh) {
      const m = (mesh as { material: unknown }).material
      if (Array.isArray(m)) {
        for (const mat of m) {
          if (isCachedMaterial(mat)) continue
          if (mat && typeof (mat as { dispose?: () => void }).dispose === 'function') {
            ;(mat as { dispose: () => void }).dispose()
          }
        }
      } else if (isCachedMaterial(m)) {
      } else if (m && typeof (m as { dispose?: () => void }).dispose === 'function') {
        ;(m as { dispose: () => void }).dispose()
      }
    }
  }
}

function applyDefaultSurfaceRole(
  root: Group,
  defaultRole: SurfaceRole,
  colorPreset: ColorPreset,
  sceneTheme?: string,
) {
  root.traverse((child) => {
    const mesh = child as Partial<Mesh> & {
      material?: Material | Material[]
      userData: Record<string, unknown>
    }
    if (!('material' in mesh) || !mesh.material) return

    const role = getMeshSurfaceRole(mesh.userData.surfaceRole, defaultRole)
    mesh.userData.surfaceRole = role
    mesh.material = createSurfaceRoleMaterial(
      role,
      colorPreset,
      getMaterialSide(mesh.material),
      sceneTheme,
    )
  })
}

function getMeshSurfaceRole(value: unknown, fallback: SurfaceRole): SurfaceRole {
  return typeof value === 'string' && isSurfaceRole(value) ? value : fallback
}

function isSurfaceRole(value: string): value is SurfaceRole {
  return (
    value === 'wall' ||
    value === 'floor' ||
    value === 'ceiling' ||
    value === 'roof' ||
    value === 'joinery' ||
    value === 'glazing' ||
    value === 'furnishing'
  )
}

function getMaterialSide(material: Material | Material[]): Material['side'] {
  const source = Array.isArray(material) ? material[0] : material
  return source?.side ?? FrontSide
}

function isCachedMaterial(value: unknown): boolean {
  return Boolean(
    (value as { userData?: { __pascalCachedMaterial?: boolean } } | null)?.userData
      ?.__pascalCachedMaterial,
  )
}

export default GeometrySystem

export type GeometryBuildCacheEntry = {
  group: Group
  key: string
}

export function markGeometryBuildOutput(child: Object3D): void {
  // Tag the builder subtree so paint previews can reach nested meshes (for
  // example a cabinet sink faucet handle), while disposal still removes only
  // top-level builder children from the registered group.
  child.traverse((object) => {
    object.userData = {
      ...object.userData,
      __fromGeometry: true,
    }
  })
}

export function shouldReuseGeometryBuild(
  cache: Map<string, GeometryBuildCacheEntry>,
  id: string,
  group: Group,
  key: string,
): boolean {
  const cached = cache.get(id)
  if (cached?.group === group && cached.key === key) return true
  cache.set(id, { group, key })
  return false
}