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## Deterministic avatar system (avatar-v1).
##
## canonical seed = HKDF-SHA256(ikm=DID, salt="freeq-world-avatar", info="avatar-v1")
## All traits are abstract — nothing is inferred from profile data.

import std/[math, tables]
import ./sha256

type
  Traits* = OrderedTable[string, string]

  Avatar* = object
    schema*: string
    did*: string
    baseGenerator*: string
    canonicalSeedHex*: string
    traits*: Traits

  Facing* = enum
    fSouth = "south", fNorth = "north", fEast = "east", fWest = "west"

  Sprite* = object
    width*, height*: int
    pixels*: seq[int]     ## palette indices
    palette*: seq[string]

const traitKeys* = [
  "body_silhouette", "head_shape", "skin_palette", "hair_shape", "hair_palette",
  "eye_pixels", "shirt_jacket", "pants_skirt", "shoes", "accessory",
  "idle_movement", "walk_cadence", "speech_sound", "accent_palette",
  "arrival_effect", "musical_leitmotif"]

const options*: array[15, (string, seq[string])] = [
  ("body_silhouette", @["slim", "broad", "round", "tall", "compact", "angular"]),
  ("head_shape", @["round", "square", "oval", "wide"]),
  # stylized fictional palette — deliberately includes non-naturalistic hues
  ("skin_palette", @["#e8b48c", "#c68863", "#8d5a3b", "#5c3a26", "#f4d6b8",
                     "#9fb8ad", "#b7a6d9", "#7d9c6f"]),
  ("hair_shape", @["crop", "spikes", "bob", "long", "curls", "mohawk", "bald", "bun"]),
  ("hair_palette", @["#2b2b3a", "#5a3825", "#c9a227", "#b8434e", "#3f7cac",
                     "#67c26b", "#e8e6df", "#8447ad"]),
  ("eye_pixels", @["dot", "wide", "wink", "visor"]),
  ("shirt_jacket", @["#3f7cac", "#b8434e", "#67c26b", "#c9a227", "#8447ad",
                     "#3a9188", "#d97b29", "#6d7680"]),
  ("pants_skirt", @["#31394d", "#5a3825", "#3a5a40", "#6b3a55", "#444444", "#7a5c99"]),
  ("shoes", @["#1e1e28", "#5a3825", "#b8434e", "#e8e6df"]),
  ("accessory", @["none", "hat", "glasses", "scarf", "antenna", "flower",
                  "headphones", "badge"]),
  ("idle_movement", @["bob", "sway", "blink", "tap"]),
  ("walk_cadence", @["steady", "bouncy", "brisk", "ambling"]),
  ("speech_sound", @["beep", "blip", "burble", "chirp", "hum"]),
  ("accent_palette", @["#ffd166", "#06d6a0", "#ef476f", "#118ab2", "#f78c6b", "#9b5de5"]),
  ("arrival_effect", @["sparkle", "dissolve", "drop", "teleport-rings"])]

func optionsFor*(key: string): seq[string] =
  for (k, v) in options:
    if k == key: return v
  raise newException(KeyError, "no options for trait " & key)

type Prng* = object
  a, b, c, d: uint32

func u32le(seed: openArray[byte], i: int): uint32 =
  for k in 0 ..< 4:
    result = result or (uint32(seed[i + k]) shl (8 * k))

func initPrng*(seed: openArray[byte]): Prng =
  ## sfc32 seeded from the first 16 bytes of `seed` — bit-identical to the
  ## JavaScript original the fixture was generated with.
  Prng(a: u32le(seed, 0), b: u32le(seed, 4), c: u32le(seed, 8), d: u32le(seed, 12))

func next*(p: var Prng): float =
  ## Next double in [0, 1).
  let t = p.a + p.b + p.d
  let d = p.d + 1
  let a = p.b xor (p.b shr 9)
  let b = p.c + (p.c shl 3)
  let c = ((p.c shl 21) or (p.c shr 11)) + t
  p = Prng(a: a, b: b, c: c, d: d)
  float(t) / 4294967296.0

func pick*(p: var Prng, opts: openArray[string]): string =
  let i = int(floor(p.next() * float(opts.len)))
  opts[min(i, opts.len - 1)]

func canonicalSeed*(did: string): seq[byte] =
  ## 32-byte canonical seed for a DID.
  hkdf(did, "freeq-world-avatar", "avatar-v1", 32)

func deriveAvatar*(did: string): Avatar =
  let seed = canonicalSeed(did)
  var rng = initPrng(seed)
  var traits: Traits
  for key in traitKeys:
    traits[key] =
      if key == "musical_leitmotif":
        # pointer to the leitmotif derivation (own HKDF domain)
        "motif-v1"
      else:
        pick(rng, optionsFor(key))
  Avatar(schema: "freeq.at/profile/avatar/v1",
         did: did,
         baseGenerator: "avatar-v1",
         canonicalSeedHex: toHex(seed),
         traits: traits)

const
  W* = 16
  H* = 24

const
  SKIN = 1
  HAIR = 2
  SHIRT = 3
  PANTS = 4
  SHOE = 5
  INK = 6
  ACCENT = 7
  WHITE = 8

func renderSpritePixels*(av: Avatar, facing = fSouth, frame = 0): Sprite =
  ## Procedural 16x24 pixel body. Rows: hair/head 0-9, torso 10-17, legs 18-21,
  ## shoes 22-23. Facing changes the face; walk frames swing arms and legs.
  let t = av.traits
  var px = newSeq[int](W * H)

  proc put(x, y, c: int) =
    if x >= 0 and x < W and y >= 0 and y < H:
      px[y * W + x] = c

  proc hspan(x0, x1, y, c: int) =
    for x in x0 .. x1:
      put(x, y, c)

  let
    silhouette = t["body_silhouette"]
    bodyW = if silhouette in ["broad", "round"]: 10
            elif silhouette == "slim": 6
            else: 8
    bodyX0 = (W - bodyW) div 2
    bodyX1 = bodyX0 + bodyW - 1

    headShape = t["head_shape"]
    headW = if headShape == "wide": 10 else: 8
    headX0 = (W - headW) div 2
    headX1 = headX0 + headW - 1
    headTop = if silhouette == "tall": 1 else: 2
    hair = t["hair_shape"]
    acc = t["accessory"]

  # head
  for y in headTop ..< 10:
    let shrink = if headShape in ["round", "oval"] and (y == headTop or y == 9): 1 else: 0
    hspan(headX0 + shrink, headX1 - shrink, y, SKIN)

  # hair
  if hair != "bald":
    hspan(headX0, headX1, headTop, HAIR)
    hspan(headX0, headX1, headTop + 1, HAIR)
    if hair in ["spikes", "mohawk"]:
      let
        mohawk = hair == "mohawk"
        start = headX0 + (if mohawk: headW div 2 - 1 else: 0)
        stop = if mohawk: headX0 + headW div 2 else: headX1
        step = if mohawk: 1 else: 2
      var x = start
      while x <= stop:
        put(x, headTop - 1, HAIR)
        x += step
    if hair in ["bob", "long", "curls"]:
      put(headX0, headTop + 2, HAIR)
      put(headX1, headTop + 2, HAIR)
      put(headX0, headTop + 3, HAIR)
      put(headX1, headTop + 3, HAIR)
      if hair == "long":
        put(headX0, headTop + 4, HAIR)
        put(headX1, headTop + 4, HAIR)
    if hair == "bun":
      put(W div 2, headTop - 1, HAIR)

  # face (not shown when facing north)
  if facing != fNorth:
    let
      eyeY = headTop + 4
      eyes = t["eye_pixels"]
      mid = W div 2
      eyeL = case facing
             of fEast: mid
             of fWest: headX0 + 1
             else: headX0 + 2
      eyeR = case facing
             of fEast: headX1 - 1
             of fWest: mid - 1
             else: headX1 - 2
    if eyes == "visor":
      hspan(eyeL, eyeR, eyeY, ACCENT)
    else:
      put(eyeL, eyeY, INK)
      if eyes != "wink":
        put(eyeR, eyeY, INK)
      if eyes == "wide":
        put(eyeL, eyeY - 1, WHITE)
        put(eyeR, eyeY - 1, WHITE)
  elif hair != "bald":
    # back of head is hair
    for y in headTop ..< 9:
      hspan(headX0, headX1, y, HAIR)

  # torso
  for y in 10 ..< 18:
    hspan(bodyX0, bodyX1, y, SHIRT)
  # accent stripe
  hspan(bodyX0, bodyX1, 13, ACCENT)

  # arms (swing with walk frame)
  let swing = case frame
              of 0: 0
              of 1: 1
              else: -1
  put(bodyX0 - 1, 11 + swing, SKIN)
  put(bodyX0 - 1, 12 + swing, SKIN)
  put(bodyX1 + 1, 11 - swing, SKIN)
  put(bodyX1 + 1, 12 - swing, SKIN)

  # legs
  let
    legW = max(2, bodyW div 2 - 1)
    gap = case frame
          of 0: 2
          of 1: 4
          else: 0
    legL0 = W div 2 - gap div 2 - legW
    legR0 = W div 2 + int(ceil(float(gap) / 2.0))
  for y in 18 ..< 22:
    hspan(legL0, legL0 + legW - 1, y, PANTS)
    hspan(legR0, legR0 + legW - 1, y, PANTS)
  for y in 22 ..< 24:
    hspan(legL0, legL0 + legW - 1, y, SHOE)
    hspan(legR0, legR0 + legW - 1, y, SHOE)

  # accessory
  case acc
  of "hat":
    hspan(headX0 - 1, headX1 + 1, headTop, ACCENT)
    hspan(headX0, headX1, headTop - 1, ACCENT)
  of "antenna":
    put(W div 2, headTop - 1, INK)
    put(W div 2, headTop - 2, ACCENT)
  of "scarf":
    hspan(bodyX0, bodyX1, 10, ACCENT)
  of "glasses":
    if facing != fNorth:
      hspan(headX0 + 1, headX1 - 1, headTop + 4, INK)
  of "headphones":
    put(headX0 - 1, headTop + 3, ACCENT)
    put(headX1 + 1, headTop + 3, ACCENT)
  of "flower":
    put(headX1, headTop + 1, ACCENT)
  of "badge":
    put(bodyX0 + 1, 11, ACCENT)
  else: discard

  Sprite(width: W, height: H, pixels: px,
         palette: @["transparent", t["skin_palette"], t["hair_palette"],
                    t["shirt_jacket"], t["pants_skirt"], t["shoes"],
                    "#14141c", # outline/eyes
                    t["accent_palette"], "#ffffff"])

func spriteHash*(av: Avatar): string =
  ## Deterministic content hash over all four facings — conformance fixture value.
  var bs: seq[byte]
  for facing in [fSouth, fNorth, fEast, fWest]:
    let s = renderSpritePixels(av, facing, 0)
    for p in s.pixels:
      bs.add byte(p and 255)
    for color in s.palette:
      for ch in color:
        bs.add byte(ch)
  toHex(digest(bs))