## OFFLINE — does the time-indexed bullet heat (TR_TFIL_HEAT_TIME=1) actually
## open free zones? READ-ONLY: no live battles, no change to shipped defaults.
##
## Reuses the machinery of `measure_tfil_heat_field.nim` (jobs 42/43): drive the
## REAL `TFILModule.computeMove` over the committed DrussGT fixtures (so bullet
## tracking, reachable hull and cached inside-tiles are identical to the live
## mover) and read its private `lava` via `include`.
##
## Because `lava` depends only on bullets/enemies/walls/pillars — NOT on the
## bot's picks or the RNG — the OFF and ON replays differ in nothing but the
## heat function. That makes the before/after a clean static-field comparison.
##
## Metrics, per the user's question:
##   * fraction of grid tiles above PathDangerThreshold (10)
##   * largest contiguous safe region (4-connected), in tiles
##   * mean grid-step / px distance from a tile to the nearest safe tile
## plus the corridor reach: the `dt` (and px) at which a bullet's corridor heat
## falls back to <= threshold, vs the old wall-to-wall corridor.
##
## Run:
##   nim c -r --path:common_libs common_libs/tests/measure_tfil_heat_time.nim \
##       [fixture.jsonl ...]

import std/[os, strformat, math, deques, sets, json]
import gun_harness/offline_range
# Private-field access: include (do NOT import) the shipped mover.
include movements/the_floor_is_lava

const SafeThreshold = 10.0

type
  FieldMetrics = object
    fracOver:      float   ## tiles with lava > 10 / all tiles
    largestSafe:   int     ## largest 4-connected safe region, tiles
    meanDistAll:   float   ## mean nearest-safe-tile distance over ALL tiles
    meanDistUnsafe: float  ## ... over the unsafe tiles only
    hasSafe:       bool

  RunStats = object
    ticks:            int
    sumFracOver:      float
    sumLargestSafe:   float
    maxLargestSafe:   int
    sumDistAll:       float
    sumDistUnsafe:    float
    noSafeTicks:      int
    # corridor reach (ON model only)
    corridors:        int
    sumReachDt:       float
    sumReachPx:       float
    sumOldPx:         float
    histLo:           array[6, int]  ## reach px buckets: <50,50-100,... ,>=250

proc loadRoundStarts(fixturePath: string): HashSet[int] =
  result = initHashSet[int]()
  let side = currentSourcePath().parentDir.parentDir.parentDir /
             "tools" / "fixtures" / "drussgt_meta" /
             (extractFilename(fixturePath) & ".rounds.json")
  if not fileExists(side): return
  let root = parseFile(side)
  if not root.hasKey("rounds"): return
  for r in root["rounds"]:
    if r.hasKey("startTick"): result.incl r["startTick"].getInt()

# ── the three field metrics, on a real `m.lava` ──────────────────────────────
proc fieldMetrics(m: TFILModule): FieldMetrics =
  let n = m.cols * m.rows
  var over = 0
  var safe = newSeq[bool](n)
  for i in 0..<n:
    if m.lava[i] > SafeThreshold: inc over
    else: safe[i] = true
  result.fracOver = over.float / n.float
  result.hasSafe = over < n

  const Neigh = [(-1, 0), (1, 0), (0, -1), (0, 1)]

  # multi-source BFS from every safe tile -> distance to nearest safe tile
  var dist = newSeq[int](n)
  var q = initDeque[int]()
  for i in 0..<n:
    if safe[i]:
      dist[i] = 0
      q.addLast(i)
    else:
      dist[i] = -1
  while q.len > 0:
    let cur = q.popFirst()
    let cc = cur mod m.cols
    let rr = cur div m.cols
    for (dc, dr) in Neigh:
      let nc = cc + dc
      let nr = rr + dr
      if nc < 0 or nc >= m.cols or nr < 0 or nr >= m.rows: continue
      let ni = nr * m.cols + nc
      if dist[ni] < 0:
        dist[ni] = dist[cur] + 1
        q.addLast(ni)
  var sumAll = 0.0
  var sumUnsafe = 0.0
  var nUnsafe = 0
  for i in 0..<n:
    if dist[i] >= 0: sumAll += dist[i].float
    if (not safe[i]) and dist[i] >= 0:
      sumUnsafe += dist[i].float
      inc nUnsafe
  result.meanDistAll = sumAll / n.float
  result.meanDistUnsafe = if nUnsafe > 0: sumUnsafe / nUnsafe.float else: 0.0

  # largest 4-connected safe region
  var seen = newSeq[bool](n)
  var best = 0
  for i in 0..<n:
    if safe[i] and not seen[i]:
      var size = 0
      var q2 = initDeque[int]()
      q2.addLast(i); seen[i] = true
      while q2.len > 0:
        let cur = q2.popFirst()
        inc size
        let cc = cur mod m.cols
        let rr = cur div m.cols
        for (dc, dr) in Neigh:
          let nc = cc + dc
          let nr = rr + dr
          if nc < 0 or nc >= m.cols or nr < 0 or nr >= m.rows: continue
          let ni = nr * m.cols + nc
          if safe[ni] and not seen[ni]:
            seen[ni] = true
            q2.addLast(ni)
      if size > best: best = size
  result.largestSafe = best

# ── replay one fixture under one heat model ──────────────────────────────────
proc analyse(path: string, timeOn: bool, tau, gain: float): RunStats =
  putEnv("TR_TFIL_HEAT_TIME", if timeOn: "1" else: "0")
  putEnv("TR_TFIL_HEAT_TAU", $tau)
  putEnv("TR_TFIL_HEAT_POWER_GAIN", $gain)
  loadTfilHeatEnv()

  let fx     = loadFixture(path)
  let starts = loadRoundStarts(path)
  var m = initTFIL()
  for si in 0..<fx.states.len:
    let ws = fx.states[si]
    if si == 0 or si in starts: m.resetRound()
    discard m.computeMove(ws)
    inc result.ticks

    let fm = fieldMetrics(m)
    result.sumFracOver    += fm.fracOver
    result.sumLargestSafe += fm.largestSafe.float
    result.maxLargestSafe = max(result.maxLargestSafe, fm.largestSafe)
    result.sumDistAll     += fm.meanDistAll
    result.sumDistUnsafe  += fm.meanDistUnsafe
    if not fm.hasSafe: inc result.noSafeTicks

    if timeOn:
      # Corridor reach: heat along the corridor is
      #   CorridorHeat * mag * exp(-dt/tau); it stops blocking at dt* where it
      #   falls to SafeThreshold, i.e. dt* = -tau*ln(thr/(CorridorHeat*mag)).
      for b in m.bullets:
        let cg = corridorGeom(b, m.arenaWidth, m.arenaHeight)
        if cg.tMin == 0.0: continue
        let speed = sqrt(b.velX * b.velX + b.velY * b.velY)
        let mag = 1.0 + gain * (b.power / 3.0)
        let near = CorridorHeat * mag
        var reachPx = 0.0
        var reachDt = 0.0
        if near > SafeThreshold:
          reachDt = -tau * ln(SafeThreshold / near)
          reachPx = reachDt * speed
        inc result.corridors
        result.sumReachDt += reachDt
        result.sumReachPx += reachPx
        result.sumOldPx   += cg.tMin
        let bkt = if reachPx < 50.0: 0 elif reachPx < 100.0: 1
                  elif reachPx < 150.0: 2 elif reachPx < 200.0: 3
                  elif reachPx < 250.0: 4 else: 5
        inc result.histLo[bkt]

proc f2(x: float): string = &"{x:.2f}"

proc reportOne(name: string, ticks: int, off, on: RunStats) =
  let n = max(1, ticks).float
  echo ""
  echo "═══════════════════════════════════════════════════════════════════════════"
  echo &"FILE {name}  ticks={ticks}"
  echo "                               OFF (shipped flat)   ON (time-indexed)"
  echo &"  frac tiles > 10            {f2(off.sumFracOver/n):>19} {f2(on.sumFracOver/n):>19}"
  echo &"  largest safe region (tiles){f2(off.sumLargestSafe/n):>19} {f2(on.sumLargestSafe/n):>19}" &
       &"   (max {off.maxLargestSafe} -> {on.maxLargestSafe})"
  echo &"  mean dist->safe (all tiles){f2(off.sumDistAll/n):>19} {f2(on.sumDistAll/n):>19}" &
       &"  grid-steps  (=x36 px: {f2(off.sumDistAll/n*36.0)} -> {f2(on.sumDistAll/n*36.0)})"
  echo &"  mean dist->safe (unsafe)   {f2(off.sumDistUnsafe/n):>19} {f2(on.sumDistUnsafe/n):>19}"
  echo &"  ticks with NO safe tile    {off.noSafeTicks:>19} {on.noSafeTicks:>19}"
  if on.corridors > 0:
    echo ""
    echo "  corridor reach under the ON model (where it stops blocking):"
    echo &"    mean reach dt  = {f2(on.sumReachDt/on.corridors.float)} ticks"
    echo &"    mean reach px  = {f2(on.sumReachPx/on.corridors.float)} px" &
         &"   vs mean old wall-to-wall corridor = {f2(on.sumOldPx/on.corridors.float)} px"
    echo &"    retained fraction = {f2(on.sumReachPx/on.sumOldPx*100.0)}% of the old corridor length"
    const Names = ["<50", "50-100", "100-150", "150-200", "200-250", ">=250"]
    for i in 0..5:
      echo &"    reach {Names[i]:>7} px : {on.histLo[i]} of {on.corridors} bullet-ticks"

proc main() =
  var files: seq[string]
  for i in 1..paramCount():
    files.add paramStr(i)
  if files.len == 0:
    let dir = currentSourcePath().parentDir.parentDir.parentDir / "tools" / "fixtures"
    files = @[
      dir / "tr_drussgt_vs_modularbot.jsonl",
      dir / "tr_drussgt_vs_modularbot_shield.jsonl",
      dir / "tr_drussgt_vs_spinbot.jsonl",
      dir / "tr_drussgt_vs_corners.jsonl",
    ]

  const Tau  = 9.0
  const Gain = 1.0
  # Sweep hooks: HT_TAU / HT_GAIN override the constants without a rebuild.
  var tau  = Tau
  var gain = Gain
  if existsEnv("HT_TAU"):  tau  = parseFloat(getEnv("HT_TAU"))
  if existsEnv("HT_GAIN"): gain = parseFloat(getEnv("HT_GAIN"))
  echo &"# Time-indexed bullet heat — offline field comparison (tau={tau} ticks, gain={gain})"
  var ticks = 0
  for f in files:
    if not fileExists(f):
      stderr.writeLine("missing fixture: " & f)
      continue
    let off = analyse(f, timeOn = false, tau = tau, gain = gain)
    let on  = analyse(f, timeOn = true,  tau = tau, gain = gain)
    reportOne(extractFilename(f), off.ticks, off, on)
    ticks += off.ticks
  echo ""
  echo &"# done: {ticks} fixture ticks across {files.len} files (OFF vs ON)"

when isMainModule:
  main()