<#
.SYNOPSIS
  Build multiple ISR frequency / command budget variants for A/B testing.
  Each variant produces a separate tsconf_*.img disk image.

.DESCRIPTION
  Generates inc\variant_cfg.h for each variant, runs build.bat, copies
  the output image.  Restores the original variant_cfg.h afterward.

  NO source files are regex-patched — only variant_cfg.h is overwritten.

.NOTES
  C compilation is SLOW (~60 sec per variant).  Do NOT interrupt (Ctrl-C).
#>

Set-StrictMode -Version Latest
$ErrorActionPreference = 'Stop'

$root     = Split-Path -Parent $MyInvocation.MyCommand.Path   # src_sdcc
$projRoot = Split-Path -Parent $root                           # project root
$cfgFile  = "$root\inc\variant_cfg.h"

# ── Frequency tiers ──────────────────────────────────────────────────
# ISR_FREQ = 3 500 000 / Step;  Entries = 71 680 / Step;  TPF = Entries
# Shift = log2(44100 / Freq) rounded down
$freqTiers = @{
  '2734' = @{ Tag='';   Freq=2734; Step=1280; Entries=56; Shift=4; Mask='0x0F'; TPF=56;  Budgets=@(8,16)     }
  '1367' = @{ Tag='hf'; Freq=1367; Step=2560; Entries=28; Shift=5; Mask='0x1F'; TPF=28;  Budgets=@(8,16,32)  }
  '683'  = @{ Tag='qf'; Freq=683;  Step=5120; Entries=14; Shift=6; Mask='0x3F'; TPF=14;  Budgets=@(16,32,64) }
}

# ── Generate variants: 2+3+3 = 8 base × 2 NS = 16 total ─────────────
$baseVariants = @()
foreach ($ft in $freqTiers.Values | Sort-Object Freq -Descending) {
  foreach ($b in $ft.Budgets) {
    $suffix = if ($ft.Tag) { "_$($ft.Tag)" } else { '' }
    $name   = "b${b}${suffix}"
    $baseVariants += @{
      Name    = $name
      Budget  = $b
      Entries = $ft.Entries
      Step    = $ft.Step
      Freq    = $ft.Freq
      Shift   = $ft.Shift
      Mask    = $ft.Mask
      TPF     = $ft.TPF
      DataLoc = '0xB600'
      NS      = $false
    }
  }
}

# Auto-generate _ns (no short waits) clones
$nsVariants = foreach ($bv in $baseVariants) {
  $nv = $bv.Clone()
  $nv.Name = $bv.Name + '_ns'
  $nv.NS = $true
  $nv
}
$variants = $baseVariants + $nsVariants

# ── Save original variant_cfg.h ─────────────────────────────────────
$cfgBackup = Get-Content $cfgFile -Raw

function Restore-Cfg {
  Set-Content $script:cfgFile -Value $script:cfgBackup -NoNewline
}

# ── Helper: generate variant_cfg.h ──────────────────────────────────
function Write-VariantCfg($v) {
  $nsLine = if ($v.NS) { "#define VGM_NO_SHORT_WAITS" } else { "/* #define VGM_NO_SHORT_WAITS */" }
  $content = @"
/* variant_cfg.h -- AUTO-GENERATED by build_variants.ps1
 * Variant: $($v.Name)  Freq=$($v.Freq)Hz  Budget=$($v.Budget)  NS=$($v.NS)
 */
#ifndef VARIANT_CFG_H
#define VARIANT_CFG_H

#define ISR_FREQ              $($v.Freq)
#define ISR_TICKS_PER_FRAME   $($v.TPF)
#define VGM_SAMPLE_SHIFT      $($v.Shift)
#define VGM_SAMPLE_MASK       $($v.Mask)
#define VGM_FILL_CMD_BUDGET   $($v.Budget)

#define VARIANT_POS_ENTRIES   $($v.Entries)
#define VARIANT_POS_STEP      $($v.Step)
#define VARIANT_DATA_LOC      $($v.DataLoc)

$nsLine

#endif /* VARIANT_CFG_H */
"@
  Set-Content $script:cfgFile -Value $content -NoNewline
}

# ── Output directory ─────────────────────────────────────────────────
$outDir = "$projRoot\variants"
if (-not (Test-Path $outDir)) { New-Item -ItemType Directory -Path $outDir | Out-Null }

# ── Build loop ──────────────────────────────────────────────────────
$total   = $variants.Count
$idx     = 0
$results = @()

foreach ($v in $variants) {
  $idx++
  $name = $v.Name
  Write-Host "`n========== [$idx/$total] Building $name ==========" -ForegroundColor Cyan
  Write-Host "  Budget=$($v.Budget)  Freq=$($v.Freq)Hz  Entries=$($v.Entries)  Step=$($v.Step)  Shift=$($v.Shift)  TPF=$($v.TPF)  NS=$($v.NS)"

  # --- Generate variant_cfg.h ---
  Write-VariantCfg $v

  # --- Clean .rel files to force recompile ---
  Remove-Item "$root\build\*.rel" -ErrorAction SilentlyContinue

  # --- Run build ---
  Write-Host "  Building... (this takes ~60 sec)" -ForegroundColor Yellow
  $buildOut = cmd /c "cd /d $root && build.bat 2>&1"
  $buildOk  = $buildOut | Where-Object { $_ -match 'BUILD OK' }
  $buildFail = $buildOut | Where-Object { $_ -match 'FAIL|ERROR|overflow' }

  if ($buildFail -or -not $buildOk) {
    Write-Host "  *** BUILD FAILED for $name ***" -ForegroundColor Red
    $buildOut | Where-Object { $_ -match 'FAIL|error|warning|_CODE|_DATA|Last byte|overflow|variant_cfg' } |
      ForEach-Object { Write-Host "    $_" }
    $results += [pscustomobject]@{ Name=$name; Status='FAIL'; Code=0; Free=0 }
    continue
  }

  # --- Extract sizes from output ---
  $codeLine = $buildOut | Where-Object { $_ -match '_CODE' } | Select-Object -First 1
  $freeLine = $buildOut | Where-Object { $_ -match 'Free before' } | Select-Object -First 1
  $codeSize = if ($codeLine -match '(\d+)\s+bytes') { [int]$Matches[1] } else { 0 }
  $freeSize = if ($freeLine -match 'Free before C000:\s*(\d+)') { [int]$Matches[1] } else { 0 }

  # --- Show map ---
  $buildOut | Where-Object { $_ -match 'variant_cfg:|Section|_CODE|_DATA|_GSINIT|_HOME|_INITIAL|Last byte|Code:|Written.*WMF' } |
    ForEach-Object { Write-Host "  $_" }

  # --- Copy output image ---
  $srcImg = "$projRoot\tsconf.img"
  $dstImg = "$outDir\tsconf_$name.img"
  if (Test-Path $srcImg) {
    Copy-Item $srcImg $dstImg -Force
    Write-Host "  -> $dstImg" -ForegroundColor Green
  } else {
    Write-Host "  WARNING: tsconf.img not found" -ForegroundColor Yellow
  }
  # Also copy WMF
  $srcWmf = "$projRoot\DiskRef\WC\VGMPLAY.WMF"
  $dstWmf = "$outDir\VGMPLAY_$name.WMF"
  if (Test-Path $srcWmf) {
    Copy-Item $srcWmf $dstWmf -Force
  }

  $results += [pscustomobject]@{ Name=$name; Status='OK'; Code=$codeSize; Free=$freeSize }
}

# ── Restore original variant_cfg.h ──────────────────────────────────
Write-Host "`n========== Restoring original variant_cfg.h ==========" -ForegroundColor Cyan
Restore-Cfg
# Rebuild baseline to leave workspace clean
Remove-Item "$root\build\*.rel" -ErrorAction SilentlyContinue
Write-Host "  Rebuilding baseline..." -ForegroundColor Yellow
$null = cmd /c "cd /d $root && build.bat 2>&1"
Write-Host "  Done." -ForegroundColor Green

# ── Summary ──────────────────────────────────────────────────────────
Write-Host "`n========== VARIANT SUMMARY ==========" -ForegroundColor Cyan
$fmt = "{0,-18} {1,6} {2,6} {3,6} {4,3} {5,5} {6,5}"
Write-Host ($fmt -f 'Name','Budget','Freq','Code','NS','Free','St')
Write-Host ($fmt -f '----','------','----','----','--','----','--')
foreach ($r in $results) {
  $v = $variants | Where-Object { $_.Name -eq $r.Name }
  $nsTag = if ($v.NS) { 'yes' } else { ' - ' }
  $color = if ($r.Status -eq 'OK') { 'Green' } else { 'Red' }
  Write-Host ($fmt -f $r.Name, $v.Budget, $v.Freq, $r.Code, $nsTag, $r.Free, $r.Status) -ForegroundColor $color
}
Write-Host "`nImages in: $outDir"

# ── Generate README.txt ──────────────────────────────────────────────
$readme = @"
Variants of VGM player for A/B testing
=======================================

Parameters stored in inc\variant_cfg.h (single config file).
build_variants.ps1 regenerates variant_cfg.h for each variant.

Frequency tiers:
  qf     - quarter freq (ISR  683 Hz, step 5120, 14 ticks/frame)
  (none) - base freq    (ISR 2734 Hz, step 1280, 56 ticks/frame)
  hf     - half freq    (ISR 1367 Hz, step 2560, 28 ticks/frame)

Other tags:
  b<N>   - command budget (max commands between forced pauses)
  ns     - no short waits (0x70-0x7F pauses skipped)

"@

$readme += "{0,-30} {1,6} {2,8} {3,3} {4,6} {5,5} {6}`n" -f 'Image','Budget','Freq','NS','Code','Free','Status'
$readme += "{0,-30} {1,6} {2,8} {3,3} {4,6} {5,5} {6}`n" -f '-----','------','----','--','----','----','------'
foreach ($r in $results) {
  $v = $variants | Where-Object { $_.Name -eq $r.Name }
  $nsTag = if ($v.NS) { 'yes' } else { ' - ' }
  $freq  = "$($v.Freq)Hz"
  $readme += "{0,-30} {1,6} {2,8} {3,3} {4,6} {5,5} {6}`n" -f "tsconf_$($r.Name).img", $v.Budget, $freq, $nsTag, $r.Code, $r.Free, $r.Status
}

$readme += @"

What to test
------------
1. Higher budget helps (b32/b48/b64 vs b8/b16)
   -> Increase VGM_FILL_CMD_BUDGET.

2. Lower freq helps (hf or qf better than base)
   -> ISR overhead is the bottleneck, reduce frequency.

3. Higher freq helps (base better than hf/qf)
   -> More granular timing needed, keep higher ISR.

4. _ns variants better -> short waits 0x70-0x7F are the problem.

5. Nothing helps -> something else (OPL3 write delay, VGM parsing, etc.)
"@

Set-Content "$outDir\README.txt" -Value $readme -NoNewline -Encoding UTF8
Write-Host "`nREADME.txt written to $outDir" -ForegroundColor Green

Write-Host "`nLegend:" -ForegroundColor DarkGray
Write-Host "  qf = quarter freq (683 Hz)" -ForegroundColor DarkGray
Write-Host "  hf = half freq (1367 Hz)" -ForegroundColor DarkGray
Write-Host "  (no suffix) = base freq (2734 Hz)" -ForegroundColor DarkGray
Write-Host "  bN = budget N commands per ISR tick" -ForegroundColor DarkGray
Write-Host "  ns = no short waits (0x70-0x7F skipped)" -ForegroundColor DarkGray