--[[
  midigrid_lib.lua -- shared library for the MIDI Grid quick-entry mode.

  Design notes:
    * No window, no gfx. All feedback goes through OSARA speech.
    * The cursor is Reaper's OWN edit cursor (time) plus the MIDI editor's
      active_note_row (pitch). We never keep a private cursor, so grid mode
      and normal OSARA editing can be interleaved freely.
    * Grid size is read from MIDI_GetGrid(), so the user's existing
      grid-size keybindings (1-9 in the MIDI editor) drive it.
    * Persistent state is only: active, hold, root, scale, vel, chan.
]]

local M = {}

local EXT = "midigrid"

--------------------------------------------------------------------- state

function M.get(k, default)
  local v = reaper.GetExtState(EXT, k)
  if v == "" then return default end
  return v
end

function M.getNum(k, default)
  return tonumber(M.get(k, tostring(default))) or default
end

function M.set(k, v)
  reaper.SetExtState(EXT, k, tostring(v), true)
end

-- Transient state (preview requests, daemon heartbeat). Never persisted:
-- these change on every keypress and must not hit reaper.ini.
function M.setTemp(k, v) reaper.SetExtState(EXT, k, tostring(v), false) end

function M.getTemp(k, default)
  local v = reaper.GetExtState(EXT, k)
  if v == "" then return default end
  return v
end

function M.isActive() return M.get("active", "0") == "1" end
function M.isHold()   return M.get("hold",   "0") == "1" end

--------------------------------------------------------------------- speech

-- OSARA exposes osara_outputMessage; fall back to the console if absent so
-- the scripts are still debuggable on a machine without OSARA.
function M.say(msg)
  if reaper.APIExists("osara_outputMessage") then
    reaper.osara_outputMessage(msg)
  else
    reaper.ShowConsoleMsg(tostring(msg) .. "\n")
  end
end

--------------------------------------------------------------- editor/take

-- Returns hwnd, take for the active MIDI editor, or nil plus a reason.
function M.editor()
  local hwnd = reaper.MIDIEditor_GetActive()
  if not hwnd then return nil, nil, "No MIDI editor open" end
  local take = reaper.MIDIEditor_GetTake(hwnd)
  if not take or not reaper.TakeIsMIDI(take) then
    return nil, nil, "No MIDI take in editor"
  end
  return hwnd, take, nil
end

-- Forward a keystroke to whatever it would normally do when grid mode is off.
-- Accepts a numeric command id or a named command string such as
-- "_OSARA_NEXTCHORD".
function M.passThrough(cmd)
  local hwnd = reaper.MIDIEditor_GetActive()
  local id = cmd
  if type(cmd) == "string" then id = reaper.NamedCommandLookup(cmd) end
  if not id or id == 0 then return false end
  if hwnd then
    reaper.MIDIEditor_OnCommand(hwnd, id)
  else
    reaper.Main_OnCommand(id, 0)
  end
  return true
end

----------------------------------------------------------------- note names

local PC_NAMES = { "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B" }

-- Reaper's displayed octave depends on the "midioctoffs" preference so that
-- our speech matches what OSARA and the editor say. With the default offset
-- of 1, note 60 reads as C5.
local function octaveOffset()
  if reaper.SNM_GetIntConfigVar then
    return reaper.SNM_GetIntConfigVar("midioctoffs", 1)
  end
  return 1
end

function M.noteName(pitch)
  local pc = pitch % 12
  local oct = math.floor(pitch / 12) - 1 + octaveOffset()
  return PC_NAMES[pc + 1] .. tostring(oct)
end

--------------------------------------------------------------------- scales

M.SCALES = {
  { name = "major",             steps = { 0, 2, 4, 5, 7, 9, 11 } },
  { name = "natural minor",     steps = { 0, 2, 3, 5, 7, 8, 10 } },
  { name = "harmonic minor",    steps = { 0, 2, 3, 5, 7, 8, 11 } },
  { name = "melodic minor",     steps = { 0, 2, 3, 5, 7, 9, 11 } },
  { name = "dorian",            steps = { 0, 2, 3, 5, 7, 9, 10 } },
  { name = "phrygian",          steps = { 0, 1, 3, 5, 7, 8, 10 } },
  { name = "lydian",            steps = { 0, 2, 4, 6, 7, 9, 11 } },
  { name = "mixolydian",        steps = { 0, 2, 4, 5, 7, 9, 10 } },
  { name = "locrian",           steps = { 0, 1, 3, 5, 6, 8, 10 } },
  { name = "major pentatonic",  steps = { 0, 2, 4, 7, 9 } },
  { name = "minor pentatonic",  steps = { 0, 3, 5, 7, 10 } },
  { name = "blues",             steps = { 0, 3, 5, 6, 7, 10 } },
  { name = "whole tone",        steps = { 0, 2, 4, 6, 8, 10 } },
  { name = "chromatic",         steps = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 } },
}

function M.scaleIndex()
  local n = M.getNum("scale", 1)
  if n < 1 or n > #M.SCALES then n = 1 end
  return math.floor(n)
end

function M.scaleRoot() return math.floor(M.getNum("root", 0)) % 12 end

function M.scaleName()
  return M.noteNamePc(M.scaleRoot()) .. " " .. M.SCALES[M.scaleIndex()].name
end

function M.noteNamePc(pc) return PC_NAMES[(pc % 12) + 1] end

-- Set of pitch classes belonging to the current scale.
local function scalePcSet()
  local root = M.scaleRoot()
  local set = {}
  for _, s in ipairs(M.SCALES[M.scaleIndex()].steps) do
    set[(root + s) % 12] = true
  end
  return set
end

function M.inScale(pitch) return scalePcSet()[pitch % 12] == true end

-- Step to the next pitch of the current scale in direction dir (+1 / -1).
-- Notes already off-scale simply move to the nearest scale tone in that
-- direction, so foreign notes never trap the cursor.
function M.scaleStep(pitch, dir)
  local set = scalePcSet()
  local p = pitch
  for _ = 1, 24 do
    p = p + dir
    if p < 0 or p > 127 then return nil end
    if set[p % 12] then return p end
  end
  return nil
end

------------------------------------------------------------ cursor / pitch

function M.getPitch(hwnd)
  local p = reaper.MIDIEditor_GetSetting_int(hwnd, "active_note_row")
  if not p or p < 0 or p > 127 then p = 60 end
  return p
end

function M.setPitch(hwnd, pitch)
  reaper.MIDIEditor_SetSetting_int(hwnd, "active_note_row", pitch)
end

------------------------------------------------------------------ the grid

-- Grid length in quarter notes, as configured in the MIDI editor.
function M.gridQN(take)
  local grid = reaper.MIDI_GetGrid(take)
  if not grid or grid <= 0 then grid = 1 end
  return grid
end

-- Speak grid sizes as musical fractions ("1/16", "1 bar") rather than raw
-- quarter-note counts.
function M.gridLabel(g)
  -- Length of one bar in quarter notes, at the cursor's time signature.
  local num = 4
  local ts_num, ts_den = reaper.TimeMap_GetTimeSigAtTime(0, reaper.GetCursorPosition())
  if ts_num and ts_den and ts_den > 0 then num = ts_num * (4 / ts_den) end
  if math.abs(g - num) < 1e-6 then return "1 bar" end
  if g > num then
    local bars = g / num
    return ("%g bars"):format(bars)
  end
  local frac = 4 / g
  if math.abs(frac - math.floor(frac + 0.5)) < 1e-6 then
    return ("1/%d"):format(math.floor(frac + 0.5))
  end
  return ("%.3g QN"):format(g)
end

-- The grid cell the edit cursor currently sits in.
-- Cells are aligned to the project timeline (QN 0), matching Reaper's own
-- grid lines rather than the item start.
-- Returns: startQN, endQN, cellIndex, gridQN
function M.cell(take)
  local g = M.gridQN(take)
  local qn = reaper.TimeMap2_timeToQN(0, reaper.GetCursorPosition())
  local idx = math.floor(qn / g + 1e-9)
  return idx * g, (idx + 1) * g, idx, g
end

function M.cellPPQ(take)
  local a, b = M.cell(take)
  return reaper.MIDI_GetPPQPosFromProjQN(take, a),
         reaper.MIDI_GetPPQPosFromProjQN(take, b)
end

-- Move the edit cursor to the start of cell index idx.
function M.gotoCell(take, idx)
  local g = M.gridQN(take)
  local t = reaper.TimeMap2_QNToTime(0, idx * g)
  if t < 0 then t = 0 end
  reaper.SetEditCurPos(t, true, false)
end

------------------------------------------------------------- note queries

-- A cell counts as occupied by a note if the note overlaps it at all, so
-- held notes spanning several cells register in every cell they cover.
-- The 1-tick slack keeps float rounding at cell boundaries from producing
-- phantom overlaps.
local SLACK = 1

function M.noteInCell(take, pitch, ppqA, ppqB)
  local _, notecnt = reaper.MIDI_CountEvts(take)
  for i = 0, notecnt - 1 do
    local ok, sel, muted, sppq, eppq, chan, p, vel = reaper.MIDI_GetNote(take, i)
    if ok and p == pitch and sppq < ppqB - SLACK and eppq > ppqA + SLACK then
      return i, sppq, eppq, chan, vel, sel, muted
    end
  end
  return nil
end

function M.noteEndingAt(take, pitch, ppq)
  local _, notecnt = reaper.MIDI_CountEvts(take)
  for i = 0, notecnt - 1 do
    local ok, _, _, sppq, eppq, _, p = reaper.MIDI_GetNote(take, i)
    if ok and p == pitch and math.abs(eppq - ppq) <= SLACK then return i, sppq, eppq end
  end
  return nil
end

function M.noteStartingAt(take, pitch, ppq)
  local _, notecnt = reaper.MIDI_CountEvts(take)
  for i = 0, notecnt - 1 do
    local ok, _, _, sppq, eppq, _, p = reaper.MIDI_GetNote(take, i)
    if ok and p == pitch and math.abs(sppq - ppq) <= SLACK then return i, sppq, eppq end
  end
  return nil
end

-- All pitches sounding anywhere inside the current cell, low to high.
function M.pitchesInCell(take, ppqA, ppqB)
  local out = {}
  local _, notecnt = reaper.MIDI_CountEvts(take)
  for i = 0, notecnt - 1 do
    local ok, _, muted, sppq, eppq, _, p = reaper.MIDI_GetNote(take, i)
    if ok and not muted and sppq < ppqB - SLACK and eppq > ppqA + SLACK then
      out[#out + 1] = p
    end
  end
  table.sort(out)
  -- de-duplicate unisons on different channels
  local uniq = {}
  for _, p in ipairs(out) do
    if uniq[#uniq] ~= p then uniq[#uniq + 1] = p end
  end
  return uniq
end

--------------------------------------------------------------------- edits

-- Toggle a note on/off at (current cell, pitch).
-- Returns "on", "off" or nil, plus a describing word for speech.
function M.toggleCell(take, pitch)
  local ppqA, ppqB = M.cellPPQ(take)
  local idx, sppq, eppq, chan, vel = M.noteInCell(take, pitch, ppqA, ppqB)

  reaper.Undo_BeginBlock2(0)
  local result, detail

  if idx then
    -- Cell is occupied: carve this cell out of whatever covers it.
    local startsInside = sppq >= ppqA - SLACK
    local endsInside   = eppq <= ppqB + SLACK
    if startsInside and endsInside then
      reaper.MIDI_DeleteNote(take, idx)
      detail = "removed"
    elseif startsInside then
      -- held note begins here and continues: shorten from the front
      reaper.MIDI_SetNote(take, idx, nil, nil, ppqB, nil, nil, nil, nil, true)
      detail = "shortened"
    elseif endsInside then
      -- held note ends here: shorten from the back
      reaper.MIDI_SetNote(take, idx, nil, nil, nil, ppqA, nil, nil, nil, true)
      detail = "shortened"
    else
      -- cell sits mid-way through a held note: split it in two
      reaper.MIDI_SetNote(take, idx, nil, nil, nil, ppqA, nil, nil, nil, true)
      reaper.MIDI_InsertNote(take, false, false, ppqB, eppq, chan, pitch, vel, true)
      detail = "split"
    end
    result = "off"
  else
    local v = math.floor(M.getNum("vel", 96))
    local c = math.floor(M.getNum("chan", 0))
    if M.isHold() then
      -- Join with neighbours of the same pitch so runs of adjacent cells
      -- become one sustained note rather than repeated attacks.
      local pi, _, _   = M.noteEndingAt(take, pitch, ppqA)
      local ni, nsppq, neppq = M.noteStartingAt(take, pitch, ppqB)
      if pi and ni then
        reaper.MIDI_SetNote(take, pi, nil, nil, nil, neppq, nil, nil, nil, true)
        reaper.MIDI_DeleteNote(take, ni)
        detail = "joined"
      elseif pi then
        reaper.MIDI_SetNote(take, pi, nil, nil, nil, ppqB, nil, nil, nil, true)
        detail = "extended"
      elseif ni then
        reaper.MIDI_SetNote(take, ni, nil, nil, ppqA, nil, nil, nil, nil, true)
        detail = "extended"
      else
        reaper.MIDI_InsertNote(take, false, false, ppqA, ppqB, c, pitch, v, true)
        detail = "added"
      end
    else
      reaper.MIDI_InsertNote(take, false, false, ppqA, ppqB, c, pitch, v, true)
      detail = "added"
    end
    result = "on"
  end

  reaper.MIDI_Sort(take)
  reaper.Undo_EndBlock2(0, "MIDI Grid: toggle " .. M.noteName(pitch), -1)
  return result, detail
end

--------------------------------------------------------------- note length

--[[
  Grow or shrink the note under the cursor by whole grid cells.

  This is how you sustain notes that already exist. It is deliberately
  independent of hold mode -- hold mode governs how *new* notes join as you
  enter them, whereas this edits an existing note's length in place, so it
  preserves velocity, channel and note identity. Toggling a note off and on
  again to make it join would silently reset its velocity to the default.

  Extending swallows any same-pitch notes it runs into, absorbing their tail
  if they reach further than the new end, so growing a note across repeated
  notes fuses the run rather than producing overlaps.
]]
function M.resizeNote(take, pitch, cells)
  local ppqA, ppqB = M.cellPPQ(take)
  local idx, sppq, eppq = M.noteInCell(take, pitch, ppqA, ppqB)
  if not idx then return nil end

  local g = M.gridQN(take)
  local startQN = reaper.MIDI_GetProjQNFromPPQPos(take, sppq)
  local endQN   = reaper.MIDI_GetProjQNFromPPQPos(take, eppq)

  local newEndQN = endQN + cells * g
  local clamped = false
  if newEndQN < startQN + g - 1e-9 then
    newEndQN = startQN + g -- never shrink below a single cell
    clamped = true
  end
  local newEnd = reaper.MIDI_GetPPQPosFromProjQN(take, newEndQN)

  reaper.Undo_BeginBlock2(0)

  local absorbed = 0
  if cells > 0 then
    -- Collect first, delete descending: deleting shifts later indices.
    local victims = {}
    local _, notecnt = reaper.MIDI_CountEvts(take)
    for i = 0, notecnt - 1 do
      local ok, _, _, s, e, _, p = reaper.MIDI_GetNote(take, i)
      if ok and p == pitch and i ~= idx and s > sppq + SLACK and s < newEnd - SLACK then
        victims[#victims + 1] = i
        if e > newEnd then newEnd = e end
      end
    end
    table.sort(victims, function(a, b) return a > b end)
    for _, i in ipairs(victims) do
      reaper.MIDI_DeleteNote(take, i)
      if i < idx then idx = idx - 1 end
      absorbed = absorbed + 1
    end
  end

  reaper.MIDI_SetNote(take, idx, nil, nil, nil, newEnd, nil, nil, nil, true)
  reaper.MIDI_Sort(take)
  reaper.Undo_EndBlock2(0, "MIDI Grid: resize note", -1)

  local lenCells = (reaper.MIDI_GetProjQNFromPPQPos(take, newEnd) - startQN) / g
  return math.floor(lenCells + 0.5), absorbed, clamped
end

-- Fuse every contiguous same-pitch note touching the one under the cursor
-- into a single sustained note. Returns how many notes were merged.
function M.joinRun(take, pitch)
  local ppqA, ppqB = M.cellPPQ(take)
  local idx, sppq, eppq = M.noteInCell(take, pitch, ppqA, ppqB)
  if not idx then return nil end

  local minS, maxE = sppq, eppq
  local victims = {}
  local seen = { [idx] = true }

  while true do
    local i, s = M.noteEndingAt(take, pitch, minS)
    if not i or seen[i] then break end
    seen[i] = true ; victims[#victims + 1] = i ; minS = s
  end
  while true do
    local i, _, e = M.noteStartingAt(take, pitch, maxE)
    if not i or seen[i] then break end
    seen[i] = true ; victims[#victims + 1] = i ; maxE = e
  end

  if #victims == 0 then return 0 end

  reaper.Undo_BeginBlock2(0)
  table.sort(victims, function(a, b) return a > b end)
  for _, i in ipairs(victims) do reaper.MIDI_DeleteNote(take, i) end
  -- Indices shifted; re-find the survivor by its unchanged start position.
  local keep = M.noteStartingAt(take, pitch, sppq)
  if keep then
    reaper.MIDI_SetNote(take, keep, nil, nil, minS, maxE, nil, nil, nil, true)
  end
  reaper.MIDI_Sort(take)
  reaper.Undo_EndBlock2(0, "MIDI Grid: join notes", -1)

  return #victims + 1
end

--------------------------------------------------------------------- chords

-- Stack `count` diatonic chord tones on `pitch`, skipping a scale degree
-- between each -- so in a major scale, degree 1 gives a major triad and
-- degree 2 a minor one, exactly as harmony expects. In the chromatic scale
-- this degenerates to stacked whole tones, which is arguably useless but at
-- least predictable.
function M.chordPitches(pitch, count)
  local ps = { pitch }
  local p = pitch
  for _ = 2, count do
    local a = M.scaleStep(p, 1); if not a then return nil end
    local b = M.scaleStep(a, 1); if not b then return nil end
    p = b
    ps[#ps + 1] = p
  end
  return ps
end

-- Toggle a whole chord in the current cell. If every tone is already
-- present the chord is removed; otherwise the missing tones are filled in.
-- Delegates to toggleCell so hold mode, splitting and trimming all behave
-- identically to single notes.
function M.toggleChord(take, pitches)
  local ppqA, ppqB = M.cellPPQ(take)
  local allPresent = true
  for _, p in ipairs(pitches) do
    if not M.noteInCell(take, p, ppqA, ppqB) then allPresent = false break end
  end

  reaper.Undo_BeginBlock2(0)
  local changed = {}
  for _, p in ipairs(pitches) do
    local here = M.noteInCell(take, p, ppqA, ppqB) ~= nil
    if allPresent or not here then
      M.toggleCell(take, p)
      changed[#changed + 1] = p
    end
  end
  reaper.Undo_EndBlock2(0, "MIDI Grid: toggle chord", -1)
  return (allPresent and "off" or "on"), changed
end

------------------------------------------------------------------ velocity

-- Adjust velocity by delta. If a note sits at the cursor cell and pitch, its
-- velocity changes; otherwise the default for newly inserted notes does.
-- Returns "note" or "default", and the resulting value.
function M.nudgeVelocity(take, pitch, delta)
  local ppqA, ppqB = M.cellPPQ(take)
  local idx, _, _, _, vel = M.noteInCell(take, pitch, ppqA, ppqB)
  if idx then
    local v = math.max(1, math.min(127, math.floor(vel + delta)))
    reaper.Undo_BeginBlock2(0)
    reaper.MIDI_SetNote(take, idx, nil, nil, nil, nil, nil, nil, v, true)
    reaper.MIDI_Sort(take)
    reaper.Undo_EndBlock2(0, "MIDI Grid: set velocity", -1)
    return "note", v
  end
  local v = math.max(1, math.min(127, math.floor(M.getNum("vel", 96) + delta)))
  M.set("vel", v)
  return "default", v
end

------------------------------------------------------------------ audition

--[[
  Preview is handled by a separate always-running daemon script rather than
  by deferring here. The action scripts must exit immediately: if one is
  still alive when you press the same key again, Reaper puts up its
  "script is already running" prompt, which makes fast key repeat impossible.

  So preview() only posts a request and returns. The daemon owns all
  note-on/note-off timing.
]]
function M.preview(pitches, dur)
  if not pitches or #pitches == 0 then return end
  M.setTemp("pitches", table.concat(pitches, ","))
  M.setTemp("dur", dur or M.getNum("previewdur", 0.4))
  M.setTemp("seq", (tonumber(M.getTemp("seq", "0")) or 0) + 1)
  M.ensureDaemon()
end

-- Start the preview daemon if it is not currently alive. The daemon stamps a
-- wall-clock heartbeat every cycle; anything older than a few seconds means
-- it is gone (Reaper restarted, script terminated) and we relaunch it.
function M.ensureDaemon()
  local hb = tonumber(M.getTemp("hb", "0")) or 0
  if os.time() - hb <= 3 then return end
  local id = reaper.NamedCommandLookup("_RSmidigrid_daemon")
  if id and id ~= 0 then reaper.Main_OnCommand(id, 0) end
end

--------------------------------------------------------------------- speech

-- "bar 3 beat 2" style position for the current cell.
function M.cellPosText(take)
  local a = select(1, M.cell(take))
  local t = reaper.TimeMap2_QNToTime(0, a)
  return reaper.format_timestr_pos(t, "", 2)
end

-- Describe the cell contents for speech, e.g. "C5, E5" or "empty".
function M.cellContentText(take)
  local ppqA, ppqB = M.cellPPQ(take)
  local ps = M.pitchesInCell(take, ppqA, ppqB)
  if #ps == 0 then return "empty" end
  local names = {}
  for _, p in ipairs(ps) do names[#names + 1] = M.noteName(p) end
  return table.concat(names, ", ")
end

return M