---@class diffs.TreesitterConfig
---@field enabled boolean
---@field max_lines integer

---@class diffs.VimConfig
---@field enabled boolean
---@field max_lines integer

---@class diffs.IntraConfig
---@field enabled boolean
---@field algorithm string
---@field max_lines integer

---@class diffs.ContextConfig
---@field enabled boolean
---@field lines integer

---@class diffs.PrioritiesConfig
---@field clear integer
---@field syntax integer
---@field line_bg integer
---@field char_bg integer

---@class diffs.Highlights
---@field background boolean
---@field gutter boolean
---@field blend_alpha? number
---@field overrides? table<string, table>
---@field context diffs.ContextConfig
---@field treesitter diffs.TreesitterConfig
---@field vim diffs.VimConfig
---@field intra diffs.IntraConfig
---@field priorities diffs.PrioritiesConfig

---@class diffs.FugitiveConfig
---@field enabled boolean
---@field horizontal string|false
---@field vertical string|false

---@class diffs.NeogitConfig
---@field enabled boolean

---@class diffs.ConflictKeymaps
---@field ours string|false
---@field theirs string|false
---@field both string|false
---@field none string|false
---@field next string|false
---@field prev string|false

---@class diffs.ConflictConfig
---@field enabled boolean
---@field disable_diagnostics boolean
---@field show_virtual_text boolean
---@field format_virtual_text? fun(side: string, keymap: string|false): string?
---@field show_actions boolean
---@field priority integer
---@field keymaps diffs.ConflictKeymaps

---@class diffs.Config
---@field debug boolean|string
---@field hide_prefix boolean
---@field filetypes? string[] @deprecated use fugitive, neogit, extra_filetypes
---@field extra_filetypes string[]
---@field highlights diffs.Highlights
---@field fugitive diffs.FugitiveConfig
---@field neogit diffs.NeogitConfig
---@field conflict diffs.ConflictConfig

---@class diffs
---@field attach fun(bufnr?: integer)
---@field refresh fun(bufnr?: integer)
local M = {}

local highlight = require('diffs.highlight')
local log = require('diffs.log')
local parser = require('diffs.parser')

local ns = vim.api.nvim_create_namespace('diffs')

---@param hex integer
---@param bg_hex integer
---@param alpha number
---@return integer
local function blend_color(hex, bg_hex, alpha)
  ---@diagnostic disable: undefined-global
  local r = bit.band(bit.rshift(hex, 16), 0xFF)
  local g = bit.band(bit.rshift(hex, 8), 0xFF)
  local b = bit.band(hex, 0xFF)

  local bg_r = bit.band(bit.rshift(bg_hex, 16), 0xFF)
  local bg_g = bit.band(bit.rshift(bg_hex, 8), 0xFF)
  local bg_b = bit.band(bg_hex, 0xFF)

  local blend_r = math.floor(r * alpha + bg_r * (1 - alpha))
  local blend_g = math.floor(g * alpha + bg_g * (1 - alpha))
  local blend_b = math.floor(b * alpha + bg_b * (1 - alpha))

  return bit.bor(bit.lshift(blend_r, 16), bit.lshift(blend_g, 8), blend_b)
  ---@diagnostic enable: undefined-global
end

---@param name string
---@return table
local function resolve_hl(name)
  local hl = vim.api.nvim_get_hl(0, { name = name })
  while hl.link do
    hl = vim.api.nvim_get_hl(0, { name = hl.link })
  end
  return hl
end

---@type diffs.Config
local default_config = {
  debug = false,
  hide_prefix = false,
  extra_filetypes = {},
  highlights = {
    background = true,
    gutter = true,
    context = {
      enabled = true,
      lines = 25,
    },
    treesitter = {
      enabled = true,
      max_lines = 500,
    },
    vim = {
      enabled = false,
      max_lines = 200,
    },
    intra = {
      enabled = true,
      algorithm = 'default',
      max_lines = 500,
    },
    priorities = {
      clear = 198,
      syntax = 199,
      line_bg = 200,
      char_bg = 201,
    },
  },
  fugitive = {
    enabled = false,
    horizontal = 'du',
    vertical = 'dU',
  },
  neogit = {
    enabled = false,
  },
  conflict = {
    enabled = true,
    disable_diagnostics = true,
    show_virtual_text = true,
    show_actions = false,
    priority = 200,
    keymaps = {
      ours = 'doo',
      theirs = 'dot',
      both = 'dob',
      none = 'don',
      next = ']x',
      prev = '[x',
    },
  },
}

---@type diffs.Config
local config = vim.deepcopy(default_config)

local initialized = false

---@diagnostic disable-next-line: missing-fields
local fast_hl_opts = {} ---@type diffs.HunkOpts

---@type table<integer, boolean>
local attached_buffers = {}

---@type table<integer, boolean>
local diff_windows = {}

---@class diffs.HunkCacheEntry
---@field hunks diffs.Hunk[]
---@field tick integer
---@field highlighted table<integer, true>
---@field pending_clear boolean
---@field line_count integer
---@field byte_count integer

---@type table<integer, diffs.HunkCacheEntry>
local hunk_cache = {}

---@param bufnr integer
---@return boolean
function M.is_fugitive_buffer(bufnr)
  return vim.api.nvim_buf_get_name(bufnr):match('^fugitive://') ~= nil
end

---@param opts table
---@return string[]
function M.compute_filetypes(opts)
  if opts.filetypes then
    return opts.filetypes
  end
  local fts = { 'git', 'gitcommit' }
  local fug = opts.fugitive
  if fug == true or (type(fug) == 'table' and fug.enabled ~= false) then
    table.insert(fts, 'fugitive')
  end
  local neo = opts.neogit
  if neo == true or (type(neo) == 'table' and neo.enabled ~= false) then
    table.insert(fts, 'NeogitStatus')
    table.insert(fts, 'NeogitCommitView')
    table.insert(fts, 'NeogitDiffView')
  end
  if type(opts.extra_filetypes) == 'table' then
    for _, ft in ipairs(opts.extra_filetypes) do
      table.insert(fts, ft)
    end
  end
  return fts
end

local dbg = log.dbg

---@param bufnr integer
local function invalidate_cache(bufnr)
  local entry = hunk_cache[bufnr]
  if entry then
    entry.tick = -1
    entry.pending_clear = true
  end
end

---@param bufnr integer
local function ensure_cache(bufnr)
  if not vim.api.nvim_buf_is_valid(bufnr) then
    return
  end
  local tick = vim.api.nvim_buf_get_changedtick(bufnr)
  local entry = hunk_cache[bufnr]
  if entry and entry.tick == tick then
    return
  end
  if entry and not entry.pending_clear then
    local lc = vim.api.nvim_buf_line_count(bufnr)
    local bc = vim.api.nvim_buf_get_offset(bufnr, lc)
    if lc == entry.line_count and bc == entry.byte_count then
      entry.tick = tick
      entry.pending_clear = true
      dbg('content unchanged in buffer %d (tick %d), skipping reparse', bufnr, tick)
      return
    end
  end
  local hunks = parser.parse_buffer(bufnr)
  local lc = vim.api.nvim_buf_line_count(bufnr)
  local bc = vim.api.nvim_buf_get_offset(bufnr, lc)
  dbg('parsed %d hunks in buffer %d (tick %d)', #hunks, bufnr, tick)
  hunk_cache[bufnr] = {
    hunks = hunks,
    tick = tick,
    highlighted = {},
    pending_clear = true,
    line_count = lc,
    byte_count = bc,
  }

  local has_nil_ft = false
  for _, hunk in ipairs(hunks) do
    if not has_nil_ft and not hunk.ft and hunk.filename then
      has_nil_ft = true
    end
  end
  if has_nil_ft and vim.fn.did_filetype() ~= 0 then
    vim.schedule(function()
      if vim.api.nvim_buf_is_valid(bufnr) and hunk_cache[bufnr] then
        dbg('retrying filetype detection for buffer %d (was blocked by did_filetype)', bufnr)
        invalidate_cache(bufnr)
      end
    end)
  end
end

---@param hunks diffs.Hunk[]
---@param toprow integer
---@param botrow integer
---@return integer first
---@return integer last
local function find_visible_hunks(hunks, toprow, botrow)
  local n = #hunks
  if n == 0 then
    return 0, 0
  end

  local lo, hi = 1, n + 1
  while lo < hi do
    local mid = math.floor((lo + hi) / 2)
    local h = hunks[mid]
    local bottom = h.start_line - 1 + #h.lines - 1
    if bottom < toprow then
      lo = mid + 1
    else
      hi = mid
    end
  end

  if lo > n then
    return 0, 0
  end

  local first = lo
  local h = hunks[first]
  local top = (h.header_start_line and (h.header_start_line - 1)) or (h.start_line - 1)
  if top >= botrow then
    return 0, 0
  end

  local last = first
  for i = first + 1, n do
    h = hunks[i]
    top = (h.header_start_line and (h.header_start_line - 1)) or (h.start_line - 1)
    if top >= botrow then
      break
    end
    last = i
  end

  return first, last
end

local function compute_highlight_groups()
  local normal = vim.api.nvim_get_hl(0, { name = 'Normal' })
  local diff_add = vim.api.nvim_get_hl(0, { name = 'DiffAdd' })
  local diff_delete = vim.api.nvim_get_hl(0, { name = 'DiffDelete' })
  local diff_added = resolve_hl('diffAdded')
  local diff_removed = resolve_hl('diffRemoved')

  local bg = normal.bg or 0x1e1e2e
  local add_bg = diff_add.bg or 0x2e4a3a
  local del_bg = diff_delete.bg or 0x4a2e3a
  local add_fg = diff_added.fg or diff_add.fg or 0x80c080
  local del_fg = diff_removed.fg or diff_delete.fg or 0xc08080

  local blended_add = blend_color(add_bg, bg, 0.4)
  local blended_del = blend_color(del_bg, bg, 0.4)

  local alpha = config.highlights.blend_alpha or 0.6
  local blended_add_text = blend_color(add_fg, bg, alpha)
  local blended_del_text = blend_color(del_fg, bg, alpha)

  vim.api.nvim_set_hl(0, 'DiffsClear', { default = true, fg = normal.fg or 0xc0c0c0 })
  vim.api.nvim_set_hl(0, 'DiffsAdd', { default = true, bg = blended_add })
  vim.api.nvim_set_hl(0, 'DiffsDelete', { default = true, bg = blended_del })
  vim.api.nvim_set_hl(0, 'DiffsAddNr', { default = true, fg = blended_add_text, bg = blended_add })
  vim.api.nvim_set_hl(
    0,
    'DiffsDeleteNr',
    { default = true, fg = blended_del_text, bg = blended_del }
  )
  vim.api.nvim_set_hl(0, 'DiffsAddText', { default = true, bg = blended_add_text })
  vim.api.nvim_set_hl(0, 'DiffsDeleteText', { default = true, bg = blended_del_text })

  dbg('highlight groups: Normal.bg=#%06x DiffAdd.bg=#%06x diffAdded.fg=#%06x', bg, add_bg, add_fg)
  dbg(
    'DiffsAdd.bg=#%06x DiffsAddText.bg=#%06x DiffsAddNr.fg=#%06x',
    blended_add,
    blended_add_text,
    add_fg
  )
  dbg('DiffsDelete.bg=#%06x DiffsDeleteText.bg=#%06x', blended_del, blended_del_text)

  local diff_change = resolve_hl('DiffChange')
  local diff_text = resolve_hl('DiffText')

  vim.api.nvim_set_hl(0, 'DiffsDiffAdd', { default = true, bg = diff_add.bg })
  vim.api.nvim_set_hl(
    0,
    'DiffsDiffDelete',
    { default = true, fg = diff_delete.fg, bg = diff_delete.bg }
  )
  vim.api.nvim_set_hl(0, 'DiffsDiffChange', { default = true, bg = diff_change.bg })
  vim.api.nvim_set_hl(0, 'DiffsDiffText', { default = true, bg = diff_text.bg })

  local change_bg = diff_change.bg or 0x3a3a4a
  local text_bg = diff_text.bg or 0x4a4a5a
  local change_fg = diff_change.fg or diff_text.fg or 0x80a0c0

  local blended_ours = blend_color(add_bg, bg, 0.4)
  local blended_theirs = blend_color(change_bg, bg, 0.4)
  local blended_base = blend_color(text_bg, bg, 0.3)
  local blended_ours_nr = blend_color(add_fg, bg, alpha)
  local blended_theirs_nr = blend_color(change_fg, bg, alpha)
  local blended_base_nr = blend_color(change_fg, bg, 0.4)

  vim.api.nvim_set_hl(0, 'DiffsConflictOurs', { default = true, bg = blended_ours })
  vim.api.nvim_set_hl(0, 'DiffsConflictTheirs', { default = true, bg = blended_theirs })
  vim.api.nvim_set_hl(0, 'DiffsConflictBase', { default = true, bg = blended_base })
  vim.api.nvim_set_hl(0, 'DiffsConflictMarker', { default = true, fg = 0x808080, bold = true })
  vim.api.nvim_set_hl(0, 'DiffsConflictActions', { default = true, fg = 0x808080 })
  vim.api.nvim_set_hl(
    0,
    'DiffsConflictOursNr',
    { default = true, fg = blended_ours_nr, bg = blended_ours }
  )
  vim.api.nvim_set_hl(
    0,
    'DiffsConflictTheirsNr',
    { default = true, fg = blended_theirs_nr, bg = blended_theirs }
  )
  vim.api.nvim_set_hl(
    0,
    'DiffsConflictBaseNr',
    { default = true, fg = blended_base_nr, bg = blended_base }
  )

  if config.highlights.overrides then
    for group, hl in pairs(config.highlights.overrides) do
      vim.api.nvim_set_hl(0, group, hl)
    end
  end
end

local neogit_attached = false

local neogit_hl_groups = {
  'NeogitDiffAdd',
  'NeogitDiffAddCursor',
  'NeogitDiffAddHighlight',
  'NeogitDiffDelete',
  'NeogitDiffDeleteCursor',
  'NeogitDiffDeleteHighlight',
  'NeogitDiffContext',
  'NeogitDiffContextCursor',
  'NeogitDiffContextHighlight',
  'NeogitDiffHeader',
  'NeogitDiffHeaderHighlight',
  'NeogitHunkHeader',
  'NeogitHunkHeaderCursor',
  'NeogitHunkHeaderHighlight',
  'NeogitHunkMergeHeader',
  'NeogitHunkMergeHeaderCursor',
  'NeogitHunkMergeHeaderHighlight',
}

local function override_neogit_highlights()
  for _, name in ipairs(neogit_hl_groups) do
    vim.api.nvim_set_hl(0, name, {})
  end
end

local function init()
  if initialized then
    return
  end
  initialized = true

  local opts = vim.g.diffs or {}

  if opts.filetypes then
    vim.deprecate(
      'vim.g.diffs.filetypes',
      'fugitive, neogit, and extra_filetypes',
      '0.3.0',
      'diffs.nvim'
    )
  end

  if not opts.filetypes and opts.fugitive == nil and opts.neogit == nil then
    local has_diff_ft = false
    if type(opts.extra_filetypes) == 'table' then
      for _, ft in ipairs(opts.extra_filetypes) do
        if ft == 'diff' then
          has_diff_ft = true
          break
        end
      end
    end
    if not has_diff_ft then
      vim.notify(
        '[diffs.nvim] fugitive, neogit, and diff filetypes are now opt-in.\n'
          .. 'Add the integrations you use to your config:\n\n'
          .. '  vim.g.diffs = {\n'
          .. '    fugitive = true,\n'
          .. '    neogit = true,\n'
          .. "    extra_filetypes = { 'diff' },\n"
          .. '  }\n\n'
          .. 'This warning will be removed in 0.3.0.',
        vim.log.levels.WARN
      )
    end
  end

  if opts.fugitive == true then
    opts.fugitive = { enabled = true }
  elseif opts.fugitive == false then
    opts.fugitive = { enabled = false }
  elseif opts.fugitive == nil then
    opts.fugitive = nil
  elseif type(opts.fugitive) == 'table' and opts.fugitive.enabled == nil then
    opts.fugitive.enabled = true
  end

  if opts.neogit == true then
    opts.neogit = { enabled = true }
  elseif opts.neogit == false then
    opts.neogit = { enabled = false }
  elseif opts.neogit == nil then
    opts.neogit = nil
  elseif type(opts.neogit) == 'table' and opts.neogit.enabled == nil then
    opts.neogit.enabled = true
  end

  vim.validate({
    debug = {
      opts.debug,
      function(v)
        return v == nil or type(v) == 'boolean' or type(v) == 'string'
      end,
      'boolean or string (file path)',
    },
    hide_prefix = { opts.hide_prefix, 'boolean', true },
    fugitive = { opts.fugitive, 'table', true },
    neogit = { opts.neogit, 'table', true },
    extra_filetypes = { opts.extra_filetypes, 'table', true },
    highlights = { opts.highlights, 'table', true },
  })

  if opts.highlights then
    vim.validate({
      ['highlights.background'] = { opts.highlights.background, 'boolean', true },
      ['highlights.gutter'] = { opts.highlights.gutter, 'boolean', true },
      ['highlights.blend_alpha'] = { opts.highlights.blend_alpha, 'number', true },
      ['highlights.overrides'] = { opts.highlights.overrides, 'table', true },
      ['highlights.context'] = { opts.highlights.context, 'table', true },
      ['highlights.treesitter'] = { opts.highlights.treesitter, 'table', true },
      ['highlights.vim'] = { opts.highlights.vim, 'table', true },
      ['highlights.intra'] = { opts.highlights.intra, 'table', true },
      ['highlights.priorities'] = { opts.highlights.priorities, 'table', true },
    })

    if opts.highlights.context then
      vim.validate({
        ['highlights.context.enabled'] = { opts.highlights.context.enabled, 'boolean', true },
        ['highlights.context.lines'] = { opts.highlights.context.lines, 'number', true },
      })
    end

    if opts.highlights.treesitter then
      vim.validate({
        ['highlights.treesitter.enabled'] = { opts.highlights.treesitter.enabled, 'boolean', true },
        ['highlights.treesitter.max_lines'] = {
          opts.highlights.treesitter.max_lines,
          'number',
          true,
        },
      })
    end

    if opts.highlights.vim then
      vim.validate({
        ['highlights.vim.enabled'] = { opts.highlights.vim.enabled, 'boolean', true },
        ['highlights.vim.max_lines'] = { opts.highlights.vim.max_lines, 'number', true },
      })
    end

    if opts.highlights.intra then
      vim.validate({
        ['highlights.intra.enabled'] = { opts.highlights.intra.enabled, 'boolean', true },
        ['highlights.intra.algorithm'] = {
          opts.highlights.intra.algorithm,
          function(v)
            return v == nil or v == 'default' or v == 'vscode'
          end,
          "'default' or 'vscode'",
        },
        ['highlights.intra.max_lines'] = { opts.highlights.intra.max_lines, 'number', true },
      })
    end

    if opts.highlights.priorities then
      vim.validate({
        ['highlights.priorities.clear'] = { opts.highlights.priorities.clear, 'number', true },
        ['highlights.priorities.syntax'] = { opts.highlights.priorities.syntax, 'number', true },
        ['highlights.priorities.line_bg'] = { opts.highlights.priorities.line_bg, 'number', true },
        ['highlights.priorities.char_bg'] = { opts.highlights.priorities.char_bg, 'number', true },
      })
    end
  end

  if opts.fugitive then
    vim.validate({
      ['fugitive.enabled'] = { opts.fugitive.enabled, 'boolean', true },
      ['fugitive.horizontal'] = {
        opts.fugitive.horizontal,
        function(v)
          return v == nil or v == false or type(v) == 'string'
        end,
        'string or false',
      },
      ['fugitive.vertical'] = {
        opts.fugitive.vertical,
        function(v)
          return v == nil or v == false or type(v) == 'string'
        end,
        'string or false',
      },
    })
  end

  if opts.neogit then
    vim.validate({
      ['neogit.enabled'] = { opts.neogit.enabled, 'boolean', true },
    })
  end

  if opts.conflict then
    vim.validate({
      ['conflict.enabled'] = { opts.conflict.enabled, 'boolean', true },
      ['conflict.disable_diagnostics'] = { opts.conflict.disable_diagnostics, 'boolean', true },
      ['conflict.show_virtual_text'] = { opts.conflict.show_virtual_text, 'boolean', true },
      ['conflict.format_virtual_text'] = { opts.conflict.format_virtual_text, 'function', true },
      ['conflict.show_actions'] = { opts.conflict.show_actions, 'boolean', true },
      ['conflict.priority'] = { opts.conflict.priority, 'number', true },
      ['conflict.keymaps'] = { opts.conflict.keymaps, 'table', true },
    })

    if opts.conflict.keymaps then
      local keymap_validator = function(v)
        return v == false or type(v) == 'string'
      end
      for _, key in ipairs({ 'ours', 'theirs', 'both', 'none', 'next', 'prev' }) do
        vim.validate({
          ['conflict.keymaps.' .. key] = {
            opts.conflict.keymaps[key],
            keymap_validator,
            'string or false',
          },
        })
      end
    end
  end

  if
    opts.highlights
    and opts.highlights.context
    and opts.highlights.context.lines
    and opts.highlights.context.lines < 0
  then
    error('diffs: highlights.context.lines must be >= 0')
  end
  if
    opts.highlights
    and opts.highlights.treesitter
    and opts.highlights.treesitter.max_lines
    and opts.highlights.treesitter.max_lines < 1
  then
    error('diffs: highlights.treesitter.max_lines must be >= 1')
  end
  if
    opts.highlights
    and opts.highlights.vim
    and opts.highlights.vim.max_lines
    and opts.highlights.vim.max_lines < 1
  then
    error('diffs: highlights.vim.max_lines must be >= 1')
  end
  if
    opts.highlights
    and opts.highlights.intra
    and opts.highlights.intra.max_lines
    and opts.highlights.intra.max_lines < 1
  then
    error('diffs: highlights.intra.max_lines must be >= 1')
  end
  if
    opts.highlights
    and opts.highlights.blend_alpha
    and (opts.highlights.blend_alpha < 0 or opts.highlights.blend_alpha > 1)
  then
    error('diffs: highlights.blend_alpha must be >= 0 and <= 1')
  end
  if opts.highlights and opts.highlights.priorities then
    for _, key in ipairs({ 'clear', 'syntax', 'line_bg', 'char_bg' }) do
      local v = opts.highlights.priorities[key]
      if v and v < 0 then
        error('diffs: highlights.priorities.' .. key .. ' must be >= 0')
      end
    end
  end
  if opts.conflict and opts.conflict.priority and opts.conflict.priority < 0 then
    error('diffs: conflict.priority must be >= 0')
  end

  config = vim.tbl_deep_extend('force', default_config, opts)
  log.set_enabled(config.debug)

  fast_hl_opts = {
    hide_prefix = config.hide_prefix,
    highlights = vim.tbl_deep_extend('force', config.highlights, {
      treesitter = { enabled = false },
    }),
    defer_vim_syntax = true,
  }

  compute_highlight_groups()

  vim.api.nvim_create_autocmd('ColorScheme', {
    callback = function()
      compute_highlight_groups()
      if neogit_attached then
        vim.schedule(override_neogit_highlights)
      end
      for bufnr, _ in pairs(attached_buffers) do
        invalidate_cache(bufnr)
      end
    end,
  })

  vim.api.nvim_set_decoration_provider(ns, {
    on_buf = function(_, bufnr)
      if not attached_buffers[bufnr] then
        return false
      end
      local t0 = config.debug and vim.uv.hrtime() or nil
      ensure_cache(bufnr)
      local entry = hunk_cache[bufnr]
      if entry and entry.pending_clear then
        vim.api.nvim_buf_clear_namespace(bufnr, ns, 0, -1)
        entry.highlighted = {}
        entry.pending_clear = false
      end
      if t0 then
        dbg('on_buf %d: %.2fms', bufnr, (vim.uv.hrtime() - t0) / 1e6)
      end
    end,
    on_win = function(_, _, bufnr, toprow, botrow)
      if not attached_buffers[bufnr] then
        return false
      end
      local entry = hunk_cache[bufnr]
      if not entry then
        return
      end
      local first, last = find_visible_hunks(entry.hunks, toprow, botrow)
      if first == 0 then
        return
      end
      local t0 = config.debug and vim.uv.hrtime() or nil
      local deferred_syntax = {}
      local count = 0
      for i = first, last do
        if not entry.highlighted[i] then
          local hunk = entry.hunks[i]
          highlight.highlight_hunk(bufnr, ns, hunk, fast_hl_opts)
          entry.highlighted[i] = true
          count = count + 1
          local has_syntax = hunk.lang and config.highlights.treesitter.enabled
          local needs_vim = not hunk.lang and hunk.ft and config.highlights.vim.enabled
          if has_syntax or needs_vim then
            table.insert(deferred_syntax, hunk)
          end
        end
      end
      if #deferred_syntax > 0 then
        local tick = entry.tick
        vim.schedule(function()
          if not vim.api.nvim_buf_is_valid(bufnr) then
            return
          end
          local cur = hunk_cache[bufnr]
          if not cur or cur.tick ~= tick then
            return
          end
          local t1 = config.debug and vim.uv.hrtime() or nil
          local full_opts = {
            hide_prefix = config.hide_prefix,
            highlights = config.highlights,
          }
          for _, hunk in ipairs(deferred_syntax) do
            local start_row = hunk.start_line - 1
            local end_row = start_row + #hunk.lines
            if hunk.header_start_line then
              start_row = hunk.header_start_line - 1
            end
            vim.api.nvim_buf_clear_namespace(bufnr, ns, start_row, end_row)
            highlight.highlight_hunk(bufnr, ns, hunk, full_opts)
            if not hunk.lang and hunk.ft then
              highlight.highlight_hunk_vim_syntax(bufnr, ns, hunk, full_opts)
            end
          end
          if t1 then
            dbg('deferred pass: %d hunks in %.2fms', #deferred_syntax, (vim.uv.hrtime() - t1) / 1e6)
          end
        end)
      end
      if t0 and count > 0 then
        dbg(
          'on_win %d: %d hunks [%d..%d] in %.2fms (viewport %d-%d)',
          bufnr,
          count,
          first,
          last,
          (vim.uv.hrtime() - t0) / 1e6,
          toprow,
          botrow
        )
      end
    end,
  })

  vim.api.nvim_create_autocmd('WinClosed', {
    callback = function(args)
      local win = tonumber(args.match)
      if win and diff_windows[win] then
        diff_windows[win] = nil
      end
    end,
  })
end

---@param bufnr? integer
function M.attach(bufnr)
  init()
  bufnr = bufnr or vim.api.nvim_get_current_buf()

  if attached_buffers[bufnr] then
    return
  end
  attached_buffers[bufnr] = true

  if not neogit_attached and config.neogit.enabled and vim.bo[bufnr].filetype:match('^Neogit') then
    neogit_attached = true
    vim.schedule(override_neogit_highlights)
  end

  dbg('attaching to buffer %d', bufnr)

  ensure_cache(bufnr)

  vim.api.nvim_create_autocmd('BufWipeout', {
    buffer = bufnr,
    callback = function()
      attached_buffers[bufnr] = nil
      hunk_cache[bufnr] = nil
    end,
  })
end

---@param bufnr? integer
function M.refresh(bufnr)
  bufnr = bufnr or vim.api.nvim_get_current_buf()
  invalidate_cache(bufnr)
end

local DIFF_WINHIGHLIGHT = table.concat({
  'DiffAdd:DiffsDiffAdd',
  'DiffDelete:DiffsDiffDelete',
  'DiffChange:DiffsDiffChange',
  'DiffText:DiffsDiffText',
}, ',')

function M.attach_diff()
  init()
  local tabpage = vim.api.nvim_get_current_tabpage()
  local wins = vim.api.nvim_tabpage_list_wins(tabpage)

  local diff_wins = {}

  for _, win in ipairs(wins) do
    if vim.api.nvim_win_is_valid(win) and vim.wo[win].diff then
      table.insert(diff_wins, win)
    end
  end

  if #diff_wins == 0 then
    return
  end

  for _, win in ipairs(diff_wins) do
    vim.api.nvim_set_option_value('winhighlight', DIFF_WINHIGHLIGHT, { win = win })
    diff_windows[win] = true
    dbg('applied diff winhighlight to window %d', win)
  end
end

function M.detach_diff()
  for win, _ in pairs(diff_windows) do
    if vim.api.nvim_win_is_valid(win) then
      vim.api.nvim_set_option_value('winhighlight', '', { win = win })
    end
    diff_windows[win] = nil
  end
end

---@return diffs.FugitiveConfig
function M.get_fugitive_config()
  init()
  return config.fugitive
end

---@return diffs.ConflictConfig
function M.get_conflict_config()
  init()
  return config.conflict
end

M._test = {
  find_visible_hunks = find_visible_hunks,
  hunk_cache = hunk_cache,
  ensure_cache = ensure_cache,
  invalidate_cache = invalidate_cache,
}

return M