local M = {}

local diagnostic = require('preview.diagnostic')
local log = require('preview.log')

---@type table<integer, preview.Process>
local active = {}

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

---@type table<integer, true>
local opened = {}

---@param val string[]|fun(ctx: preview.Context): string[]
---@param ctx preview.Context
---@return string[]
local function eval_list(val, ctx)
  if type(val) == 'function' then
    return val(ctx)
  end
  return val
end

---@param val string|fun(ctx: preview.Context): string
---@param ctx preview.Context
---@return string
local function eval_string(val, ctx)
  if type(val) == 'function' then
    return val(ctx)
  end
  return val
end

---@param bufnr integer
---@param name string
---@param provider preview.ProviderConfig
---@param ctx preview.Context
function M.compile(bufnr, name, provider, ctx)
  if vim.bo[bufnr].modified then
    vim.cmd('silent! update')
  end

  if active[bufnr] then
    log.dbg('killing existing process for buffer %d before recompile', bufnr)
    M.stop(bufnr)
  end

  local cmd = vim.list_extend({}, provider.cmd)
  if provider.args then
    vim.list_extend(cmd, eval_list(provider.args, ctx))
  end

  local cwd = ctx.root
  if provider.cwd then
    cwd = eval_string(provider.cwd, ctx)
  end

  local output_file = ''
  if provider.output then
    output_file = eval_string(provider.output, ctx)
  end

  log.dbg('compiling buffer %d with provider "%s": %s', bufnr, name, table.concat(cmd, ' '))

  local obj = vim.system(
    cmd,
    {
      cwd = cwd,
      env = provider.env,
    },
    vim.schedule_wrap(function(result)
      active[bufnr] = nil
      if not vim.api.nvim_buf_is_valid(bufnr) then
        return
      end

      if result.code == 0 then
        log.dbg('compilation succeeded for buffer %d', bufnr)
        diagnostic.clear(bufnr)
        vim.api.nvim_exec_autocmds('User', {
          pattern = 'PreviewCompileSuccess',
          data = { bufnr = bufnr, provider = name, output = output_file },
        })
        if provider.open and not opened[bufnr] and output_file ~= '' then
          if provider.open == true then
            vim.ui.open(output_file)
          elseif type(provider.open) == 'table' then
            local open_cmd = vim.list_extend({}, provider.open)
            table.insert(open_cmd, output_file)
            vim.system(open_cmd)
          end
          opened[bufnr] = true
        end
      else
        log.dbg('compilation failed for buffer %d (exit code %d)', bufnr, result.code)
        if provider.error_parser then
          diagnostic.set(bufnr, name, provider.error_parser, result.stderr or '', ctx)
        end
        vim.api.nvim_exec_autocmds('User', {
          pattern = 'PreviewCompileFailed',
          data = {
            bufnr = bufnr,
            provider = name,
            code = result.code,
            stderr = result.stderr or '',
          },
        })
      end
    end)
  )

  active[bufnr] = { obj = obj, provider = name, output_file = output_file }

  vim.api.nvim_create_autocmd('BufWipeout', {
    buffer = bufnr,
    once = true,
    callback = function()
      M.stop(bufnr)
    end,
  })

  vim.api.nvim_exec_autocmds('User', {
    pattern = 'PreviewCompileStarted',
    data = { bufnr = bufnr, provider = name },
  })
end

---@param bufnr integer
function M.stop(bufnr)
  local proc = active[bufnr]
  if not proc then
    return
  end
  log.dbg('stopping process for buffer %d', bufnr)
  ---@type fun(self: table, signal: string|integer)
  local kill = proc.obj.kill
  kill(proc.obj, 'sigterm')

  local timer = vim.uv.new_timer()
  if timer then
    timer:start(5000, 0, function()
      timer:close()
      if active[bufnr] and active[bufnr].obj == proc.obj then
        kill(proc.obj, 'sigkill')
        active[bufnr] = nil
      end
    end)
  end
end

function M.stop_all()
  for bufnr, _ in pairs(active) do
    M.stop(bufnr)
  end
  for bufnr, _ in pairs(watching) do
    M.unwatch(bufnr)
  end
end

---@param bufnr integer
---@param name string
---@param provider preview.ProviderConfig
---@param ctx_builder fun(bufnr: integer): preview.Context
function M.toggle(bufnr, name, provider, ctx_builder)
  if watching[bufnr] then
    M.unwatch(bufnr)
    return
  end

  local au_id = vim.api.nvim_create_autocmd('BufWritePost', {
    buffer = bufnr,
    callback = function()
      local ctx = ctx_builder(bufnr)
      M.compile(bufnr, name, provider, ctx)
    end,
  })

  watching[bufnr] = au_id
  log.dbg('watching buffer %d with provider "%s"', bufnr, name)

  vim.api.nvim_create_autocmd('BufWipeout', {
    buffer = bufnr,
    once = true,
    callback = function()
      M.unwatch(bufnr)
      opened[bufnr] = nil
    end,
  })

  vim.api.nvim_exec_autocmds('User', {
    pattern = 'PreviewWatchStarted',
    data = { bufnr = bufnr, provider = name },
  })

  M.compile(bufnr, name, provider, ctx_builder(bufnr))
end

---@param bufnr integer
function M.unwatch(bufnr)
  local au_id = watching[bufnr]
  if not au_id then
    return
  end
  vim.api.nvim_del_autocmd(au_id)
  watching[bufnr] = nil
  log.dbg('unwatched buffer %d', bufnr)

  vim.api.nvim_exec_autocmds('User', {
    pattern = 'PreviewWatchStopped',
    data = { bufnr = bufnr },
  })
end

---@param bufnr integer
---@param name string
---@param provider preview.ProviderConfig
---@param ctx preview.Context
function M.clean(bufnr, name, provider, ctx)
  if not provider.clean then
    vim.notify('[preview.nvim] provider "' .. name .. '" has no clean command', vim.log.levels.WARN)
    return
  end

  local cmd = eval_list(provider.clean, ctx)
  local cwd = ctx.root
  if provider.cwd then
    cwd = eval_string(provider.cwd, ctx)
  end

  log.dbg('cleaning buffer %d with provider "%s": %s', bufnr, name, table.concat(cmd, ' '))

  vim.system(
    cmd,
    { cwd = cwd },
    vim.schedule_wrap(function(result)
      if result.code == 0 then
        log.dbg('clean succeeded for buffer %d', bufnr)
        vim.notify('[preview.nvim] clean complete', vim.log.levels.INFO)
      else
        log.dbg('clean failed for buffer %d (exit code %d)', bufnr, result.code)
        vim.notify('[preview.nvim] clean failed: ' .. (result.stderr or ''), vim.log.levels.ERROR)
      end
    end)
  )
end

---@param bufnr integer
---@return preview.Status
function M.status(bufnr)
  local proc = active[bufnr]
  if proc then
    return {
      compiling = true,
      watching = watching[bufnr] ~= nil,
      provider = proc.provider,
      output_file = proc.output_file,
    }
  end
  return { compiling = false, watching = watching[bufnr] ~= nil }
end

M._test = {
  active = active,
  watching = watching,
  opened = opened,
}

return M