--- Locate, spawn, and wait on a `hephd` daemon. Shared by optional autostart
--- and by the e2e harness (so test readiness uses the same definition the
--- plugin does).

local uv = vim.uv or vim.loop

local M = {}

-- The daemon THIS nvim spawned (nil if we connected to an existing one).
-- `{ handle, exited = { done }, socket, db, bin }`.
M._managed = nil

--- Spawn a `local`-mode hephd against `opts.db` listening on `opts.socket`.
--- `opts.bin` defaults to `hephd` on PATH. Returns `{ handle, pid }`.
function M.spawn(opts)
  local args = { "--mode", "local" }
  if opts.db then
    table.insert(args, "--db")
    table.insert(args, opts.db)
  end
  if opts.socket then
    table.insert(args, "--socket")
    table.insert(args, opts.socket)
  end
  local handle, pid = uv.spawn(opts.bin or "hephd", {
    args = args,
    stdio = { nil, nil, opts.stderr },
  }, function(code, signal)
    if opts.on_exit then
      opts.on_exit(code, signal)
    end
  end)
  if not handle then
    error("heph: failed to spawn hephd (bin=" .. (opts.bin or "hephd") .. ")")
  end
  return { handle = handle, pid = pid }
end

--- Wait until `socket` both exists and accepts a real RPC (`health`). The
--- existence check alone races the daemon's bind→accept, so we prove liveness
--- with a round-trip. Returns `true`, or `false, reason`.
---
--- The probe runs in a **plain Lua loop**, never inside a `vim.wait` predicate:
--- the rpc round-trip itself uses `vim.wait`, and nesting `vim.wait` inside
--- another `vim.wait`'s predicate deadlocks Neovim (a stale socket made the
--- inner connect-wait re-enter and hang).
function M.wait_ready(socket, timeout)
  timeout = timeout or 5000
  local rpc = require("heph.rpc")
  local deadline = uv.hrtime() + timeout * 1e6 -- ns
  while uv.hrtime() < deadline do
    if uv.fs_stat(socket) ~= nil then
      local session = rpc.new_session(socket)
      local ok = pcall(function()
        session:call("health", vim.empty_dict(), { timeout = 200 })
      end)
      session:close()
      if ok then
        return true
      end
    end
    vim.wait(50) -- yield ~50ms; no predicate, so not nested
  end
  return false, "daemon not ready at " .. socket
end

--- Ensure a daemon is reachable at `opts.socket`. If one is already serving the
--- socket (any mode — local/server/client), connect to it and do NOT spawn. Else
--- if `opts.autostart`, spawn a local hephd we own (and manage its lifecycle).
--- Returns `reachable, spawned_by_us`.
function M.ensure(opts)
  -- Already serving? A quick probe respects a daemon someone else started.
  if M.wait_ready(opts.socket, opts.probe_ms or 400) then
    return true, false
  end
  if not opts.autostart then
    return false, false
  end
  local exited = { done = false }
  local d = M.spawn({
    bin = opts.bin,
    socket = opts.socket,
    db = opts.db,
    on_exit = function()
      exited.done = true
    end,
  })
  local ok, reason = M.wait_ready(opts.socket, opts.ready_ms or 5000)
  if not ok then
    pcall(function()
      if not d.handle:is_closing() then
        d.handle:kill("sigterm")
      end
    end)
    error("heph: spawned hephd but it never became ready: " .. tostring(reason))
  end
  M._managed = {
    handle = d.handle,
    exited = exited,
    socket = opts.socket,
    db = opts.db,
    bin = opts.bin,
  }
  return true, true
end

--- True if this nvim currently owns a live spawned daemon.
function M.is_managed()
  return M._managed ~= nil and not M._managed.exited.done
end

--- Stop the daemon this nvim spawned (no-op if we connected to an existing one).
function M.stop_spawned()
  local m = M._managed
  if not m then
    return
  end
  M._managed = nil
  if m.handle and not m.exited.done then
    pcall(function()
      m.handle:kill("sigterm")
    end)
    vim.wait(2000, function()
      return m.exited.done
    end, 20)
  end
  pcall(function()
    if m.handle and not m.handle:is_closing() then
      m.handle:close()
    end
  end)
  -- hephd doesn't unlink its socket on SIGTERM; remove it so the next launch
  -- doesn't probe a stale socket. (A crash still leaves one — wait_ready copes.)
  pcall(function()
    uv.fs_unlink(m.socket)
  end)
end

return M