-------------------------------------------------------------------------------
-- Copyright (c) 2011-2012 Sierra Wireless and others.
-- All rights reserved. This program and the accompanying materials
-- are made available under the terms of the Eclipse Public License v1.0
-- which accompanies this distribution, and is available at
-- http://www.eclipse.org/legal/epl-v10.html
--
-- Contributors:
--     Sierra Wireless - initial API and implementation
-------------------------------------------------------------------------------

local DBGP_CLIENT_VERSION = "1.4.0"
DBGP_CLIENT_LUA_VERSION = os.getenv "LUA_VERSION" or _VERSION
if DBGP_CLIENT_LUA_VERSION ~= "Lua 5.1" and DBGP_CLIENT_LUA_VERSION ~= "Lua 5.2" then
  print(DBGP_CLIENT_LUA_VERSION .. " is not supported. As fallback, debugger will behave as if it runs on Lua 5.2 vm. You could also try to force it to behave as a Lua 5.1 vm by setting the LUA_VERSION environment variable to 'Lua 5.1'")
  DBGP_CLIENT_LUA_VERSION = "Lua 5.2"
end

local debug = require "debug"

-- To avoid cyclic dependency, internal state of the debugger that must be accessed
-- elsewhere (in commands most likely) will be stored in a fake module "debugger.core"
local core = { }
package.loaded["debugger.core"] = core

local util = require "debugger.util"
local platform = require "debugger.platform"
local dbgp = require "debugger.dbgp"
local commands = require "debugger.commands"
local context = require "debugger.context"
local url = require "debugger.url"

local log = util.log


-- TODO complete the stdlib access
local corunning, cocreate, cowrap, coyield, coresume, costatus = coroutine.running, coroutine.create, coroutine.wrap, coroutine.yield, coroutine.resume, coroutine.status


-- register the URI of the debugger, to not jump into with redefined function or coroutine bootstrap stuff
local debugger_uri = nil -- set in init function
local transportmodule_uri = nil -- set in init function

-- will contain the session object, and possibly a list of all sessions if a multi-threaded model is adopted
-- this is only used for async commands.
local active_session = nil

-- tracks all active coroutines and associate an id to them, the table from_id is the id=>coro mapping, the table from_coro is the reverse
core.active_coroutines = { n = 0, from_id = setmetatable({ }, { __mode = "v" }), from_coro = setmetatable({ }, { __mode = "k" }) }

-- "BEGIN VERSION DEPENDENT CODE"
local setbpenv     -- set environment of a breakpoint (compiled function)
if DBGP_CLIENT_LUA_VERSION == "Lua 5.1" then
  local setfenv = setfenv
  setbpenv = setfenv
elseif DBGP_CLIENT_LUA_VERSION == "Lua 5.2" then
  local setupvalue = debug.setupvalue
  -- _ENV is the first upvalue
  setbpenv = function(f, t) return setupvalue(f, 1, t) end
end
-- "END VERSION DEPENDENT CODE"

-------------------------------------------------------------------------------
--  Output redirection handling
-------------------------------------------------------------------------------
-- Override standard output functions & constants to redirect data written to these files to IDE too.
-- This works only for output done in Lua, output written by C extensions is still go to system output file.

-- references to native values
io.base = { output = io.output, stdin = io.stdin, stdout = io.stdout, stderr = io.stderr }

function print(...)
  local buf = {...}
  for i=1, select("#", ...) do
    buf[i] = tostring(buf[i])
  end
  io.stdout:write(table.concat(buf, "\t") .. "\n")
end

-- Actually change standard output file but still return the "fake" stdout
function io.output(output)
  io.base.output(output)
  return io.stdout
end

local dummy = function() end

-- metatable for redirecting output (not printed at all in actual output)
core.redirect_output = {
  write = function(self, ...)
    local buf = {...}
    for i=1, select("#", ...) do buf[i] = tostring(buf[i]) end
    buf = table.concat(buf):gsub("\n", "\r\n")
    dbgp.send_xml(self.skt, { tag = "stream", attr = { type=self.mode },  util.b64(buf) } )
  end,
  flush = dummy,
  close = dummy,
  setvbuf = dummy,
  seek = dummy
}
core.redirect_output.__index = core.redirect_output

-- metatable for cloning output (outputs to actual system and send to IDE)
core.copy_output = {
  write = function(self, ...)
    core.redirect_output.write(self, ...)
    io.base[self.mode]:write(...)
  end,
  flush   = function(self, ...) return self.out:flush(...) end,
  close   = function(self, ...) return self.out:close(...) end,
  setvbuf = function(self, ...) return self.out:setvbuf(...) end,
  seek    = function(self, ...) return self.out:seek(...) end,
}
core.copy_output.__index = core.copy_output

-------------------------------------------------------------------------------
--  Breakpoint registry
-------------------------------------------------------------------------------
-- Registry of current stack levels of all running threads
local stack_levels = setmetatable( { }, { __mode = "k" } )

-- File/line mapping for breakpoints (BP). For a given file/line, a list of BP is associated (DBGp specification section 7.6.1
-- require that multiple BP at same place must be handled)
-- A BP is a table with all additional properties (type, condition, ...) the id is the string representation of the table.
core.breakpoints = {
  -- functions to call to match hit conditions
  hit_conditions = {
    [">="] = function(value, target) return value >= target end,
    ["=="] = function(value, target) return value == target end,
    ["%"]  = function(value, target) return (value % target) == 0 end,
  }
}

-- tracks events such as step_into or step_over
core.events = { }

do
  local file_mapping = { }
  local id_mapping = { }
  local waiting_sessions = { } -- sessions that wait for an event (over, into, out)
  local step_into = nil        -- session that registered a step_into event, if any
  local sequence = 0 -- used to generate breakpoint IDs

  --- Inserts a new breakpoint into registry
  -- @param bp (table) breakpoint data
  -- @param uri (string, optional) Absolute file URI, for line breakpoints
  -- @param line (number, optional) Line where breakpoint stops, for line breakpoints
  -- @return breakpoint identifier
  function core.breakpoints.insert(bp)
    local bpid = sequence
    sequence = bpid + 1
    bp.id = bpid
    -- re-encode the URI to avoid any mismatch (with authority for example)
    local uri = url.parse(bp.filename)
    bp.filename = url.build{ scheme=uri.scheme, authority="", path=platform.normalize(uri.path)}

    local filereg = file_mapping[bp.filename]
    if not filereg then
      filereg = { }
      file_mapping[bp.filename] = filereg
    end

    local linereg = filereg[bp.lineno]
    if not linereg then
      linereg = {}
      filereg[bp.lineno] = linereg
    end

    table.insert(linereg, bp)

    id_mapping[bpid] = bp
    return bpid
  end

  --- If breakpoint(s) exists for given file/line, uptates breakpoint counters
  -- and returns whether a breakpoint has matched (boolean)
  function core.breakpoints.at(file, line)
    local bps = file_mapping[file] and file_mapping[file][line]
    if not bps then return nil end

    local do_break = false
    for _, bp in pairs(bps) do
      if bp.state == "enabled" then
        local match = true
        if bp.condition then
          -- TODO: this is not the optimal solution because Context can be instantiated twice if the breakpoint matches
          local cxt = context.Context:new(active_session.coro, 0)
          setbpenv(bp.condition, cxt)
          local success, result = pcall(bp.condition)
          if not success then log("ERROR", "Condition evaluation failed for breakpoint at %s:%d: %s", file, line, result) end
          -- debugger always stops if an error occurs
          match = (not success) or result
        end
        if match then
          bp.hit_count = bp.hit_count + 1
          if core.breakpoints.hit_conditions[bp.hit_condition](bp.hit_count, bp.hit_value) then
            if bp.temporary then
              core.breakpoints.remove(bp.id)
            end
            do_break = true
            -- there is no break to handle multiple breakpoints: all hit counts must be updated
          end
        end
      end
    end
    return do_break
  end

  function core.breakpoints.get(id)
    if id then return id_mapping[id]
    else return id_mapping end
  end

  function core.breakpoints.remove(id)
    local bp = id_mapping[id]
    if bp then
      id_mapping[id] = nil
      local linereg = file_mapping[bp.filename][bp.lineno]
      for i=1, #linereg do
        if linereg[i] == bp then
          table.remove(linereg, i)
          break
        end
      end

      -- cleanup file_mapping
      if not next(linereg) then file_mapping[bp.filename][bp.lineno] = nil end
      if not next(file_mapping[bp.filename]) then file_mapping[bp.filename] = nil end
      return true
    end
    return false
  end

  --- Returns an XML data structure that describes given breakpoint
  -- @param id (number) breakpoint ID
  -- @return Table describing a <breakpooint> tag or nil followed by an error message
  function core.breakpoints.get_xml(id)
    local bp = id_mapping[id]
    if not bp then return nil, "No such breakpoint: "..tostring(id) end

    local response = { tag = "breakpoint", attr = { } }
    for k,v in pairs(bp) do response.attr[k] = v end
    if bp.expression then
      response[1] = { tag = "expression",  bp.expression }
    end

    -- internal use only
    response.attr.expression = nil
    response.attr.condition = nil
    response.attr.temporary = nil -- TODO: the specification is not clear whether this should be provided, see other implementations
    return response
  end

  --- Register an event to be triggered.
  -- @param event event name to register (must be "over", "out" or "into")
  function core.events.register(event)
    local thread = active_session.coro[1]
    log("DEBUG", "Registered %s event for %s (%d)", event, tostring(thread), stack_levels[thread])
    if event == "into" then
      step_into = true
    else
      waiting_sessions[thread] = { event, stack_levels[thread] }
    end
  end

  --- Returns if an event (step into, over, out) is triggered.
  -- Does *not* discard events (even if they match) as event must be discarded manually if a breakpoint match before anyway.
  -- @return true if an event has matched, false otherwise
  function core.events.does_match()
    if step_into then return true end

    local thread = active_session.coro[1]
    local event = waiting_sessions[thread]
    if event then
      local event_type, target_level = unpack(event)
      local current_level = stack_levels[thread]

      if (event_type == "over" and current_level <= target_level) or   -- step over
        (event_type == "out"  and current_level <  target_level) then -- step out
        log("DEBUG", "Event %s matched!", event_type)
        return true
      end
    end
    return false
  end

  --- Discards event for current thread (if any)
  function core.events.discard()
    waiting_sessions[active_session.coro[1]] = nil
    step_into = nil
  end
end

-------------------------------------------------------------------------------
--  Debugger main loop
-------------------------------------------------------------------------------

--- Send the XML response to the previous continuation command and clear the previous context
function core.previous_context_response(self, reason)
  self.previous_context.status = self.state
  self.previous_context.reason = reason or "ok"
  dbgp.send_xml(self.skt, { tag = "response", attr = self.previous_context } )
  self.previous_context = nil
end

local function cleanup()
  coroutine.resume, coroutine.wrap = coresume, cowrap
  for _, coro in pairs(core.active_coroutines.from_id) do
    debug.sethook(coro)
  end
  -- to remove hook on the main coroutine, it must be the current one (otherwise, this is a no-op) and this function
  -- have to be called adain later on the main thread to finish cleaup
  debug.sethook()
  core.active_coroutines.from_id, core.active_coroutines.from_coro = { }, { }
end

--- This function handles the debugger commands while the execution is paused. This does not use coroutines because there is no
-- way to get main coro in Lua 5.1 (only in 5.2)
local function debugger_loop(self, async_packet)
  self.skt:settimeout(nil) -- set socket blocking

  -- in async mode, the debugger does not wait for another command before continuing and does not modify previous_context
  local async_mode = async_packet ~= nil

  if self.previous_context and not async_mode then
    self.state = "break"
    core.previous_context_response(self)
  end
  self.stack = context.ContextManager(self.coro) -- will be used to mutualize context allocation for each loop

  while true do
    -- reads packet
    local packet = async_packet or dbgp.read_packet(self.skt)
    if not packet then
      log("WARNING", "lost debugger connection")
      cleanup()
      break
    end

    async_packet = nil
    log("DEBUG", packet)
    local cmd, args, data = dbgp.cmd_parse(packet)

    -- FIXME: command such as continuations sent in async mode could lead both engine and IDE in inconsistent state :
    --        make a blacklist/whitelist of forbidden or allowed commands in async ?
    -- invoke function
    local func = commands[cmd]
    if func then
      local ok, cont = xpcall(function() return func(self, args, data) end, debug.traceback)
      if not ok then -- internal exception
        local code, msg, attr
        if type(cont) == "table" and getmetatable(cont) == dbgp.DBGP_ERR_METATABLE then
          code, msg, attr = cont.code, cont.message, cont.attr
        else
          code, msg, attr = 998, tostring(cont), { }
        end
        log("ERROR", "Command %s caused: (%d) %s", cmd, code, tostring(msg))
        attr.command, attr.transaction_id = cmd, args.i
        dbgp.send_xml(self.skt, { tag = "response", attr = attr, dbgp.make_error(code, msg) } )
      elseif cont then
        self.previous_context = { command = cmd, transaction_id = args.i }
        break
      elseif cont == nil and async_mode then
        break
      elseif cont == false then -- In case of commands that fully resumes debugger loop, the mode is sync
        async_mode = false
      end
    else
      log("Got unknown command: "..cmd)
      dbgp.send_xml(self.skt, { tag = "response", attr = { command = cmd, transaction_id = args.i, }, dbgp.make_error(4) } )
    end
  end

  self.stack = nil -- free allocated contexts
  self.state = "running"
  self.skt:settimeout(0) -- reset socket to async
end

-- Stack handling can be pretty complex sometimes, especially with LuaJIT (as tail-call optimization are
-- more aggressive as stock Lua). So all debugger stuff is done in another coroutine, which leave the program
-- stack in a clean state and allow faster and clearer stack operations (no need to remove all debugger calls
-- from stack for each operation).
-- However, this does not always work with stock Lua 5.1 as the main coroutine cannot be referenced
-- (coroutine.running() return nil). For this particular case, the debugger loop is started on the top of
-- program stack and every stack operation is relative the the hook level (see MainThread in util.lua).
local function line_hook(line)
  local do_break, packet = nil, nil
  local info = active_session.coro:getinfo(0, "S")
  local uri = platform.get_uri(info.source)
  if uri and uri ~= debugger_uri and uri ~= transportmodule_uri then -- the debugger does not break if the source is not known
    do_break = core.breakpoints.at(uri, line) or core.events.does_match()
    if do_break then
      core.events.discard()
    end

    -- check for async commands
    if not do_break then
      packet = dbgp.read_packet(active_session.skt)
      if packet then do_break = true end
    end
  end

  if do_break then
    local success, err = pcall(debugger_loop, active_session, packet)
    if not success then log("ERROR", "Error while debug loop: "..err) end
  end
end

local line_hook_coro = cocreate(function(line)
  while true do
    line_hook(line)
    line = coyield()
  end
end)

local function debugger_hook(event, line)
  local thread = corunning() or "main"
  if event == "call" then
    stack_levels[thread] = stack_levels[thread] + 1
  elseif event == "tail call" then
  -- tail calls has no effects on stack handling: it is only used only for step commands but a such even does not
  -- interfere with any of them
  elseif event == "return" or event == "tail return" then
    stack_levels[thread] = stack_levels[thread] - 1
  else -- line event: check for breakpoint
    active_session.coro = util.CurrentThread(corunning())
    if active_session.coro[1] == "main" then
      line_hook(line)
    else
      -- run the debugger loop in another thread on the other cases (simplifies stack handling)
      assert(coresume(line_hook_coro, line))
    end
    active_session.coro = nil
  end
end

if rawget(_G, "jit") then
  debugger_hook = function(event, line)
    local thread = corunning() or "main"
    if event == "call" then
      if debug.getinfo(2, "S").what == "C" then return end
      stack_levels[thread] = stack_levels[thread] + 1
    elseif event == "return" or event == "tail return" then
      -- Return hooks are not called for tail calls in JIT (but unlike 5.2 there is no way to know whether a call is tail or not).
      -- So the only reliable way to know stack depth is to walk it.
      local depth = 2
      -- TODO: find the fastest way to call getinfo ('what' parameter)
      while debug.getinfo(depth, "f") do depth = depth + 1 end
      stack_levels[thread] = depth - 2
    elseif event == "line" then
      active_session.coro = util.CurrentThread(corunning())
      if active_session.coro[1] == "main" then
        line_hook(line)
      else
        -- run the debugger loop in another thread on the other cases (simplifies stack handling)
        assert(coresume(line_hook_coro, line))
      end
      active_session.coro = nil
    end
  end
end

local function sendInitPacket(skt,idekey)
  -- get the root script path (the highest possible stack index)
  local source
  for i=2, math.huge do
    local info = debug.getinfo(i)
    if not info then break end
    source = platform.get_uri(info.source) or source
  end
  if not source then source = "unknown:/" end -- when loaded before actual script (with a command line switch)

  -- generate some kind of thread identifier
  local thread = corunning() or "main"
  stack_levels[thread] = 1 -- the return event will set the counter to 0
  local sessionid = tostring(os.time()) .. "_" .. tostring(thread)

  dbgp.send_xml(skt, { tag = "init", attr = {
    appid = "Lua DBGp",
    idekey = idekey,
    session = sessionid,
    thread = tostring(thread),
    parent = "",
    language = "Lua",
    protocol_version = "1.0",
    fileuri = source
  } })
  
  return sessionid
end

local function init(host, port, idekey, transport, executionplatform, workingdirectory, nbRetry)
  -- get connection data
  local host = host or os.getenv "DBGP_IDEHOST" or "127.0.0.1"
  local port = port or os.getenv "DBGP_IDEPORT" or "10000"
  local idekey = idekey or os.getenv("DBGP_IDEKEY") or "luaidekey"

  -- init plaform module
  local executionplatform = executionplatform or os.getenv("DBGP_PLATFORM") or nil
  local workingdirectory = workingdirectory or os.getenv("DBGP_WORKINGDIR") or nil
  platform.init(executionplatform,workingdirectory)

  -- get transport layer
  local transportpath = transport or os.getenv("DBGP_TRANSPORT") or "debugger.transport.luasocket"
  local transport = require(transportpath)

  -- nb retry for connection
  local nbRetry = nbRetry or os.getenv("DBGP_NBRETRY") or 10
  nbRetry = math.max(nbRetry,1)

  -- install base64 functions into util
  util.b64, util.rawb64, util.unb64 = transport.b64, transport.rawb64, transport.unb64

  -- get the debugger and transport layer URI
  debugger_uri = platform.get_uri(debug.getinfo(1).source)
  transportmodule_uri = platform.get_uri(debug.getinfo(transport.create).source)

  -- try to connect several times: if IDE launches both process and server at same time, first connect attempts may fail
  local skt,ok, err
  print(string.format("Debugger v%s", DBGP_CLIENT_VERSION))
  print(string.format("Debugger: Trying to connect to %s:%s ... ", host, port))

  local timeelapsed = 0
  local sessionid = nil
  for i=1,nbRetry do
    -- try to connect to DBGP server
    skt = assert(transport.create())
    skt:settimeout(nil)
    ok, err = skt:connect(host, port)
    if ok then
      sessionid = sendInitPacket(skt,idekey)
      -- test if socket is closed
      ok, err = skt:receive(0)
      if err == nil then print("Debugger: Connection succeed.") break end
    end

    if err ~= nil then
      -- failed to connect
      print(string.format("Debugger: Failed to connect to %s:%s (%s)", host, port, err))
      skt:close()

      -- wait&retry
      local timetowait = math.min(3, math.max(timeelapsed/2, 0.25))
      if i < nbRetry then 
        print(string.format("Debugger: Retrying to connect to %s:%s in %.2fs ... ", host, port,timetowait))
        transport.sleep(timetowait)
        timeelapsed  = timeelapsed+timetowait
      end
    end
  end
  if err then error(string.format("Cannot connect to %s:%d : %s", host, port, err)) end  

  --FIXME util.CurrentThread(corunning) => util.CurrentThread(corunning()) WHAT DOES IT FIXES ??
  local sess = { skt = skt, state = "starting", id = sessionid, coro = util.CurrentThread(corunning) }
  active_session = sess
  debugger_loop(sess)

  -- set debug hooks
  debug.sethook(debugger_hook, "rlc")

  -- install coroutine collecting functions.
  -- TODO: maintain a list of *all* coroutines can be overkill (for example, the ones created by copcall), make a extension point to
  -- customize debugged coroutines
  -- coroutines are referenced during their first resume (so we are sure that they always have a stack frame)
  local function resume_handler(coro, ...)
    if costatus(coro) == "dead" then
      local coro_id = core.active_coroutines.from_coro[coro]
      core.active_coroutines.from_id[coro_id] = nil
      core.active_coroutines.from_coro[coro] = nil
      stack_levels[coro] = nil
    end
    return ...
  end

  function coroutine.resume(coro, ...)
    if not stack_levels[coro] then
      -- first time referenced
      stack_levels[coro] = 0
      core.active_coroutines.n = core.active_coroutines.n + 1
      core.active_coroutines.from_id[core.active_coroutines.n] = coro
      core.active_coroutines.from_coro[coro] = core.active_coroutines.n
      debug.sethook(coro, debugger_hook, "rlc")
    end
    return resume_handler(coro, coresume(coro, ...))
  end

  -- coroutine.wrap uses directly C API for coroutines and does not trigger our overridden coroutine.resume
  -- so this is an implementation of wrap in pure Lua
  local function wrap_handler(status, ...)
    if not status then error((...)) end
    return ...
  end

  function coroutine.wrap(f)
    local coro = coroutine.create(f)
    return function(...)
      return wrap_handler(coroutine.resume(coro, ...))
    end
  end

  return sess
end

return init