local destination_engine = require("clever_tee.destination_engine")
local domain = require("clever_tee.domain")
local sequence_state = require("clever_tee.sequence_state")
local state_transitions = require("clever_tee.state_transitions")
local text_topology = require("clever_tee.text_topology")

local M = {}
local MotionExecutor = {}
M.MotionExecutor = MotionExecutor

M.ExecutionPath = {
  VISUAL = "visual",
  COMMAND = "command",
}

local executor_records = setmetatable({}, { __mode = "k" })

local function fail(message, level)
  error(message, (level or 1) + 1)
end

function M.execution_path(context)
  context = domain.ModeContext.from_full_mode(context)
  if context.visual_kind ~= nil then
    return M.ExecutionPath.VISUAL
  end
  return M.ExecutionPath.COMMAND
end

function M.moved_forward(origin, destination)
  origin = domain.Position.coerce(origin)
  destination = domain.Position.coerce(destination)
  return domain.Position.compare(destination, origin) > 0
end

function M.command_moved_forward(descriptor, origin, destination)
  descriptor = domain.Descriptor.from_string(descriptor)
  origin = domain.Position.coerce(origin)
  destination = domain.Position.coerce(destination)
  if descriptor.family == domain.Family.TILL
    and domain.Position.stationary(origin, destination)
  then
    return false
  end
  return M.moved_forward(origin, destination)
end

function M.create_dot_payload(plan)
  if not domain.ResolvedMotionPlan.is(plan) then
    fail("dot payload plan must be a ResolvedMotionPlan", 2)
  end
  return domain.DotPayload.new(plan.descriptor, plan.target_plan.target)
end

function M.plan_for_dot_payload(plan, payload)
  if not domain.ResolvedMotionPlan.is(plan) then
    fail("dot replay plan must be a ResolvedMotionPlan", 2)
  end
  if not domain.DotPayload.is(payload) then
    fail("dot replay payload must be a DotPayload", 2)
  end
  if payload.target ~= plan.target_plan.target then
    fail("dot replay payload target must match its resolved target plan", 2)
  end
  return domain.ResolvedMotionPlan.new({
    target_plan = plan.target_plan,
    descriptor = payload.descriptor,
    search_scope = plan.search_scope,
    endpoint_policy = plan.endpoint_policy,
  })
end

local function copy_options(options)
  local result = {}
  for key, value in pairs(options or {}) do
    result[key] = value
  end
  return result
end

local function normalize_options(options, dependencies)
  if MotionExecutor.is(options) and dependencies == nil then
    return options
  end
  if type(options) ~= "table" then
    fail("MotionExecutor options must be a table", 3)
  end
  if options.host ~= nil then
    if dependencies ~= nil then
      fail("MotionExecutor dependencies must be part of its options", 3)
    end
    return options
  end
  local result = copy_options(dependencies)
  result.host = options
  return result
end

local function require_host(host)
  if type(host) ~= "table"
    or type(host.read_cursor) ~= "function"
    or type(host.read_encoding) ~= "function"
    or type(host.read_pending_operator) ~= "function"
    or type(host.read_selection) ~= "function"
    or type(host.read_text) ~= "function"
    or type(host.apply_cursor) ~= "function"
    or type(host.apply_selection) ~= "function"
    or type(host.set_operator_inclusive) ~= "function"
    or type(host.register_dot_repeat) ~= "function"
  then
    fail("MotionExecutor host must provide movement state", 3)
  end
  return host
end

local function require_destination_engine(engine)
  engine = engine or destination_engine.new()
  if type(engine) ~= "table" or type(engine.calculate) ~= "function" then
    fail("MotionExecutor destination engine must provide calculate", 3)
  end
  return engine
end

local function require_feedback_service(service)
  if service ~= nil and (type(service) ~= "table"
      or type(service.migrate_command) ~= "function")
  then
    fail("MotionExecutor feedback service must provide migrate_command", 3)
  end
  return service
end

local function require_state(state)
  state = state or sequence_state.get()
  if not sequence_state.is(state) then
    fail("MotionExecutor state must be the plugin-global SequenceState", 3)
  end
  return state
end

local function require_transitions(transitions, state)
  transitions = transitions or state_transitions.new(state)
  if type(transitions) ~= "table"
    or type(transitions.CommitCommandSuccess) ~= "function"
    or type(transitions.CommitVisualSuccess) ~= "function"
  then
    fail("MotionExecutor transitions must commit motion success", 3)
  end
  return transitions
end

local executor_metatable = {
  __index = MotionExecutor,
  __newindex = function()
    fail("MotionExecutor values are immutable", 2)
  end,
  __tostring = function()
    return "motion-executor"
  end,
  __metatable = "clever_tee.motion_executor.MotionExecutor",
}

function MotionExecutor.new(options, dependencies)
  options = normalize_options(options, dependencies)
  if MotionExecutor.is(options) then
    return options
  end

  local executor = setmetatable({}, executor_metatable)
  local state = require_state(options.state)
  executor_records[executor] = {
    host = require_host(options.host),
    destination_engine = require_destination_engine(
      options.destination_engine or options.engine
    ),
    feedback_service = require_feedback_service(
      options.feedback_service or options.feedback
    ),
    state = state,
    transitions = require_transitions(
      options.transitions or options.state_transitions,
      state
    ),
  }
  return executor
end

function MotionExecutor.is(value)
  return type(value) == "table" and executor_records[value] ~= nil
end

local function execution_request(
  view,
  context,
  plan,
  count,
  first_move,
  execution_options
)
  if not text_topology.TextView.is(view) then
    fail("motion execution view must be a TextView", 3)
  end
  context = domain.ModeContext.from_full_mode(context)
  if not domain.ResolvedMotionPlan.is(plan) then
    fail("motion execution plan must be a ResolvedMotionPlan", 3)
  end
  count = domain.Count.new(count)
  if type(first_move) ~= "boolean" then
    fail("motion execution first_move must be a Boolean", 3)
  end
  execution_options = execution_options or {}
  if type(execution_options) ~= "table" then
    fail("motion execution options must be a table", 3)
  end
  local dot_payload = execution_options.dot_payload
  if dot_payload ~= nil and not domain.DotPayload.is(dot_payload) then
    fail("motion execution dot_payload must be a DotPayload", 3)
  end
  local register_dot_repeat = execution_options.register_dot_repeat
  if register_dot_repeat == nil then
    register_dot_repeat = true
  elseif type(register_dot_repeat) ~= "boolean" then
    fail("motion execution register_dot_repeat must be a Boolean", 3)
  end
  return {
    view = view,
    context = context,
    plan = plan,
    count = count,
    first_move = first_move,
    dot_payload = dot_payload,
    register_dot_repeat = register_dot_repeat,
  }
end

local function calculate(executor, request, origin)
  return executor_records[executor].destination_engine:calculate(
    request.view,
    origin,
    request.plan,
    request.count,
    request.first_move
  )
end

local function command_action(
  host,
  outcome,
  descriptor,
  dot_payload,
  use_current_position
)
  return domain.ActionOutcome.new({
    kind = outcome.complete
        and domain.ActionKind.MOVEMENT
      or domain.ActionKind.FAILED_SEARCH,
    position = use_current_position and host:read_cursor() or outcome.endpoint,
    search_outcome = outcome,
    effective_descriptor = descriptor,
    dot_payload = dot_payload,
  })
end

local function register_dot_replay(executor, request, payload)
  local host = executor_records[executor].host
  host:register_dot_repeat(payload, function(replayed_payload, replay_count)
    return executor:execute_dot(
      text_topology.from_host(host),
      request.context,
      request.plan,
      replayed_payload,
      replay_count
    )
  end)
end

local function migrate_command_feedback(executor, request, origin, outcome)
  local record = executor_records[executor]
  local feedback = record.feedback_service
  if feedback == nil then
    return
  end
  feedback:migrate_command({
    context = request.context,
    origin = origin,
    destination = outcome.endpoint,
    plan = request.plan,
    resolved_motion_plan = request.plan,
    outcome = outcome,
    count = request.count,
    first_move = request.first_move,
    moved_forward = request.moved_forward,
    previous_moved_forward = record.state.moved_forward,
    previous_moved_forward_initialized = record.state.moved_forward_initialized,
  })
end

function MotionExecutor:_execute_command(request)
  local host = executor_records[self].host
  local origin = host:read_cursor()
  local pending_operator = request.context.operator
      and host:read_pending_operator()
    or nil
  local outcome = calculate(self, request, origin)
  if outcome.successful_steps > 0 then
    if request.context.operator
      and request.plan.descriptor.direction == domain.Direction.FORWARD
    then
      host:set_operator_inclusive(true)
    end
    host:apply_cursor(outcome.endpoint, {
      context = request.context,
      descriptor = request.plan.descriptor,
      origin = origin,
    })
  end
  if not outcome.complete then
    return command_action(
      host,
      outcome,
      request.plan.descriptor,
      nil,
      pending_operator ~= nil and pending_operator ~= ""
    )
  end
  request.moved_forward = M.command_moved_forward(
    request.plan.descriptor,
    origin,
    outcome.endpoint
  )
  migrate_command_feedback(self, request, origin, outcome)
  executor_records[self].transitions:CommitCommandSuccess(
    request.context,
    outcome.endpoint,
    request.moved_forward
  )
  local dot_payload
  if pending_operator ~= nil and pending_operator ~= "" then
    dot_payload = request.dot_payload or M.create_dot_payload(request.plan)
    if request.register_dot_repeat then
      register_dot_replay(self, request, dot_payload)
    end
  end
  return command_action(
    host,
    outcome,
    request.plan.descriptor,
    dot_payload,
    pending_operator ~= nil and pending_operator ~= ""
  )
end

function MotionExecutor:_execute_visual(request)
  local host = executor_records[self].host
  local selection = host:read_selection()
  if not domain.Selection.is(selection)
    or not selection.active
    or selection.kind ~= request.context.visual_kind
  then
    fail("Visual motion execution requires its active selection kind", 2)
  end
  local origin = host:read_cursor()
  local outcome = calculate(self, request, origin)
  request.selection = selection
  if outcome.successful_steps > 0 then
    host:apply_selection(selection:with_focus(outcome.endpoint))
  end
  if not outcome.complete then
    return domain.ActionOutcome.from_search(outcome, request.plan.descriptor)
  end
  executor_records[self].transitions:CommitVisualSuccess(
    request.context,
    outcome.endpoint
  )
  return domain.ActionOutcome.from_search(outcome, request.plan.descriptor)
end

function MotionExecutor:execute(
  view,
  context,
  plan,
  count,
  first_move,
  execution_options
)
  local request = execution_request(
    view,
    context,
    plan,
    count,
    first_move,
    execution_options
  )
  if M.execution_path(request.context) == M.ExecutionPath.VISUAL then
    return self:_execute_visual(request)
  end
  return self:_execute_command(request)
end

function MotionExecutor:execute_dot(view, context, plan, payload, count)
  return self:execute(
    view,
    context,
    M.plan_for_dot_payload(plan, payload),
    count,
    false,
    {
      dot_payload = payload,
      register_dot_repeat = false,
    }
  )
end

function M.new(options, dependencies)
  return MotionExecutor.new(options, dependencies)
end

function M.execute(host, view, context, plan, count, first_move, dependencies)
  return MotionExecutor.new(host, dependencies):execute(
    view,
    context,
    plan,
    count,
    first_move
  )
end

M.run = M.execute

setmetatable(M, {
  __call = function(_, options, dependencies)
    return MotionExecutor.new(options, dependencies)
  end,
})

return M