-- @module hilbish.runner
local snail = require 'snail'
local currentRunner = 'hybrid'
local runners = {}

-- lsp shut up
hilbish = hilbish

--- Get a runner by name.
--- @param name string Name of the runner to retrieve.
--- @return table
function hilbish.runner.get(name)
	local r = runners[name]

	if not r then
		error(string.format('runner %s does not exist', name))
	end

	return r
end

--- Adds a runner to the table of available runners.
--- If runner is a table, it must have the run function in it.
--- @param name string Name of the runner
--- @param runner function|table 
function hilbish.runner.add(name, runner)
	if type(name) ~= 'string' then
		error 'expected runner name to be a table'
	end

	if type(runner) == 'function' then
		runner = {run = runner} -- this probably looks confusing
	end

	if type(runner) ~= 'table' then
		error 'expected runner to be a table or function'
	end

	if runners[name] then
		error(string.format('runner %s already exists', name))
	end

	hilbish.runner.set(name, runner)
end

--- *Sets* a runner by name. The difference between this function and
--- add, is set will *not* check if the named runner exists.
--- The runner table must have the run function in it.
--- @param name string
--- @param runner table
function hilbish.runner.set(name, runner)
	if not runner.run or type(runner.run) ~= 'function' then
		error 'run function in runner missing'
	end

	runners[name] = runner
end

--- Executes `cmd` with a runner.
--- If `runnerName` is not specified, it uses the default Hilbish runner.
--- @param cmd string
--- @param runnerName string?
--- @return table
function hilbish.runner.exec(cmd, runnerName)
	if not runnerName then runnerName = currentRunner end

	local r = hilbish.runner.get(runnerName)

	return r.run(cmd)
end

--- Sets Hilbish's runner mode by name.
--- @param name string
function hilbish.runner.setCurrent(name)
	hilbish.runner.get(name) -- throws if it doesnt exist.
	currentRunner = name
end

--- Returns the current runner by name.
--- @returns string
function hilbish.runner.getCurrent()
	return currentRunner
end

local function finishExec(exitCode, input, priv)
	hilbish.exitCode = exitCode
	bait.throw('command.exit', exitCode, input, priv)
end

local function continuePrompt(prev, newline)
	local multilinePrompt = hilbish.multiprompt()
	-- the return of hilbish.read is nil when error or ctrl-d
	local cont = hilbish.read(multilinePrompt)
	if not cont then
		return
	end

	if newline then
		cont = '\n' .. cont
	end

	if cont:match '\\$' then
		cont = cont:gsub('\\$', '') .. '\n'
	end

	return prev .. cont
end

--- Runs `input` with the currently set Hilbish runner.
--- This method is how Hilbish executes commands.
--- `priv` is an optional boolean used to state if the input should be saved to history.
-- @param input string
-- @param priv bool
function hilbish.runner.run(input, priv)
	local command = hilbish.aliases.resolve(input)
	bait.throw('command.preexec', input, command)

	::rerun::
	local runner = hilbish.runner.get(currentRunner)
	local ok, out = pcall(runner.run, input)
	if not ok then
		io.stderr:write(out .. '\n')
		finishExec(124, out.input, priv)
		return
	end

	if out.continue then
		local contInput = continuePrompt(input, out.newline)
		if contInput then
			input = contInput
			goto rerun
		end
	end

	if out.err then
		local fields = string.split(out.err, ': ')
		if fields[2] == 'not-found' or fields[2] == 'not-executable' then
			bait.throw('command.' .. fields[2], fields[1])
		else
			io.stderr:write(out.err .. '\n')
		end
	end
	finishExec(out.exitCode, out.input, priv)
end

function hilbish.runner.sh(input)
	return hilbish.snail:run(input)
end

hilbish.runner.add('hybrid', function(input)
	local cmdStr = hilbish.aliases.resolve(input)

	local res = hilbish.runner.lua(cmdStr)
	if not res.err then
		return res
	end

	return hilbish.runner.sh(input)
end)

hilbish.runner.add('hybridRev', function(input)
	local res = hilbish.runner.sh(input)
	if not res.err then
		return res
	end

	local cmdStr = hilbish.aliases.resolve(input)
	return hilbish.runner.lua(cmdStr)
end)

hilbish.runner.add('lua', function(input)
	local cmdStr = hilbish.aliases.resolve(input)
	return hilbish.runner.lua(cmdStr)
end)

hilbish.runner.add('sh', hilbish.runner.sh)
hilbish.runner.setCurrent 'hybrid'