// Here is the core api for the hilbi shell itself
// Basically, stuff about the shell itself and other functions
// go here.
package main

import (
	"fmt"
	"os"
	"os/exec"
	"runtime"
	"strings"
	"syscall"
	"time"

	"hilbish/util"

	"github.com/yuin/gopher-lua"
	"mvdan.cc/sh/v3/interp"
)

var exports = map[string]lua.LGFunction {
	"alias": hlalias,
	"appendPath": hlappendPath,
	"cwd": hlcwd,
	"exec": hlexec,
	"multiprompt": hlmlprompt,
	"prependPath": hlprependPath,
	"prompt": hlprompt,
	"interval": hlinterval,
	"read": hlread,
	"run": hlrun,
	"timeout": hltimeout,
	"which": hlwhich,
}

var greeting string

func hilbishLoader(L *lua.LState) int {
	mod := L.SetFuncs(L.NewTable(), exports)

	host, _ := os.Hostname()
	username := curuser.Username

	greeting = `Welcome to {magenta}Hilbish{reset}, {cyan}` + curuser.Username + `{reset}.
The nice lil shell for {blue}Lua{reset} fanatics!
`

	if runtime.GOOS == "windows" {
		username = strings.Split(username, "\\")[1] // for some reason Username includes the hostname on windows
	}

	util.SetField(L, mod, "ver", lua.LString(version), "Hilbish version")
	util.SetField(L, mod, "user", lua.LString(username), "Username of user")
	util.SetField(L, mod, "host", lua.LString(host), "Host name of the machine")
	util.SetField(L, mod, "home", lua.LString(curuser.HomeDir), "Home directory of the user")
	util.SetField(L, mod, "dataDir", lua.LString(dataDir), "Directory for Hilbish's data files")
	util.SetField(L, mod, "interactive", lua.LBool(interactive), "If this is an interactive shell")
	util.SetField(L, mod, "login", lua.LBool(interactive), "Whether this is a login shell")
	util.SetField(L, mod, "greeting", lua.LString(greeting), "Hilbish's welcome message for interactive shells. It has Lunacolors formatting.")
	util.Document(L, mod, "Hilbish's core API, containing submodules and functions which relate to the shell itself.")

	// hilbish.userDir table
	hshuser := L.NewTable()

	util.SetField(L, hshuser, "config", lua.LString(confDir), "User's config directory")
	util.SetField(L, hshuser, "data", lua.LString(userDataDir), "XDG data directory")
	util.Document(L, hshuser, "User directories to store configs and/or modules.")
	L.SetField(mod, "userDir", hshuser)

	// hilbish.aliases table
	aliases = NewAliases()
	aliasesModule := aliases.Loader(L)
	util.Document(L, aliasesModule, "Alias inferface for Hilbish.")
	L.SetField(mod, "aliases", aliasesModule)

	// hilbish.history table
	historyModule := lr.Loader(L)
	util.Document(L, historyModule, "History interface for Hilbish.")
	L.SetField(mod, "history", historyModule)

	L.Push(mod)

	return 1
}

// run(cmd)
// Runs `cmd` in Hilbish's sh interpreter.
// --- @param cmd string
func hlrun(L *lua.LState) int {
	var exitcode uint8
	cmd := L.CheckString(1)
	err := execCommand(cmd, cmd)

	if code, ok := interp.IsExitStatus(err); ok {
		exitcode = code
	} else if err != nil {
		exitcode = 1
	}

	L.Push(lua.LNumber(exitcode))
	return 1
}

// cwd()
// Returns the current directory of the shell
func hlcwd(L *lua.LState) int {
	cwd, _ := os.Getwd()

	L.Push(lua.LString(cwd))

	return 1
}

func getenv(key, fallback string) string {
    value := os.Getenv(key)
    if len(value) == 0 {
        return fallback
    }
    return value
}

// read(prompt) -> input?
// Read input from the user, using Hilbish's line editor/input reader.
// This is a separate instance from the one Hilbish actually uses.
// Returns `input`, will be nil if ctrl + d is pressed, or an error occurs (which shouldn't happen)
// --- @param prompt string
func hlread(L *lua.LState) int {
	luaprompt := L.CheckString(1)
	lualr := newLineReader(luaprompt)

	input, err := lualr.Read()
	if err != nil {
		L.Push(lua.LNil)
		return 1
	}

	L.Push(lua.LString(input))
	return 1
}

/*
prompt(str)
Changes the shell prompt to `str`
There are a few verbs that can be used in the prompt text.
These will be formatted and replaced with the appropriate values.
`%d` - Current working directory
`%u` - Name of current user
`%h` - Hostname of device
--- @param str string
*/
func hlprompt(L *lua.LState) int {
	prompt = L.CheckString(1)

	return 0
}

// multiprompt(str)
// Changes the continued line prompt to `str`
// --- @param str string
func hlmlprompt(L *lua.LState) int {
	multilinePrompt = L.CheckString(1)

	return 0
}

// alias(cmd, orig)
// Sets an alias of `orig` to `cmd`
// --- @param cmd string
// --- @param orig string
func hlalias(L *lua.LState) int {
	alias := L.CheckString(1)
	source := L.CheckString(2)

	aliases.Add(alias, source)

	return 1
}

// appendPath(dir)
// Appends `dir` to $PATH
// --- @param dir string|table
func hlappendPath(L *lua.LState) int {
	// check if dir is a table or a string
	arg := L.Get(1)
	fmt.Println(arg.Type())
	if arg.Type() == lua.LTTable {
		arg.(*lua.LTable).ForEach(func(k lua.LValue, v lua.LValue) {
			appendPath(v.String())
		})
	} else if arg.Type() == lua.LTString {
		appendPath(arg.String())
	} else {
		L.RaiseError("bad argument to appendPath (expected string or table, got %v)", L.Get(1).Type().String())
	}

	return 0
}

func appendPath(dir string) {
	dir = strings.Replace(dir, "~", curuser.HomeDir, 1)
	pathenv := os.Getenv("PATH")

	// if dir isnt already in $PATH, add it
	if !strings.Contains(pathenv, dir) {
		os.Setenv("PATH", pathenv + string(os.PathListSeparator) + dir)
	}
}

// exec(cmd)
// Replaces running hilbish with `cmd`
// --- @param cmd string
func hlexec(L *lua.LState) int {
	cmd := L.CheckString(1)
	cmdArgs, _ := splitInput(cmd)
	cmdPath, err := exec.LookPath(cmdArgs[0])
	if err != nil {
		fmt.Println(err)
		// if we get here, cmdPath will be nothing
		// therefore nothing will run
	}

	// syscall.Exec requires an absolute path to a binary
	// path, args, string slice of environments
	// TODO: alternative for windows
	syscall.Exec(cmdPath, cmdArgs, os.Environ())
	return 0 // random thought: does this ever return?
}

// goro(fn)
// Puts `fn` in a goroutine
// --- @param fn function
func hlgoroutine(L *lua.LState) int {
	fn := L.CheckFunction(1)
	argnum := L.GetTop()
	args := make([]lua.LValue, argnum)
	for i := 1; i <= argnum; i++ {
		args[i - 1] = L.Get(i)
	}

	// call fn
	go func() {
		L.CallByParam(lua.P{
			Fn:      fn,
			NRet:    0,
			Protect: true,
		}, args...)
	}()

	return 0
}

// timeout(cb, time)
// Runs the `cb` function after `time` in milliseconds
// --- @param cb function
// --- @param time number
func hltimeout(L *lua.LState) int {
	cb := L.CheckFunction(1)
	ms := L.CheckInt(2)

	timeout := time.Duration(ms) * time.Millisecond
	time.Sleep(timeout)

	L.CallByParam(lua.P{
		Fn:      cb,
		NRet:    0,
		Protect: true,
	})
	return 0
}

// interval(cb, time)
// Runs the `cb` function every `time` milliseconds
// --- @param cb function
// --- @param time number
func hlinterval(L *lua.LState) int {
	intervalfunc := L.CheckFunction(1)
	ms := L.CheckInt(2)
	interval := time.Duration(ms) * time.Millisecond

	ticker := time.NewTicker(interval)
	stop := make(chan lua.LValue)

	go func() {
		for {
			select {
			case <-ticker.C:
				if err := L.CallByParam(lua.P{
					Fn: intervalfunc,
					NRet: 0,
					Protect: true,
				}); err != nil {
					fmt.Fprintln(os.Stderr, "Error in interval function:\n\n", err)
					stop <- lua.LTrue // stop the interval
				}
			case <-stop:
				ticker.Stop()
				return
			}
		}
	}()

	L.Push(lua.LChannel(stop))
	return 1
}

// complete(scope, cb)
// Registers a completion handler for `scope`.
// A `scope` is currently only expected to be `command.<cmd>`,
// replacing <cmd> with the name of the command (for example `command.git`).
// `cb` must be a function that returns a table of the entries to complete.
// Nested tables will be used as sub-completions.
func hlcomplete(L *lua.LState) int {
	scope := L.CheckString(1)
	cb := L.CheckFunction(2)

	luaCompletions[scope] = cb

	return 0
}

// prependPath(dir)
// Prepends `dir` to $PATH
func hlprependPath(L *lua.LState) int {
	dir := L.CheckString(1)
	dir = strings.Replace(dir, "~", curuser.HomeDir, 1)
	pathenv := os.Getenv("PATH")

	// if dir isnt already in $PATH, add in
	if !strings.Contains(pathenv, dir) {
		os.Setenv("PATH", dir + string(os.PathListSeparator) + pathenv)
	}

	return 0
}

// which(binName)
// Searches for an executable called `binName` in the directories of $PATH
func hlwhich(L *lua.LState) int {
	binName := L.CheckString(1)
	path, err := exec.LookPath(binName)
	if err != nil {
		l.Push(lua.LNil)
		return 1
	}
	
	l.Push(lua.LString(path))
	return 1
}