package main

import (
	"errors"
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/peterh/liner"
)

type libraryFiles []string

func (l *libraryFiles) String() string {
	return strings.Join(*l, ", ")
}

func (l *libraryFiles) Set(value string) error {
	*l = append(*l, strings.TrimSpace(value))
	return nil
}

func historyFn() string {
	dataHome := os.Getenv("XDG_DATA_HOME")
	home := os.Getenv("HOME")
	if dataHome == "" {
		dataHome = filepath.Join(home, ".local/share/")
	}
	prosperDir := filepath.Join(dataHome, "prosper")
	os.MkdirAll(prosperDir, 0755)
	return filepath.Join(prosperDir, ".history")
}

func completer(d Dictionary) liner.Completer {
	return func(line string) []string {
		candidates := []string{}
		words := strings.Split(line, " ")
		for w := range d {
			if strings.HasPrefix(w, words[len(words)-1]) {
				// must reconstruct the _full_ line to return for the completer
				pref := strings.Join(words[:len(words)-1], " ")
				if len(pref) != 0 {
					candidates = append(candidates, pref+" "+w)
				} else {
					candidates = append(candidates, w)
				}
			}
		}
		return candidates
	}
}

func main() {
	// flag setup
	var libs libraryFiles
	flag.Var(&libs, "l", "propser library file (may be repeated)")
	debug := flag.Bool("debug", false, "output debugging information")
	flag.Parse()

	// create main context
	stack := Stack{values: []int{}}
	rstack := Stack{values: []int{}}
	ifstack := Stack{values: []int{}}

	dict := Dictionary{}

	c := Context{
		Dictionary: dict,
		Stack:      &stack,
		RStack:     &rstack,
		IfStack:    &ifstack,
		Flags: Flags{
			"Immediate": true,
		},
		Words: []string{},
		Memory: Memory{
			intern:   map[int]int{},
			nextFree: 1,
		},
		StringBuffer: "",
		Output:       os.Stdout,
	}

	defineBuiltIns(&c)

	// load libraries
	for l := range libs {
		w, _ := c.Dictionary.GetWord("LOAD")
		c.StringBuffer = libs[l]
		err := w.Impl("")
		if err != nil {
			fmt.Fprintf(c.Output, "error in library %s: %v\n", libs[l], err)
		} else {
			fmt.Fprintf(c.Output, "loaded %s\n", libs[l])
		}
	}

	// set up liner
	line := liner.NewLiner()
	line.SetCtrlCAborts(true)
	line.SetCompleter(completer(dict))

	historyFile := historyFn()

	if f, err := os.Open(historyFile); err == nil {
		_, err := line.ReadHistory(f)
		if err != nil && *debug {
			fmt.Printf("error reading line history: %v", err)
		}
		f.Close()
	}

	defer func() {
		if f, err := os.Create(historyFile); err != nil {
			if *debug {
				fmt.Printf("Error writing history file: %v", err)
			}
		} else {
			line.WriteHistory(f)
			f.Close()
		}
		line.Close()
	}()

	// Welcome banner
	fmt.Print("prosper\n")

	// read loop
	for {
		p := "> "
		if !c.Flags["Immediate"] {
			p = "    "
		}

		// read line
		l, err := line.Prompt(p)
		if err == liner.ErrPromptAborted {
			fmt.Println("ctrl-C caught (try BYE)")
			continue
		} else if err != nil {
			fmt.Println(err.Error())
			os.Exit(1)
		}

		// parse line
		l = strings.TrimSpace(l)
		line.AppendHistory(l)
		err = c.Eval(l + " ") // append a space to make sure we always close out our parse loop
		if errors.Is(err, ErrExit) {
			fmt.Printf("bye\n")
			break
		} else if err != nil {
			fmt.Printf("error in evaluation: %v\n", err)
		} else if c.Flags["Immediate"] {
			fmt.Print("ok\n")
		}
	}
}

func defineBuiltIns(c *Context) {
	b := &Builtins{}
	// word definitions
	c.Dictionary.AddWord(":", Word{Name: ":", Impl: b.Colon(c)})
	c.Dictionary.AddWord(";", Word{Name: ";", Impl: b.Semicolon(c), Immediate: true})
	// comments and strings
	c.Dictionary.AddWord("(", Word{Name: "(", Impl: b.OpenComment(c), Immediate: true})
	c.Dictionary.AddWord(")", Word{Name: ")", Impl: b.CloseComment(c), Immediate: true})
	c.Dictionary.AddWord(`\`, Word{Name: `\`, Impl: b.EOLComment(c), Immediate: true})
	c.Dictionary.AddWord(`."`, Word{Name: `."`, Impl: b.OpenQuote(c.Output, c, '"')})
	c.Dictionary.AddWord(`"`, Word{Name: `"`, Impl: b.CloseQuote(c)})
	c.Dictionary.AddWord(`.(`, Word{Name: `.(`, Impl: b.OpenQuote(c.Output, c, ')'), Immediate: true})
	c.Dictionary.AddWord(`S"`, Word{Name: `S"`, Impl: b.StringBuffer(c, '"')})
	c.Dictionary.AddWord("LOAD", Word{Name: "LOAD", Impl: b.Load(c)})
	// math
	c.Dictionary.AddWord("+", Word{Name: "+", Impl: b.Add(c.Stack)})
	c.Dictionary.AddWord("-", Word{Name: "-", Impl: b.Sub(c.Stack)})
	c.Dictionary.AddWord("*", Word{Name: "*", Impl: b.Mul(c.Stack)})
	c.Dictionary.AddWord("/", Word{Name: "/", Impl: b.Div(c.Stack)})
	c.Dictionary.AddWord("MOD", Word{Name: "MOD", Impl: b.Mod(c.Stack)})
	c.Dictionary.AddWord("/MOD", Word{Name: "/MOD", Source: []string{"2DUP", "MOD", "ROT", "ROT", "/"}})
	c.Dictionary.AddWord("1+", Word{Name: "1+", Source: []string{"1", "+"}})
	c.Dictionary.AddWord("1-", Word{Name: "1-", Source: []string{"1", "-"}})
	c.Dictionary.AddWord("ABS", Word{Name: "ABS", Source: []string{"DUP", "0<", "IF", "NEGATE", "THEN"}})
	c.Dictionary.AddWord("NEGATE", Word{Name: "NEGATE", Source: []string{"-1", "*"}})
	c.Dictionary.AddWord("MAX", Word{Name: "MAX", Source: []string{"2DUP", "<", "IF", "SWAP", "THEN", "DROP"}})
	c.Dictionary.AddWord("MIN", Word{Name: "MIN", Source: []string{"2DUP", ">", "IF", "SWAP", "THEN", "DROP"}})
	// output
	c.Dictionary.AddWord(".", Word{Name: ".", Impl: b.Print(c.Output, c.Stack)})
	c.Dictionary.AddWord("EMIT", Word{Name: "EMIT", Impl: b.Emit(c.Output, c.Stack)})
	c.Dictionary.AddWord("CR", Word{Name: "CR", Source: []string{"10", "EMIT"}}) // emit a newline
	// logic
	c.Dictionary.AddWord("=", Word{Name: "=", Impl: b.Eq(c.Stack)})
	c.Dictionary.AddWord("0=", Word{Name: "0=", Source: []string{"0", "="}})
	c.Dictionary.AddWord("<>", Word{Name: "<>", Impl: b.NEq(c.Stack)})
	c.Dictionary.AddWord("0<>", Word{Name: "0<>", Source: []string{"0=", "0="}})
	c.Dictionary.AddWord(">", Word{Name: ">", Impl: b.Gt(c.Stack)})
	c.Dictionary.AddWord("<", Word{Name: "<", Impl: b.Lt(c.Stack)})
	c.Dictionary.AddWord(">=", Word{Name: ">=", Impl: b.GtEq(c.Stack)})
	c.Dictionary.AddWord("<=", Word{Name: "<=", Impl: b.LtEq(c.Stack)})
	c.Dictionary.AddWord("0<", Word{Name: "0<", Source: []string{"0", "<"}})
	c.Dictionary.AddWord("0>", Word{Name: "0>", Source: []string{"0", ">"}})
	// stack manipulation
	c.Dictionary.AddWord("DUP", Word{Name: "DUP", Impl: b.Dup(c.Stack)})
	c.Dictionary.AddWord("?DUP", Word{Name: "?DUP", Source: []string{"DUP", "0<>", "IF", "DUP", "THEN"}})
	c.Dictionary.AddWord("SWAP", Word{Name: "SWAP", Impl: b.Swap(c.Stack)})
	c.Dictionary.AddWord("OVER", Word{Name: "OVER", Impl: b.Over(c.Stack)})
	c.Dictionary.AddWord("DROP", Word{Name: "DROP", Impl: b.Drop(c.Stack)})
	c.Dictionary.AddWord("ROT", Word{Name: "ROT", Impl: b.Rot(c.Stack)})
	c.Dictionary.AddWord("PICK", Word{Name: "PICK", Impl: b.Pick(c.Stack)})
	c.Dictionary.AddWord("NIP", Word{Name: "NIP", Source: []string{"SWAP", "DROP"}})
	c.Dictionary.AddWord("TUCK", Word{Name: "TUCK", Source: []string{"SWAP", "OVER"}})
	// paired stack manipulation
	c.Dictionary.AddWord("2DROP", Word{Name: "2DROP", Source: []string{"DROP", "DROP"}})
	c.Dictionary.AddWord("2DUP", Word{Name: "2DUP", Source: []string{"OVER", "OVER"}})
	c.Dictionary.AddWord("2OVER", Word{Name: "2OVER", Source: []string{"3", "PICK", "3", "PICK"}})
	// memory access with variables and constants
	c.Dictionary.AddWord("VARIABLE", Word{Name: "VARIABLE", Impl: b.Variable(c)})
	c.Dictionary.AddWord("CONSTANT", Word{Name: "CONSTANT", Impl: b.Constant(c)})
	c.Dictionary.AddWord("!", Word{Name: "!", Impl: b.Store(c)})
	c.Dictionary.AddWord("@", Word{Name: "@", Impl: b.Fetch(c)})
	// debugging
	c.Dictionary.AddWord("WORDS", Word{Name: "WORDS", Impl: b.Words(c.Output, c.Dictionary)})
	c.Dictionary.AddWord("SEE", Word{Name: "SEE", Impl: b.See(c.Output, c.RStack, c.Dictionary)})
	c.Dictionary.AddWord("FLAGS", Word{Name: "FLAGS", Impl: b.Flags(c.Output, c)})
	c.Dictionary.AddWord(".S", Word{Name: ".S", Impl: b.Debug(c.Output, c.Stack)})
	c.Dictionary.AddWord(".R", Word{Name: ".R", Impl: b.Debug(c.Output, c.RStack)})
	c.Dictionary.AddWord(".I", Word{Name: ".I", Impl: b.Debug(c.Output, c.IfStack)})
	c.Dictionary.AddWord("DEPTH", Word{Name: "DEPTH", Impl: b.Depth(c.Stack)})
	c.Dictionary.AddWord("R>", Word{Name: "R>", Impl: b.RFrom(c.Stack, c.RStack)})
	c.Dictionary.AddWord(">R", Word{Name: ">R", Impl: b.ToR(c.Stack, c.RStack)})
	c.Dictionary.AddWord("R@", Word{Name: "R@", Impl: b.RFetch(c.Stack, c.RStack)})
	// branching
	c.Dictionary.AddWord("IF", Word{Name: "IF", Impl: b.If(c.Stack, c.IfStack), BranchCheck: true})
	c.Dictionary.AddWord("ELSE", Word{Name: "ELSE", Impl: b.Else(c.IfStack), BranchCheck: true})
	c.Dictionary.AddWord("THEN", Word{Name: "THEN", Impl: b.Then(c.IfStack), BranchCheck: true})
	c.Dictionary.AddWord("DO", Word{Name: "DO", Impl: b.Do(c.Stack, c.RStack)})
	c.Dictionary.AddWord("LOOP", Word{Name: "LOOP", Impl: b.Loop(c.Stack, c.RStack)})
	c.Dictionary.AddWord("I", Word{Name: "I", Impl: b.I(c.Stack, c.RStack)})
	// exit
	c.Dictionary.AddWord("BYE", Word{Name: "BYE", Impl: b.Quit()})
}