package main

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"net/url"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"syscall"

	"tildegit.org/tjp/sliderule"
	"tildegit.org/tjp/sliderule/gemini"
	"tildegit.org/tjp/sliderule/gopher"
)

var client sliderule.Client

func init() {
	client = sliderule.NewClient(nil)
}

var (
	ErrMustBeOnAPage      = errors.New("you must be on a page to do that, use the \"go\" command first")
	ErrNoPreviousHistory  = errors.New("there is no previous page in the history")
	ErrNoNextHistory      = errors.New("there is no page to go forward to")
	ErrOnLastLink         = errors.New("already on the last link")
	ErrOnFirstLink        = errors.New("already on the first link")
	ErrCantMoveRelative   = errors.New("next/previous only work after navigating to a link on a page")
	ErrAlreadyAtTop       = errors.New("already at the site root")
	ErrInvalidNumericLink = errors.New("no link with that number")
	ErrInvalidLink        = errors.New("that doesn't look like a valid URL")
	ErrSaveNeedsFilename  = errors.New("save requires a filename argument")
	ErrInvalidMarkArgs    = errors.New("mark what?")
	ErrInvalidTourArgs    = errors.New("tour what?")
)

func About(state *BrowserState) error {
	_, err := fmt.Println(`
                                                                                ...
                                                                              *=:::.
                                                     ---======-              -+-.....
                                                     .#@@@@@@@=             .+=-:....:++
                                                    +@@@@@@@@#              :-::.. ...*+
                                                  :%@@@@@@@@@.             =*+++==:....
                                                .*@@@@@@@@@@=            -#%###**++-:..
                                               -@@@@@@@@@@@%     .::-=*#@@#*#@@@@@@@%-.
                              ..:::----=====++#@@@@@@@@@@@@%%%@@@@@@@@@@%%#**@@@@@@@=
                     .-+#%%@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@-
                    =*@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@##%@@*%@@@@@@@@@@-  ..
           -+*.     .#@@@@@@@@@@@@@@@@@@@@@@@@@@@%@@@@@@%%%%###- =- .=.==----==--:...
...:::::=#@@@@#**+*##@@@#*%%%%%%%%##############******+==-:-=-:.-==-:..   ...
         .:.:-==++++====::-----::---:-+%@@@@@@@@@@@@@#-...
                   .  ...............=@@@@@@@@@@@@@@+....
                                    -@@@@@@@@@@@@@#.
                                   -@@@@@@@@@@@@%-
                                  -@@%%##@@@@@@=
                                 =%++*=-=%@@@*.
                                =--*%%%::#@#:
                               *@+=#-+*%@%-
                             .*%****###@+.
                   ::..:::.::*@@@%%%%%#:

x-1 is a browser for small web protocols gemini, gopher, finger, spartan, and nex.
It also has very limited support for HTTP[S].

It was written by TJP and released to the public domain.
`[1:])
	return err
}

func Navigate(state *BrowserState, target *url.URL, navIndex int, conf *Config) error {
	hist := state.History

	if hist.Url == nil || target.String() != hist.Url.String() {
		state.History = &History{
			Url:      target,
			Depth:    hist.Depth + 1,
			Back:     hist,
			NavIndex: navIndex,
		}
		hist.Forward = state.History
	}
	state.Modal = nil

	return Reload(state, conf)
}

func gopherURL(u *url.URL) (string, sliderule.Status) {
	if u.Scheme != "gopher" || len(u.Path) < 2 || !strings.HasPrefix(u.Path, "/") {
		return u.String(), 0
	}
	itemType := u.Path[1]
	clone := *u
	clone.Path = u.Path[2:]
	return clone.String(), sliderule.Status(itemType)
}

func Reload(state *BrowserState, conf *Config) error {
	if state.Url == nil {
		return ErrMustBeOnAPage
	}

	urlStr, itemType := gopherURL(state.Url)
	if itemType == gopher.SearchType && state.Url.RawQuery == "" {
		state.Readline.SetPrompt("query: ")
		line, err := state.Readline.Readline()
		if err != nil {
			return err
		}

		state.Url.RawQuery = url.QueryEscape(strings.TrimRight(line, "\n"))
		urlStr, _ = gopherURL(state.Url)
	}

	var response *sliderule.Response
	var err error
	if state.Url.Scheme == "spartan" && state.Url.Fragment == "prompt" {
		input, err := externalMessage()
		if err != nil {
			return err
		}
		body := io.LimitReader(bytes.NewBuffer(input), int64(len(input)))

		state.Url.Fragment = ""
		response, err = client.Upload(state.Url.String(), body)
		state.Url.Fragment = "prompt"
		if err != nil {
			return err
		}
	} else {
		response, err = client.Fetch(urlStr)
		if err != nil {
			return err
		}
	}

	if state.Url.Scheme == "gemini" {
		switch response.Status {
		case gemini.StatusInput:
			state.Readline.SetPrompt("input: ")
			line, err := state.Readline.Readline()
			if err != nil {
				return err
			}

			state.Url.RawQuery = url.QueryEscape(strings.TrimRight(line, "\n"))
			response, err = client.Fetch(state.Url.String())
			if err != nil {
				return err
			}
		case gemini.StatusSensitiveInput:
			line, err := state.Readline.ReadPassword("password: ")
			if err != nil {
				return err
			}

			state.Url.RawQuery = url.QueryEscape(strings.TrimRight(string(line), "\n"))
			response, err = client.Fetch(state.Url.String())
			if err != nil {
				return err
			}
		}
	}

	state.DocType = docType(state.Url, response)
	state.Body, err = io.ReadAll(response.Body)
	if err != nil {
		return err
	}

	state.Formatted, state.Links, err = parseDoc(state.DocType, state.Body, conf)
	if err != nil {
		return err
	}

	return print(state)
}

func externalMessage() ([]byte, error) {
	tmpf, err := os.CreateTemp("", "*")
	if err != nil {
		return nil, err
	}
	defer func() { _ = os.Remove(tmpf.Name()) }()

	prompt := []byte("# enter input below (this line will be ignored)\n")

	err = (func() error {
		defer func() { _ = tmpf.Close() }()

		if _, err := tmpf.Write(prompt); err != nil {
			return err
		}

		return nil
	}())
	if err != nil {
		return nil, err
	}

	editor := os.Getenv("EDITOR")
	if editor == "" {
		editor = "vi"
	}
	editor, err = exec.LookPath(editor)
	if err != nil {
		return nil, err
	}

	cmd := exec.Command(editor, tmpf.Name())
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Run(); err != nil {
		return nil, err
	}

	tmpf, err = os.Open(tmpf.Name())
	if err != nil {
		return nil, err
	}
	defer func() { _ = tmpf.Close() }()

	buf, err := io.ReadAll(tmpf)
	if err != nil {
		return nil, err
	}

	return bytes.TrimPrefix(buf, prompt), nil
}

func back(state *BrowserState) error {
	if state.Back == nil {
		return ErrNoPreviousHistory
	}
	state.History = state.Back
	state.Modal = nil
	return nil
}

func Back(state *BrowserState, num int) error {
	for i := 0; i < num; i += 1 {
		if err := back(state); err != nil {
			return err
		}
	}
	return print(state)
}

func Forward(state *BrowserState, num int) error {
	for i := 0; i < num; i += 1 {
		if state.Forward == nil {
			return ErrNoNextHistory
		}
		state.History = state.Forward
	}
	state.Modal = nil

	return print(state)
}

func Next(state *BrowserState, conf *Config) error {
	switch state.NavIndex {
	case -1:
		return ErrCantMoveRelative
	case len(state.Back.Links) - 1:
		return ErrOnLastLink
	}

	index := state.NavIndex + 1

	if err := back(state); err != nil {
		return err
	}

	u := state.Url.ResolveReference(state.Links[index].Target)

	return Navigate(state, u, index, conf)
}

func Previous(state *BrowserState, conf *Config) error {
	switch state.NavIndex {
	case -1:
		return ErrCantMoveRelative
	case 0:
		return ErrOnFirstLink
	}

	index := state.NavIndex - 1

	if err := back(state); err != nil {
		return err
	}

	u := state.Url.ResolveReference(state.Links[index].Target)

	return Navigate(state, u, index, conf)
}

func Root(state *BrowserState, tilde bool, conf *Config) error {
	if state.Url == nil {
		return ErrMustBeOnAPage
	}

	u := *state.Url
	u.RawQuery = ""
	u.Fragment = ""

	base := "/"
	if u.Scheme == "gopher" {
		base = "/1/"
	}

	if tilde && strings.HasPrefix(u.Path, "/~") {
		u.Path = base + strings.SplitN(u.Path, "/", 3)[1] + "/"
	} else {
		u.Path = base
	}

	return Navigate(state, &u, -1, conf)
}

func Up(state *BrowserState, conf *Config) error {
	if state.Url == nil {
		return ErrMustBeOnAPage
	}

	u := *state.Url
	u.Path = strings.TrimSuffix(u.Path, "/")
	if u.Path == "" {
		return ErrAlreadyAtTop
	}

	u.Path = u.Path[:strings.LastIndex(u.Path, "/")+1]

	return Navigate(state, &u, -1, conf)
}

func Go(state *BrowserState, dest string, conf *Config) error {
	u, idx, err := parseURL(dest, state, conf.DefaultScheme)
	if err != nil {
		return err
	}

	return Navigate(state, u, idx, conf)
}

func parseURL(str string, state *BrowserState, defaultScheme string) (*url.URL, int, error) {
	if str == "." {
		if state.Url == nil {
			return nil, -1, ErrMustBeOnAPage
		}
		return state.Url, -1, nil
	}

	if strings.HasPrefix(str, "m:") {
		_, target, err := findMark(state, str[2:])
		if err != nil {
			return nil, -1, err
		}
		str = target
	} else if strings.HasPrefix(str, "t:") {
		i, err := strconv.Atoi(str[2:])
		if err != nil {
			return nil, -1, ErrInvalidLink
		}

		if i < 0 || i >= len(state.CurrentTour.Links) {
			return nil, -1, ErrInvalidTourPos
		}
		return state.CurrentTour.Links[i], -1, nil
	} else if strings.HasPrefix(str, "t[") {
		idx := strings.IndexByte(str, ']')
		if idx < 0 || idx >= len(str)-2 || str[idx+1] != ':' {
			return nil, -1, ErrInvalidLink
		}
		if i, err := strconv.Atoi(str[idx+2:]); err != nil {
			return nil, -1, ErrInvalidLink
		} else {
			tour, err := findTour(state, str[2:idx])
			if err != nil {
				return nil, -1, err
			}

			if i < 0 || i >= len(tour.Links) {
				return nil, -1, ErrInvalidTourPos
			}
			return tour.Links[i], -1, nil
		}
	}

	var u *url.URL
	i, err := strconv.Atoi(str)
	if err == nil {
		if len(state.Links) <= i {
			return nil, -1, ErrInvalidNumericLink
		}
		u = state.Links[i].Target
		if state.Links[i].Prompt {
			u.Fragment = "prompt"
		}
	} else {
		i = -1
		u, err = url.Parse(str)
		if err != nil {
			return nil, -1, ErrInvalidLink
		}
		if u.Scheme == "" {
			u.Scheme = defaultScheme
		}
	}
	if state.Url != nil {
		u = state.Url.ResolveReference(u)
	}

	if u.Hostname() == "" {
		return nil, -1, ErrInvalidLink
	}

	return u, i, nil
}

func print(state *BrowserState) error {
	if state.Quiet {
		return nil
	}

	defer func() { state.Modal = nil }()

	if state.Body == nil && state.Modal == nil {
		return ErrMustBeOnAPage
	}
	out := []byte(state.Formatted)
	if state.Modal != nil {
		out = state.Modal
	}

	if state.Modal != nil || state.Pager == "never" {
		_, err := os.Stdout.Write(out)
		return err
	}

	lessarg := []string{}
	switch state.Pager {
	case "auto":
		lessarg = []string{"-F"}
		fallthrough
	case "always":
		less, err := exec.LookPath("less")
		if err != nil {
			return err
		}
		cmd := exec.Command(less, lessarg...)
		cmd.Stdin = bytes.NewBuffer(out)
		cmd.Stdout = os.Stdout
		cmd.Stderr = os.Stderr
		return cmd.Run()
	}

	return errors.New("invalid 'pager' value in configuration")
}

func Print(state *BrowserState) error {
	q := state.Quiet
	defer func() { state.Quiet = q }()
	state.Quiet = false
	return print(state)
}

func Links(state *BrowserState, conf *Config) error {
	if state.Links == nil {
		return ErrMustBeOnAPage
	}

	buf := &bytes.Buffer{}
	for _, link := range state.Links {
		fmt.Fprintf(buf, "=> %s %s\n", link.Target.String(), link.Text)
	}
	formatted, _, err := parseDoc("text/gemini", buf.Bytes(), conf)
	if err != nil {
		return err
	}
	state.Modal = []byte(formatted)

	return Print(state)
}

func HistoryCmd(state *BrowserState) error {
	if state.History == nil {
		return ErrMustBeOnAPage
	}

	h := state.History
	i := 0
	for h.Forward != nil {
		h = h.Forward
		i += 1
	}

	buf := &bytes.Buffer{}
	j := 0
	for h.Url != nil {
		mark := ""
		if j == i {
			mark = "* "
		}
		fmt.Fprintf(buf, "%s%s\n", mark, h.Url.String())
		j += 1
		h = h.Back
	}
	state.Modal = buf.Bytes()

	return Print(state)
}

func Save(state *BrowserState, filename string, conf *Config) error {
	if state.Body == nil {
		return ErrMustBeOnAPage
	}
	if filename == "" {
		return ErrSaveNeedsFilename
	}

	p := filepath.Join(conf.DownloadFolder, filename)
	_, err := os.Stat(p)
	pbase := p
	i := 1
	for !errors.Is(err, syscall.ENOENT) {
		p = pbase + "-" + strconv.Itoa(i)
		_, err = os.Stat(p)
		i += 1
	}

	return os.WriteFile(p, state.Body, 0o644)
}

func Mark(state *BrowserState, args []string, conf *Config) error {
	switch args[0] {
	case "add":
		return MarkAdd(state, conf, args[1], args[2])
	case "go":
		return MarkGo(state, conf, args[1])
	case "list":
		return MarkList(state)
	case "delete":
		return MarkDelete(state, args[1])
	}

	return ErrInvalidMarkArgs
}

func TourCmd(state *BrowserState, args []string, conf *Config) error {
	switch args[0] {
	case "add":
		if args[1] == "next" {
			return TourAddNext(state, conf, args[2:])
		}
		return TourAdd(state, conf, args[1:])
	case "show":
		return TourShow(state)
	case "select":
		return TourSelect(state, args[1])
	case "next":
		return TourNext(state, conf)
	case "previous":
		return TourPrevious(state, conf)
	case "clear":
		return TourClear(state)
	case "list":
		return TourList(state)
	case "go":
		return TourGo(state, conf, args[1])
	}

	return ErrInvalidTourArgs
}

func Pipe(state *BrowserState, cmdStr string) error {
	if state.Body == nil {
		return ErrMustBeOnAPage
	}

	sh, err := exec.LookPath("sh")
	if err != nil {
		return err
	}

	cmd := exec.Command(sh, "-c", cmdStr)
	cmd.Stdin = bytes.NewBuffer(state.Body)

	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	return cmd.Run()
}