package main

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

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

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")
	ErrSaveNeedsFilename  = errors.New("save requires a filename argument")
	ErrInvalidMarkArgs    = errors.New("mark what?")
	ErrInvalidTourArgs    = errors.New("tour what?")
	ErrOnlyTextGemini     = errors.New("that is only supported for text/gemini pages")
)

func ErrInvalidLink(invalidURL string) error {
	return invalidLinkErr(invalidURL)
}

type invalidLinkErr string

func (ie invalidLinkErr) Error() string {
	return fmt.Sprintf("that doesn't look like a valid URL: %s", string(ie))
}

func About(_ *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) error {
	if state.Url == nil || target.String() != state.Url.String() {
		pushHistory(state, target, navIndex)
	}
	state.Modal = nil

	return Reload(state)
}

func pushHistory(state *BrowserState, target *url.URL, navIndex int) {
	hist := state.History
	state.History = &History{
		Url:      target,
		Depth:    hist.Depth + 1,
		Back:     hist,
		NavIndex: navIndex,
	}
	hist.Forward = state.History

	purgeOldHistory(state)
}

func purgeOldHistory(state *BrowserState) {
	if state.Depth <= state.SavedHistoryDepth {
		return
	}

	d := state.SavedHistoryDepth
	h := state.History
	for d > 0 {
		h = h.Back
		d -= 1
	}

	h.Body = nil
	h.Formatted = ""
	h.Links = nil
}

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) 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)
	}

	tlsConf := tlsConfig(state)

	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 = upload(state, state.Url.String(), body, tlsConf)
		state.Url.Fragment = "prompt"
		if err != nil {
			return err
		}
	} else {
		response, err = fetch(state, urlStr, tlsConf)
		if err != nil {
			return err
		}
	}

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

				state.Url = response.Request.URL
				state.Url.RawQuery = url.QueryEscape(strings.TrimRight(line, "\n"))
				response, err = fetch(state, state.Url.String(), tlsConf)
				if err != nil {
					return err
				}
			case gemini.StatusSensitiveInput:
				line, err := state.Readline.ReadPassword(response.Meta.(string) + " ")
				if err != nil {
					return err
				}

				state.Url = response.Request.URL
				state.Url.RawQuery = url.QueryEscape(strings.TrimRight(string(line), "\n"))
				response, err = fetch(state, state.Url.String(), tlsConf)
				if err != nil {
					return err
				}
			case gemini.StatusSuccess:
				break outer
			default:
				return fmt.Errorf("gemini response %s: %s", gemini.StatusName(response.Status), response.Meta.(string))
			}
		}
	}

	state.DocType = docType(state.Url, response)
	state.Url = returnedURL(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, state.Config)
	if err != nil {
		return err
	}

	return HandleResource(state)
}

func returnedURL(requested *url.URL, response *sliderule.Response) *url.URL {
	_, gopherType := gopherURL(requested)
	if gopherType == 0 {
		return response.Request.URL
	}

	u := *response.Request.URL
	u.Path = "/" + string([]byte{byte(gopherType)}) + u.Path
	return &u
}

func requestCtx(timeout time.Duration) (context.Context, context.CancelFunc) {
	ctx := context.Background()
	if timeout > 0 {
		return context.WithTimeout(ctx, timeout)
	}
	return ctx, func() {}
}

func fetch(state *BrowserState, u string, tlsConf *tls.Config) (*sliderule.Response, error) {
	ctx, cancel := requestCtx(state.Timeout.Duration)
	defer cancel()

	tlsConf.ClientSessionCache = nil
	response, err := sliderule.NewClient(tlsConf).Fetch(ctx, u)
	var tofuErr *TOFUViolation

	if errors.As(err, &tofuErr) {
		state.Printer.PrintError(err.Error())
		state.Readline.SetPrompt("Trust new certificate instead (y/n)? [n] ")
		line, err := state.Readline.Readline()
		if err != nil {
			return nil, err
		}
		if line != "y" {
			return nil, tofuErr
		}

		tofuStore[tofuErr.domain] = tofuErr.got
		if err := saveTofuStore(tofuStore); err != nil {
			return nil, err
		}

		ctx, cancel = requestCtx(state.Timeout.Duration)
		defer cancel()
		return sliderule.NewClient(tlsConf).Fetch(ctx, u)
	} else if err != nil {
		return nil, err
	}
	return response, nil
}

func upload(state *BrowserState, u string, body io.Reader, tlsConf *tls.Config) (*sliderule.Response, error) {
	ctx, cancel := requestCtx(state.Timeout.Duration)
	defer cancel()

	tlsConf.ClientSessionCache = nil
	response, err := sliderule.NewClient(tlsConf).Upload(ctx, u, body)
	var tofuErr *TOFUViolation
	if errors.As(err, &tofuErr) {
		state.Printer.PrintError(err.Error())
		state.Readline.SetPrompt("Trust new certificate instead (y/n)? [n] ")
		line, err := state.Readline.Readline()
		if err != nil {
			return nil, err
		}
		if line != "y" {
			return nil, tofuErr
		}

		tofuStore[tofuErr.domain] = tofuErr.got
		if err := saveTofuStore(tofuStore); err != nil {
			return nil, err
		}

		ctx, cancel = requestCtx(state.Timeout.Duration)
		defer cancel()
		return sliderule.NewClient(tlsConf).Upload(ctx, u, body)
	} else if err != nil {
		return nil, err
	}
	return response, nil
}

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.Modal = nil
	state.History = state.Back

	if state.Body == nil {
		return Reload(state)
	}
	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 HandleResource(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 HandleResource(state)
}

func Next(state *BrowserState) 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)
}

func Previous(state *BrowserState) 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)
}

func Root(state *BrowserState, tilde bool) 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)
}

func Up(state *BrowserState) 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]
	u.RawQuery = ""
	u.Fragment = ""

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

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

	return Navigate(state, u, idx)
}

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(str)
		}

		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(str)
		}
		if i, err := strconv.Atoi(str[idx+2:]); err != nil {
			return nil, -1, ErrInvalidLink(str)
		} 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(str)
		}
		if u.Scheme == "" {
			u.Scheme = defaultScheme
		}
	}
	if state.Url != nil {
		u = state.Url.ResolveReference(u)
	}

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

	return u, i, nil
}

func print(state *BrowserState) error {
	if state.Modal != nil {
		defer func() { state.Modal = nil }()
		return state.Printer.PrintModal(state, state.Modal)
	}

	if state.Body == nil {
		return ErrMustBeOnAPage
	}

	if state.Quiet {
		return nil
	}

	return state.Printer.PrintPage(state, state.Formatted)
}

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

func HandleResource(state *BrowserState) error {
	if state.Modal != nil {
		return Print(state)
	}

	if handler, ok := state.Handlers[state.DocType]; ok {
		return Pipe(state, handler)
	}

	switch state.DocType {
	case "text/gemini", "text/x-gophermap", "text/plain":
		return print(state)
	}

	return Save(state, path.Base(state.Url.Path))
}

func Outline(state *BrowserState) error {
	if state.Body == nil {
		return ErrMustBeOnAPage
	}

	if state.DocType != "text/gemini" {
		return ErrOnlyTextGemini
	}

	gemdoc, err := gemtext.Parse(bytes.NewBuffer(state.Body))
	if err != nil {
		return err
	}

	b := &bytes.Buffer{}
	for _, line := range gemdoc {
		switch line.Type() {
		case gemtext.LineTypeHeading3, gemtext.LineTypeHeading2, gemtext.LineTypeHeading1:
			if _, err := b.Write(line.Raw()); err != nil {
				return err
			}
		}
	}

	formatted, _, err := parseGemtextDoc(b.Bytes(), state.SoftWrap)
	if err != nil {
		return err
	}

	state.Modal = []byte(formatted)
	if len(state.Modal) == 0 {
		state.Modal = []byte("No headers on the current page\n")
	}

	return Print(state)
}

func Links(state *BrowserState) 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(), state.Config)
	if err != nil {
		return err
	}
	state.Modal = []byte(formatted)
	if len(state.Links) == 0 {
		state.Modal = []byte("There are no links on the current page\n")
	}

	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) error {
	if state.Body == nil {
		return ErrMustBeOnAPage
	}
	if filename == "" {
		return ErrSaveNeedsFilename
	}

	p := filepath.Join(state.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
	}

	if err := os.WriteFile(p, state.Body, 0o644); err != nil {
		return err
	}
	state.Modal = []byte(fmt.Sprintf("Saved page to %s\n", p))
	return Print(state)
}

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

	return ErrInvalidMarkArgs
}

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

	return ErrInvalidTourArgs
}

func IdentityCmd(state *BrowserState, args []string) error {
	switch args[0] {
	case "create":
		return IdentityCreate(state, args[1])
	case "list":
		return IdentityList(state)
	case "delete":
		return IdentityDelete(state, args[1])
	case "use":
		switch args[2] {
		case "domain":
			return IdentityUseDomain(state, args[1], args[3])
		case "folder":
			return IdentityUseFolder(state, args[1], args[3])
		case "page":
			return IdentityUsePage(state, args[1], args[3])
		}
	}

	return ErrInvalidArgs
}

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()
}