package main

import (
	"bufio"
	"crypto/tls"
	"encoding/pem"
	"errors"
	"fmt"
	"net/url"
	"os"
	"path/filepath"
	"strings"
	"syscall"
	"time"

	"github.com/BurntSushi/toml"
)

type ConfigMain struct {
	DefaultScheme     string   `toml:"default_scheme"`
	SoftWrap          int      `toml:"soft_wrap"`
	DownloadFolder    string   `toml:"download_folder"`
	VimKeys           bool     `toml:"vim_keys"`
	Quiet             bool     `toml:"quiet"`
	Pager             string   `toml:"pager"`
	Timeout           duration `toml:"duration"`
	SavedHistoryDepth int      `toml:"saved_history_depth"`
}

type Config struct {
	ConfigMain `toml:"main"`

	Handlers map[string]string `toml:"handlers"`
}

type duration struct{ time.Duration }

func (d *duration) UnmarshalText(text []byte) error {
	var err error
	d.Duration, err = time.ParseDuration(string(text))
	return err
}

func getConfig() (*Config, error) {
	home := os.Getenv("HOME")
	path := os.Getenv("XDG_CONFIG_HOME")
	if path == "" {
		path = filepath.Join(home, ".config")
	}
	path = filepath.Join(path, "x-1", "config.toml")

	if err := ensurePath(path); err != nil {
		return nil, err
	}

	c := Config{
		ConfigMain: ConfigMain{
			VimKeys:        true,
			DefaultScheme:  "gemini",
			SoftWrap:       100,
			DownloadFolder: home,
			Quiet:          false,
			Pager:          "auto",
			Timeout: duration{
				time.Duration(10 * time.Second),
			},
			SavedHistoryDepth: 30,
		},
		Handlers: map[string]string{},
	}
	if _, err := toml.DecodeFile(path, &c); err != nil {
		return nil, err
	}
	if strings.HasPrefix(c.DownloadFolder, "~") {
		c.DownloadFolder = home + c.DownloadFolder[1:]
	}
	return &c, nil
}

func getMarks() (map[string]string, error) {
	path, err := marksFilePath()
	if err != nil {
		return nil, err
	}

	marks := make(map[string]string)

	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer func() { _ = f.Close() }()

	rdr := bufio.NewScanner(f)
	for rdr.Scan() {
		line := rdr.Text()
		name, target, _ := strings.Cut(line, ":")
		marks[name] = target
	}
	if err := rdr.Err(); err != nil {
		return nil, err
	}

	return marks, nil
}

func saveMarks(marks map[string]string) error {
	path, err := marksFilePath()
	if err != nil {
		return err
	}

	f, err := os.OpenFile(path, os.O_WRONLY|os.O_TRUNC, 0o600)
	if err != nil {
		return err
	}
	defer func() { _ = f.Close() }()

	for name, target := range marks {
		_, err := fmt.Fprintf(f, "%s:%s\n", name, target)
		if err != nil {
			return err
		}
	}

	return nil
}

func marksFilePath() (string, error) {
	return dataFilePath("marks")
}

func getTours() (map[string]*Tour, error) {
	path, err := toursFilePath()
	if err != nil {
		return nil, err
	}

	tours := make(map[string]*Tour)
	var current *Tour
	var currentName string

	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer func() { _ = f.Close() }()

	rdr := bufio.NewScanner(f)
	for rdr.Scan() {
		line := rdr.Text()
		if strings.HasSuffix(line, ":") {
			if currentName != "" {
				tours[currentName] = current
			}
			currentName = strings.TrimSuffix(line, ":")
			current = &Tour{}
		} else {
			u, err := url.Parse(line)
			if err != nil {
				return nil, err
			}
			current.Links = append(current.Links, u)
		}
	}
	if err := rdr.Err(); err != nil {
		return nil, err
	}

	if currentName != "" {
		tours[currentName] = current
	}

	return tours, nil
}

func saveTours(tours map[string]*Tour) error {
	path, err := toursFilePath()
	if err != nil {
		return err
	}

	f, err := os.OpenFile(path, os.O_WRONLY|os.O_TRUNC, 0o600)
	if err != nil {
		return err
	}
	defer func() { _ = f.Close() }()

	for name, tour := range tours {
		if len(tour.Links) == 0 {
			continue
		}

		if _, err := fmt.Fprintf(f, "%s:\n", name); err != nil {
			return err
		}

		for _, link := range tour.Links {
			if _, err := fmt.Fprintf(f, "%s\n", link.String()); err != nil {
				return err
			}
		}
	}

	return nil
}

func toursFilePath() (string, error) {
	return dataFilePath("tours")
}

func getTofuStore() error {
	tofuFilePath, err := dataFilePath("tofu")
	if err != nil {
		return err
	}

	tofuStore = map[string]string{}

	f, err := os.Open(tofuFilePath)
	if err != nil {
		return err
	}
	defer func() { _ = f.Close() }()

	rdr := bufio.NewScanner(f)
	for rdr.Scan() {
		domain, certhash, _ := strings.Cut(rdr.Text(), ":")
		tofuStore[domain] = certhash
	}
	if err := rdr.Err(); err != nil {
		return err
	}

	return nil
}

func saveTofuStore(store map[string]string) error {
	tofuFilePath, err := dataFilePath("tofu")
	if err != nil {
		return err
	}

	f, err := os.OpenFile(tofuFilePath, os.O_WRONLY|os.O_TRUNC, 0o600)
	if err != nil {
		return err
	}
	defer func() { _ = f.Close() }()

	for domain, certhash := range store {
		if _, err := fmt.Fprintf(f, "%s:%s\n", domain, certhash); err != nil {
			return err
		}
	}

	return nil
}

func dataFilePath(filename string) (string, error) {
	home := os.Getenv("HOME")
	path := os.Getenv("XDG_DATA_HOME")
	if path == "" {
		path = filepath.Join(home, ".local", "share")
	}
	path = filepath.Join(path, "x-1", filename)

	if err := ensurePath(path); err != nil {
		return "", err
	}

	return path, nil
}

func ensurePath(fpath string) error {
	if _, err := os.Stat(fpath); errors.Is(err, syscall.ENOENT) {
		if err := os.MkdirAll(filepath.Dir(fpath), 0o700); err != nil {
			return err
		}
		f, err := os.OpenFile(fpath, os.O_RDWR|os.O_CREATE, 0o600)
		if err != nil {
			return err
		}
		_ = f.Close()
	}
	return nil
}

func getIdentities() (Identities, error) {
	idents := Identities{
		ByName:   map[string]*tls.Config{},
		ByDomain: map[string]*tls.Config{},
		ByFolder: map[string]*tls.Config{},
		ByPage:   map[string]*tls.Config{},
	}

	manifest, err := dataFilePath("identities")
	if err != nil {
		return idents, err
	}

	f, err := os.Open(manifest)
	if err != nil {
		return idents, err
	}
	defer func() { _ = f.Close() }()

	var curident *tls.Config
	rdr := bufio.NewScanner(f)
	for rdr.Scan() {
		line := rdr.Text()
		if strings.HasPrefix(line, ":") {
			kind, location, _ := strings.Cut(line[1:], " ")
			switch kind {
			case "domain":
				idents.ByDomain[location] = curident
			case "folder":
				idents.ByFolder[location] = curident
			case "page":
				idents.ByPage[location] = curident
			}
		} else {
			name := strings.TrimSuffix(line, ":")
			curident, err = getIdentity(name)
			if err != nil {
				return idents, err
			}
			idents.ByName[name] = curident
		}
	}
	if err := rdr.Err(); err != nil {
		return idents, err
	}

	return idents, nil
}

func saveIdentities(idents Identities) error {
	manifest, err := dataFilePath("identities")
	if err != nil {
		return err
	}

	f, err := os.OpenFile(manifest, os.O_WRONLY|os.O_TRUNC, 0o600)
	if err != nil {
		return err
	}
	defer func() { _ = f.Close() }()

	for name, ident := range idents.ByName {
		if _, err := fmt.Fprintf(f, "%s:\n", name); err != nil {
			return err
		}

		for domain, id := range idents.ByDomain {
			if id != ident {
				continue
			}
			if _, err := fmt.Fprintf(f, ":domain %s\n", domain); err != nil {
				return err
			}
		}
		for folder, id := range idents.ByFolder {
			if id != ident {
				continue
			}
			if _, err := fmt.Fprintf(f, ":folder %s\n", folder); err != nil {
				return err
			}
		}
		for page, id := range idents.ByPage {
			if id != ident {
				continue
			}
			if _, err := fmt.Fprintf(f, ":page %s\n", page); err != nil {
				return err
			}
		}
	}

	return nil
}

func getIdentity(name string) (*tls.Config, error) {
	fpath, err := dataFilePath("ident/" + name)
	if err != nil {
		return nil, err
	}

	cert, err := tls.LoadX509KeyPair(fpath, fpath)
	if err != nil {
		return nil, err
	}

	return identityForCert(cert), nil
}

func saveIdentity(name string, privkeyDER, certDER []byte) (string, error) {
	fpath, err := dataFilePath("ident/" + name)
	if err != nil {
		return "", err
	}

	f, err := os.OpenFile(fpath, os.O_WRONLY|os.O_TRUNC, 0o600)
	if err != nil {
		return "", err
	}
	defer func() { _ = f.Close() }()

	if err := pem.Encode(f, &pem.Block{Type: "PRIVATE KEY", Bytes: privkeyDER}); err != nil {
		return "", err
	}
	if err := pem.Encode(f, &pem.Block{Type: "CERTIFICATE", Bytes: certDER}); err != nil {
		return "", err
	}

	return fpath, nil
}

func removeIdentity(name string) error {
	fpath, err := dataFilePath("ident/" + name)
	if err != nil {
		return err
	}
	return os.Remove(fpath)
}