package main

import (
	"bytes"
	"errors"
	"fmt"
	"net/url"
	"slices"
	"strconv"
	"strings"
)

var (
	ErrEndOfTour      = errors.New("you've hit the end of the tour")
	ErrStartOfTour    = errors.New("you're at the start of the tour")
	ErrInvalidTourPos = errors.New("that's not a valid tour link")
)

type Tour struct {
	Index int
	Links []*url.URL
}

func parseURLs(state *BrowserState, defaultScheme, str string) ([]*url.URL, error) {
	urls := []*url.URL{}

	if str == "*" {
		for _, link := range state.Links {
			urls = append(urls, state.Url.ResolveReference(link.Target))
		}
		return urls, nil
	}

	if i := strings.IndexByte(str, '-'); i > 0 {
		start, e1 := strconv.Atoi(str[:i])
		end, e2 := strconv.Atoi(str[i+1:])
		if e1 == nil && e2 == nil && end >= start && start >= 0 && start < len(state.Links) && end < len(state.Links) {
			for _, link := range state.Links[start : end+1] {
				urls = append(urls, state.Url.ResolveReference(link.Target))
			}
			return urls, nil
		}
	}

	u, _, err := parseURL(str, state, defaultScheme)
	if err != nil {
		return nil, err
	}
	return []*url.URL{u}, nil
}

func TourAdd(state *BrowserState, targets []string) error {
	newurls := []*url.URL{}
	for _, target := range targets {
		urls, err := parseURLs(state, state.DefaultScheme, target)
		if err != nil {
			return err
		}
		newurls = append(newurls, urls...)
	}

	state.CurrentTour.Links = append(state.CurrentTour.Links, newurls...)

	if state.CurrentTour != &state.DefaultTour {
		return saveTours(state.NamedTours)
	}

	state.Modal = []byte(fmt.Sprintf("Added %d urls to the tour\n", len(newurls)))
	return Print(state)
}

func TourAddNext(state *BrowserState, targets []string) error {
	newurls := []*url.URL{}
	for _, target := range targets {
		urls, err := parseURLs(state, state.DefaultScheme, target)
		if err != nil {
			return err
		}
		newurls = append(newurls, urls...)
	}

	state.CurrentTour.Links = slices.Insert(
		state.CurrentTour.Links,
		state.CurrentTour.Index,
		newurls...,
	)

	if state.CurrentTour != &state.DefaultTour {
		return saveTours(state.NamedTours)
	}

	state.Modal = []byte(fmt.Sprintf("Added %d urls to go next on the tour\n", len(newurls)))
	return Print(state)
}

func TourShow(state *BrowserState) error {
	tour := state.CurrentTour
	buf := &bytes.Buffer{}
	for i, link := range tour.Links {
		mark := ""
		if i == tour.Index-1 {
			mark = "* "
		}
		if _, err := fmt.Fprintf(buf, "%s%d %s\n", mark, i, link.String()); err != nil {
			return err
		}
	}

	state.Modal = buf.Bytes()
	if len(state.Modal) == 0 {
		state.Modal = []byte("(empty)\n")
	}
	return Print(state)
}

func TourNext(state *BrowserState) error {
	tour := state.CurrentTour
	if tour.Index >= len(tour.Links) || len(tour.Links) == 0 {
		return ErrEndOfTour
	}
	page := tour.Links[tour.Index]
	tour.Index += 1

	return Navigate(state, page, -1)
}

func TourPrevious(state *BrowserState) error {
	tour := state.CurrentTour
	if tour.Index <= 0 {
		return ErrStartOfTour
	}
	tour.Index -= 1
	if tour.Index <= 0 {
		return ErrStartOfTour
	}
	page := tour.Links[tour.Index-1]

	return Navigate(state, page, -1)
}

func TourClear(state *BrowserState) error {
	state.CurrentTour.Index = 0
	state.CurrentTour.Links = nil

	if state.CurrentTour != &state.DefaultTour {
		return saveTours(state.NamedTours)
	}

	state.Modal = []byte("Tour is cleared\n")
	return Print(state)
}

func TourList(state *BrowserState) error {
	buf := &bytes.Buffer{}
	mark := ""
	if state.CurrentTour == &state.DefaultTour {
		mark = "* "
	}
	if _, err := fmt.Fprintf(buf, "%s(default): %d links\n", mark, len(state.DefaultTour.Links)); err != nil {
		return err
	}
	for name, tour := range state.NamedTours {
		mark = ""
		if tour == state.CurrentTour {
			mark = "* "
		}
		if _, err := fmt.Fprintf(buf, "%s%s: %d links\n", mark, name, len(tour.Links)); err != nil {
			return err
		}
	}

	state.Modal = buf.Bytes()
	return Print(state)
}

func TourGo(state *BrowserState, pos string) error {
	tour := state.CurrentTour

	i, _ := strconv.Atoi(pos)
	if i < 0 || i >= len(tour.Links) {
		return ErrInvalidTourPos
	}

	tour.Index = i + 1
	return Navigate(state, tour.Links[i], -1)
}

func TourSelect(state *BrowserState, name string) error {
	tourName, tour, err := findTour(state, name)
	if err != nil {
		return err
	}
	state.CurrentTour = tour

	state.Modal = []byte(fmt.Sprintf("Tour %s is now active\n", tourName))
	return Print(state)
}

func findTour(state *BrowserState, prefix string) (string, *Tour, error) {
	if prefix == "" {
		return "(default)", &state.DefaultTour, nil
	}

	found := 0
	var value *Tour
	var tourName string
	for name, tour := range state.NamedTours {
		if strings.HasPrefix(name, prefix) {
			found += 1
			value = tour
			tourName = name
		}
	}

	switch found {
	case 0:
		tour := &Tour{}
		state.NamedTours[prefix] = tour
		return prefix, tour, nil
	case 1:
		return tourName, value, nil
	default:
		return "", nil, fmt.Errorf("too ambiguous - found %d matching tours", found)
	}
}