package tui

import (
	"strings"

	"github.com/lerko/nib/internal/db"
	"github.com/lerko/nib/internal/link"
)

type linkKind int

const (
	linkOutgoing linkKind = iota
	linkBacklink
)

type linkItem struct {
	text     string
	entityID string
	kind     linkKind
}

type linkPickerModel struct {
	items  []linkItem
	cursor int
}

func newLinkPicker(body string, backlinks []db.Backlink) linkPickerModel {
	var items []linkItem

	for _, lt := range link.ExtractLinks(body) {
		items = append(items, linkItem{text: lt, kind: linkOutgoing})
	}
	for _, bl := range backlinks {
		label := bl.Body
		if bl.Title != nil {
			label = *bl.Title
		} else if len(label) > 50 {
			label = label[:50] + "…"
		}
		items = append(items, linkItem{text: label, entityID: bl.EntityID, kind: linkBacklink})
	}

	return linkPickerModel{items: items}
}

func (lp linkPickerModel) selected() linkItem {
	if len(lp.items) == 0 || lp.cursor >= len(lp.items) {
		return linkItem{}
	}
	return lp.items[lp.cursor]
}

func (lp linkPickerModel) update(key string) linkPickerModel {
	switch key {
	case "up", "k":
		if lp.cursor > 0 {
			lp.cursor--
		}
	case "down", "j":
		if lp.cursor < len(lp.items)-1 {
			lp.cursor++
		}
	}
	return lp
}

func (lp linkPickerModel) view(width int) string {
	var b strings.Builder
	b.WriteString(titleStyle.Render("follow link") + "\n\n")

	if len(lp.items) == 0 {
		b.WriteString(hintDescStyle.Render("  no links or backlinks"))
		b.WriteString("\n\n")
		b.WriteString(helpStyle.Render("esc:back"))
		return b.String()
	}

	prevKind := linkKind(-1)
	for i, item := range lp.items {
		if item.kind != prevKind {
			if item.kind == linkOutgoing {
				b.WriteString(dateHeaderStyle.Render("── outgoing ──") + "\n")
			} else {
				b.WriteString(dateHeaderStyle.Render("── backlinks ──") + "\n")
			}
			prevKind = item.kind
		}

		var label string
		if item.kind == linkOutgoing {
			label = "[[" + item.text + "]]"
		} else {
			label = "← " + item.text
		}

		if i == lp.cursor {
			b.WriteString(selectedItemStyle.Render(" " + label))
		} else {
			b.WriteString(listItemStyle.Render(label))
		}
		b.WriteString("\n")
	}

	b.WriteString("\n")
	b.WriteString(helpStyle.Render("enter:follow  esc:back"))
	return b.String()
}