package tui

import (
	"fmt"
	"strings"
	"time"

	tea "github.com/charmbracelet/bubbletea"

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

type listModel struct {
	entities []*db.Entity
	cursor   int
	offset   int
	height   int
	width    int
}

func newListModel() listModel {
	return listModel{}
}

func (l *listModel) setEntities(entities []*db.Entity) {
	l.entities = entities
	if l.cursor >= len(entities) {
		l.cursor = max(0, len(entities)-1)
	}
}

func (l *listModel) setSize(width, height int) {
	l.width = width
	l.height = height
}

func (l listModel) selected() *db.Entity {
	if len(l.entities) == 0 || l.cursor >= len(l.entities) {
		return nil
	}
	return l.entities[l.cursor]
}

func (l listModel) update(msg tea.KeyMsg) listModel {
	switch msg.String() {
	case "up", "k":
		if l.cursor > 0 {
			l.cursor--
			if l.cursor < l.offset {
				l.offset = l.cursor
			}
		}
	case "down", "j":
		if l.cursor < len(l.entities)-1 {
			l.cursor++
			visible := l.visibleCount()
			if l.cursor >= l.offset+visible {
				l.offset = l.cursor - visible + 1
			}
		}
	case "home", "g":
		l.cursor = 0
		l.offset = 0
	case "end", "G":
		l.cursor = max(0, len(l.entities)-1)
		visible := l.visibleCount()
		if l.cursor >= visible {
			l.offset = l.cursor - visible + 1
		}
	case "pgup", "ctrl+u":
		l.cursor = max(0, l.cursor-l.visibleCount())
		if l.cursor < l.offset {
			l.offset = l.cursor
		}
	case "pgdown", "ctrl+d":
		l.cursor = min(len(l.entities)-1, l.cursor+l.visibleCount())
		visible := l.visibleCount()
		if l.cursor >= l.offset+visible {
			l.offset = l.cursor - visible + 1
		}
	}
	return l
}

func (l listModel) view(width int) string {
	if len(l.entities) == 0 {
		return statusStyle.Render("no entities")
	}

	groups := groupByDate(l.entities)

	type displayLine struct {
		text      string
		entityIdx int
		isHeader  bool
	}

	var lines []displayLine
	entityIdx := 0
	for _, g := range groups {
		lines = append(lines, displayLine{
			text:     dateHeaderStyle.Render("── " + g.label + " ──"),
			isHeader: true,
		})
		for _, e := range g.entities {
			line := renderEntity(e, width-4)
			lines = append(lines, displayLine{
				text:      line,
				entityIdx: entityIdx,
			})
			entityIdx++
		}
	}

	cursorLine := l.cursorDisplayLine(groups)
	visible := l.visibleCount()

	offset := 0
	if cursorLine >= visible {
		offset = cursorLine - visible + 1
	}

	var b strings.Builder
	end := min(offset+visible, len(lines))
	for i := offset; i < end; i++ {
		dl := lines[i]
		if dl.isHeader {
			b.WriteString(dl.text)
		} else if dl.entityIdx == l.cursor {
			b.WriteString(selectedItemStyle.Render(" " + dl.text))
		} else {
			b.WriteString(listItemStyle.Render(dl.text))
		}
		if i < end-1 {
			b.WriteString("\n")
		}
	}

	return b.String()
}

func (l listModel) cursorDisplayLine(groups []dateGroup) int {
	line := 0
	entityIdx := 0
	for _, g := range groups {
		line++
		for range g.entities {
			if entityIdx == l.cursor {
				return line
			}
			line++
			entityIdx++
		}
	}
	return 0
}

func (l listModel) visibleCount() int {
	if l.height <= 0 {
		return 20
	}
	return l.height
}

type dateGroup struct {
	label    string
	entities []*db.Entity
}

func groupByDate(entities []*db.Entity) []dateGroup {
	var groups []dateGroup
	var current *dateGroup

	for _, e := range entities {
		label := formatDateLabel(e.CreatedAt)
		if current == nil || current.label != label {
			if current != nil {
				groups = append(groups, *current)
			}
			current = &dateGroup{label: label}
		}
		current.entities = append(current.entities, e)
	}
	if current != nil {
		groups = append(groups, *current)
	}
	return groups
}

func formatDateLabel(t time.Time) string {
	return strings.ToLower(t.Format("Jan 2"))
}

func renderEntity(e *db.Entity, maxWidth int) string {
	glyphStr := display.DisplayGlyph(e.Glyph, e.CardType)
	style := glyphStyle
	if e.Glyph == db.GlyphTodo && e.CompletedAt != nil {
		glyphStr = "●"
		style = completedGlyphStyle
	}
	glyph := style.Render(glyphStr)

	id := idStyle.Render("[" + display.FormatID(e.ID) + "]")

	body := e.Body
	if e.Title != nil {
		body = *e.Title
	}

	var extras []string
	if e.Pinned {
		extras = append(extras, pinnedStyle.Render("•"))
	}
	if len(e.Tags) > 0 {
		tagParts := make([]string, len(e.Tags))
		for i, t := range e.Tags {
			tagParts[i] = tagStyle.Render("#" + t)
		}
		extras = append(extras, strings.Join(tagParts, " "))
	}

	extraStr := ""
	if len(extras) > 0 {
		extraStr = " " + strings.Join(extras, " ")
	}

	line := fmt.Sprintf("%s %s%s %s", glyph, body, extraStr, id)

	if maxWidth > 0 && len(stripAnsi(line)) > maxWidth {
		body = truncate(body, maxWidth-20)
		line = fmt.Sprintf("%s %s%s %s", glyph, body, extraStr, id)
	}

	return line
}

func truncate(s string, maxLen int) string {
	if maxLen <= 3 {
		return "…"
	}
	runes := []rune(s)
	if len(runes) <= maxLen {
		return s
	}
	return string(runes[:maxLen-1]) + "…"
}

func stripAnsi(s string) string {
	var b strings.Builder
	inEsc := false
	for _, r := range s {
		if r == '\x1b' {
			inEsc = true
			continue
		}
		if inEsc {
			if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') {
				inEsc = false
			}
			continue
		}
		b.WriteRune(r)
	}
	return b.String()
}