package tui

import (
	"strings"

	"github.com/charmbracelet/lipgloss"
	"github.com/lerko/nib/internal/db"
)

const maxSuggestions = 5

type autocompleteModel struct {
	suggestions []string
	cursor      int
	active      bool
	prefix      string
	tokenStart  int
	tokenEnd    int
}

func (a *autocompleteModel) moveUp() {
	if a.cursor > 0 {
		a.cursor--
	}
}

func (a *autocompleteModel) moveDown() {
	if a.cursor < len(a.suggestions)-1 {
		a.cursor++
	}
}

func (a autocompleteModel) selected() string {
	if len(a.suggestions) == 0 || a.cursor >= len(a.suggestions) {
		return ""
	}
	return a.suggestions[a.cursor]
}

func (a autocompleteModel) visibleCount() int {
	if len(a.suggestions) > maxSuggestions {
		return maxSuggestions
	}
	return len(a.suggestions)
}

func (a autocompleteModel) view(width int) string {
	if !a.active || len(a.suggestions) == 0 {
		return ""
	}

	var b strings.Builder
	n := a.visibleCount()
	for i := 0; i < n; i++ {
		tag := "#" + a.suggestions[i]
		if i == a.cursor {
			b.WriteString(acSelectedStyle.Render(" › " + tag))
		} else {
			b.WriteString(acItemStyle.Render("   " + tag))
		}
		if i < n-1 {
			b.WriteString("\n")
		}
	}
	if len(a.suggestions) > maxSuggestions {
		b.WriteString("\n")
		b.WriteString(acItemStyle.Render("   …"))
	}

	box := lipgloss.NewStyle().
		Width(min(30, width)).
		Render(b.String())
	return box
}

func tagTokenAtCursor(val string, cursorPos int) (tokenStart, tokenEnd int, prefix string, ok bool) {
	if cursorPos > len(val) {
		cursorPos = len(val)
	}

	start := cursorPos
	for start > 0 && val[start-1] != ' ' {
		start--
	}

	if start >= len(val) || val[start] != '#' {
		return 0, 0, "", false
	}

	end := cursorPos
	for end < len(val) && val[end] != ' ' {
		end++
	}

	prefix = strings.ToLower(val[start+1 : cursorPos])
	return start, end, prefix, true
}

func filterTagSuggestions(tags []db.TagCount, prefix string) []string {
	if prefix == "" {
		return nil
	}
	prefix = strings.ToLower(prefix)
	var result []string
	for _, tc := range tags {
		lower := strings.ToLower(tc.Tag)
		if strings.HasPrefix(lower, prefix) && lower != prefix {
			result = append(result, tc.Tag)
		}
	}
	return result
}