package html

import (
	"maps"
	"slices"
	"strconv"
	"strings"
)

// responsive.go: Responsive wraps multiple Layout variants for breakpoint-aware rendering.
// Example: NewResponsive().Variant("desktop", NewLayout("C").C(Raw("main"))).
// Each variant is rendered inside a container with data-variant for CSS targeting.
type Responsive struct {
	variants []responsiveVariant
	attrs    map[string]string
}

type responsiveVariant struct {
	name   string
	layout *Layout
}

// responsive.go: NewResponsive creates a new multi-variant responsive compositor.
// Example: r := NewResponsive().
func NewResponsive() *Responsive {
	return &Responsive{
		attrs: make(map[string]string),
	}
}

func (r *Responsive) setAttr(key, value string) {
	if r == nil {
		return
	}
	if r.attrs == nil {
		r.attrs = make(map[string]string)
	}
	r.attrs[key] = value
}

// escapeCSSString escapes a string for safe use inside a double-quoted CSS
// attribute selector.
func escapeCSSString(s string) string {
	var b strings.Builder
	for _, r := range s {
		switch r {
		case '\\', '"':
			b.WriteByte('\\')
			b.WriteRune(r)
		case '\n':
			b.WriteString(`\a `)
		case '\r':
			b.WriteString(`\d `)
		case '\f':
			b.WriteString(`\c `)
		default:
			if r < 0x20 || r == 0x7f {
				b.WriteByte('\\')
				b.WriteString(strings.ToLower(strconv.FormatInt(int64(r), 16)))
				b.WriteByte(' ')
				continue
			}
			b.WriteRune(r)
		}
	}
	return b.String()
}

// responsive.go: VariantSelector returns a CSS attribute selector for a named responsive variant.
// Example: VariantSelector("desktop") returns [data-variant="desktop"].
func VariantSelector(name string) string {
	return `[data-variant="` + escapeCSSString(name) + `"]`
}

// responsive.go: ScopeVariant prefixes a selector so it only matches elements inside the
// named responsive variant.
// Example: ScopeVariant("desktop", ".nav").
func ScopeVariant(name, selector string) string {
	scope := VariantSelector(name)
	if selector == "" {
		return scope
	}

	parts := splitSelectorList(selector)
	scoped := make([]string, 0, len(parts))
	for i := range parts {
		part := strings.TrimSpace(parts[i])
		if part == "" {
			continue
		}
		scoped = append(scoped, scope+" "+part)
	}
	if len(scoped) == 0 {
		return scope
	}
	return strings.Join(scoped, ", ")
}

// splitSelectorList splits a CSS selector list on top-level commas only.
// Commas inside brackets, parentheses, braces, or quoted strings are preserved.
func splitSelectorList(selector string) []string {
	if selector == "" {
		return nil
	}

	parts := make([]string, 0, 1)
	var b strings.Builder
	var quote rune
	escaped := false
	depthParen := 0
	depthBracket := 0
	depthBrace := 0

	for _, r := range selector {
		if escaped {
			b.WriteRune(r)
			escaped = false
			continue
		}

		if r == '\\' {
			b.WriteRune(r)
			escaped = true
			continue
		}

		switch {
		case quote != 0:
			b.WriteRune(r)
			if r == quote {
				quote = 0
			}
		case r == '"' || r == '\'':
			quote = r
			b.WriteRune(r)
		case r == '(':
			depthParen++
			b.WriteRune(r)
		case r == ')':
			if depthParen > 0 {
				depthParen--
			}
			b.WriteRune(r)
		case r == '[':
			depthBracket++
			b.WriteRune(r)
		case r == ']':
			if depthBracket > 0 {
				depthBracket--
			}
			b.WriteRune(r)
		case r == '{':
			depthBrace++
			b.WriteRune(r)
		case r == '}':
			if depthBrace > 0 {
				depthBrace--
			}
			b.WriteRune(r)
		case r == ',' && depthParen == 0 && depthBracket == 0 && depthBrace == 0:
			parts = append(parts, b.String())
			b.Reset()
		default:
			b.WriteRune(r)
		}
	}

	parts = append(parts, b.String())
	return parts
}

// responsive.go: Variant adds a named layout variant (e.g., "desktop", "tablet", "mobile").
// Example: r.Variant("mobile", NewLayout("C").C(Raw("body"))).
// Variants render in insertion order.
func (r *Responsive) Variant(name string, layout *Layout) *Responsive {
	if r == nil {
		return nil
	}
	r.variants = append(r.variants, responsiveVariant{name: name, layout: layout})
	return r
}

// responsive.go: Render produces HTML with each variant in a data-variant container.
// Example: NewResponsive().Variant("desktop", NewLayout("C")).Render(NewContext()).
func (r *Responsive) Render(ctx *Context) string {
	return r.renderWithPath(ctx, "")
}

func (r *Responsive) cloneNode() Node {
	if r == nil {
		return (*Responsive)(nil)
	}

	clone := *r
	if r.attrs != nil {
		clone.attrs = maps.Clone(r.attrs)
	}
	if r.variants != nil {
		clone.variants = make([]responsiveVariant, len(r.variants))
		for i := range r.variants {
			clone.variants[i] = r.variants[i]
			if r.variants[i].layout != nil {
				if layout, ok := cloneNode(r.variants[i].layout).(*Layout); ok {
					clone.variants[i].layout = layout
				}
			}
		}
	}
	return &clone
}

func (r *Responsive) renderWithPath(ctx *Context, path string) string {
	if r == nil {
		return ""
	}
	ctx = normaliseContext(ctx)

	var b strings.Builder
	for _, v := range r.variants {
		b.WriteString(`<div`)
		if len(r.attrs) > 0 {
			keys := slices.Collect(maps.Keys(r.attrs))
			slices.Sort(keys)
			for _, key := range keys {
				if key == "data-variant" {
					continue
				}
				b.WriteByte(' ')
				b.WriteString(escapeHTML(key))
				b.WriteString(`="`)
				b.WriteString(escapeAttr(r.attrs[key]))
				b.WriteByte('"')
			}
		}
		b.WriteString(` data-variant="`)
		b.WriteString(escapeAttr(v.name))
		b.WriteString(`">`)
		b.WriteString(renderNodeWithPath(v.layout, ctx, path))
		b.WriteString(`</div>`)
	}
	return b.String()
}