package style

import "image/color"
import "git.tebibyte.media/tomo/tomo"

// Style can apply a visual style to different objects.
type Style struct {
	// Rules determines which styles get applied to which Objects.
	Rules []Rule

	// Colors maps tomo.Color values to color.RGBA values.
	Colors map[tomo.Color] color.Color
}

// Rule describes under what circumstances should certain style attributes be
// active.
type Rule struct {
	Role tomo.Role
	Tags []string
	Set  AttrSet
}

// Ru is shorthand for creating a rule structure
func Ru (set AttrSet, role tomo.Role, tags ...string) Rule {
	return Rule {
		Role: role,
		Tags: tags,
		Set:  set,
	}
}

// AttrSet is a set of attributes wherein only one/zero of each attribute type
// can exist. It is keyed by the AttrKind of each attribute and must not be
// modified directly.
type AttrSet map[tomo.AttrKind] tomo.Attr

// AS builds an AttrSet out of a vararg list of Attr values. If multiple Attrs
// of the same kind are specified, the last one will override the others.
func AS (attrs ...tomo.Attr) AttrSet {
	set := AttrSet { }
	set.Add(attrs...)
	return set
}

// Add adds attributes to the set.
func (this AttrSet) Add (attrs ...tomo.Attr) {
	for _, attr := range attrs {
		this[attr.Kind()] = attr
	}
}

// MergeUnder takes attributes from another set and adds them if they don't
// already exist in this one.
func (this AttrSet) MergeUnder (other AttrSet) {
	if other == nil { return }
	for _, attr := range other {
		if _, exists := this[attr.Kind()]; !exists {
			this.Add(attr)
		}
	}
}

// MergeOver takes attributes from another set and adds them, overriding this
// one.
func (this AttrSet) MergeOver (other AttrSet) {
	if other == nil { return }
	for _, attr := range other {
		this.Add(attr)
	}
}