/**
 * Color resolution for charts. Tone names map to theme CSS vars so charts are
 * automatically theme + dark-mode aware; any raw CSS color passes through.
 */
import type { ThemeType } from '../../../types'

const TONES = [
	'blue', 'green', 'red', 'yellow', 'purple', 'brown',
	'orange', 'turquoise', 'gray', 'black', 'pink', 'primary', 'white',
]

/** A pleasant default multi-series sequence (theme tokens). */
export const SERIES_TONES: ThemeType[] = [
	'primary', 'purple', 'turquoise', 'orange', 'pink', 'green', 'blue', 'yellow', 'red',
]

/** Is this string one of the known theme tones (incl. -light/-tint suffixes)? */
function isTone(c: string): boolean {
	const base = c.replace(/-(light|tint|dark|\d+)$/, '')
	return TONES.includes(base)
}

/**
 * Resolve a caller color into a paintable CSS value.
 * - tone name → `var(--bgl-<tone>)`
 * - anything else (hex/rgb/var(...)) → returned as-is
 * - undefined → falls back to the series-index tone
 */
export function resolveColor(color: ThemeType | string | undefined, index = 0): string {
	if (!color) return `var(--bgl-${SERIES_TONES[index % SERIES_TONES.length]})`
	if (typeof color === 'string' && isTone(color)) return `var(--bgl-${color})`
	return color
}

/** A translucent version of a resolved color (for area fills / hovers). */
export function alpha(cssColor: string, pct: number): string {
	return `color-mix(in srgb, ${cssColor} ${pct}%, transparent)`
}

/**
 * A monochrome ramp: `count` shades of one base color, from full strength to a
 * lighter tint. Reads premium for donut/pie slices and stacked categories.
 * `index 0` is the strongest; later slices fade toward white.
 */
export function ramp(base: ThemeType | string | undefined, count: number, index = 0): string {
	const color = resolveColor(base ?? 'primary')
	if (count <= 1) return color
	// Spread mix from 100% (strongest) down to ~40% (lightest) of the base.
	const minPct = 42
	const pct = 100 - (index / (count - 1)) * (100 - minPct)
	return `color-mix(in srgb, ${color} ${pct}%, var(--bgl-box-bg))`
}