import type { ChartConfig } from "./chart"

/** HM series colors. They resolve to existing HM palette tokens (see chart.css), never to HEX values. */
export const chartColors = [
  "var(--hm-chart-1)",
  "var(--hm-chart-2)",
  "var(--hm-chart-3)",
  "var(--hm-chart-4)",
  "var(--hm-chart-5)",
] as const

/** Light end of each HM series color (stacked bar segments): the same palette family, lighter (see chart.css). */
export const chartLightColors = [
  "var(--hm-chart-1-light)",
  "var(--hm-chart-2-light)",
  "var(--hm-chart-3-light)",
  "var(--hm-chart-4-light)",
  "var(--hm-chart-5-light)",
] as const

/** Darker tone of each HM series color, for the side walls of the solid (thick) pie and donut: the same palette family, the next step darker (see chart.css). */
export const chartSideColors = [
  "var(--hm-chart-1-side)",
  "var(--hm-chart-2-side)",
  "var(--hm-chart-3-side)",
  "var(--hm-chart-4-side)",
  "var(--hm-chart-5-side)",
] as const

/**
 * Side-wall color of a solid slice. An HM series color (default or passed explicitly) maps to its darker HM token; any other CSS
 * color is darkened where it is drawn, so no shared token changes.
 */
export function seriesSideColor(index: number, color?: string) {
  if (color === undefined) return chartSideColors[index % chartSideColors.length]
  const known = (chartColors as readonly string[]).indexOf(color)
  return known >= 0 ? chartSideColors[known] : `color-mix(in srgb, ${color} 68%, black)`
}

/** One data series. `key` becomes a CSS variable name (`--color-<key>`), so use letters, digits, `-` or `_` only. */
export type ChartSeries = {
  key: string
  label: string
  /** Any CSS color. Defaults to the HM series color for the series position. */
  color?: string
  /** Light end of a stacked bar segment (any CSS color). Defaults to the HM light color of the series position.
   * A series with a custom `color` and no `lightColor` is drawn as a flat segment. */
  lightColor?: string
}

export function seriesColor(index: number, color?: string) {
  return color ?? chartColors[index % chartColors.length]
}

export function seriesLightColor(index: number, color?: string, lightColor?: string) {
  return lightColor ?? color ?? chartLightColors[index % chartLightColors.length]
}

export function seriesToConfig(series: readonly ChartSeries[]): ChartConfig {
  return Object.fromEntries(
    series.map((item, index) => [item.key, { label: item.label, color: seriesColor(index, item.color) }]),
  )
}