/**
 * Colour sources for conditional formatting rules.
 *
 * A rule paints one CSS value (`ConditionalRule.bgColor`), and this module is
 * where that value comes from:
 *
 *   palette → `RULE_COLORS`, translucent tints over the row background
 *   status  → `--status-badge-*-fill`, the exact fills the status chips use, so
 *             "highlight the overdue rows" and the Overdue badge agree. The
 *             tokens are redefined per theme and per high-contrast mode, so the
 *             fill flips with the surface instead of stranding light ink on a
 *             light fill.
 *   custom  → the user's colour, wrapped at the palette's tint strength. Tinting
 *             rather than filling is what keeps body text above the contrast
 *             floor in both themes without pairing an ink per rule (P8).
 */

import type { StatusBadgeTone } from "./status-badge-tints"
import {
  RULE_COLORS,
  type ConditionalRule,
  type ConditionalRuleColorSource,
} from "./table-properties-types"

export const CONDITIONAL_RULE_COLOR_SOURCES: {
  value: ConditionalRuleColorSource
  label: string
}[] = [
  { value: "palette", label: "Palette" },
  { value: "status", label: "Status" },
  { value: "custom", label: "Custom" },
]

/** Status badge fills, in the DS tone order (success · info · caution · danger · neutral). */
export const STATUS_RULE_COLORS: {
  name: string
  tone: StatusBadgeTone
  bg: string
}[] = [
  { name: "Success", tone: "success", bg: "var(--status-badge-success-fill)" },
  { name: "Info", tone: "info", bg: "var(--status-badge-info-fill)" },
  { name: "Caution", tone: "warning", bg: "var(--status-badge-warning-fill)" },
  { name: "Danger", tone: "danger", bg: "var(--status-badge-danger-fill)" },
  { name: "Neutral", tone: "neutral", bg: "var(--status-badge-neutral-fill)" },
]

/** Matches the palette tokens' own strength (`--conditional-rule-*` in globals.css). */
export const CUSTOM_RULE_TINT_PERCENT = 22

export const DEFAULT_CUSTOM_RULE_COLOR = "#2f6feb"

export function customRuleBackground(color: string): string {
  return `color-mix(in oklch, ${color} ${CUSTOM_RULE_TINT_PERCENT}%, transparent)`
}

const CUSTOM_TINT_PATTERN =
  /^color-mix\(\s*in\s+oklch\s*,\s*(.+?)\s+\d+(?:\.\d+)?%\s*,\s*transparent\s*\)$/i
const PLAIN_COLOR_PATTERN = /^(#[0-9a-f]{3,8}|rgb|rgba|hsl|hsla|oklch|oklab)/i

/** The colour inside a custom tint, or `undefined` when `bg` is not one. */
export function customRuleColorFromBackground(bg: string): string | undefined {
  const match = CUSTOM_TINT_PATTERN.exec(bg.trim())
  if (!match) return undefined
  const inner = match[1].trim()
  return inner.startsWith("var(") ? undefined : inner
}

/**
 * Which picker a rule belongs to. Rules saved before colour sources existed have
 * no `colorSource`, so their background is matched against the known palettes
 * and anything else is treated as a colour the user chose.
 */
export function resolveRuleColorSource(
  rule: Pick<ConditionalRule, "bgColor" | "colorSource">,
): ConditionalRuleColorSource {
  if (rule.colorSource) return rule.colorSource
  const bg = rule.bgColor?.trim() ?? ""
  if (STATUS_RULE_COLORS.some(c => c.bg === bg)) return "status"
  if (RULE_COLORS.some(c => c.bg === bg)) return "palette"
  if (customRuleColorFromBackground(bg)) return "custom"
  if (PLAIN_COLOR_PATTERN.test(bg)) return "custom"
  return "palette"
}

/** The colour a custom rule's picker should open on. */
export function ruleCustomColor(
  rule: Pick<ConditionalRule, "bgColor" | "customColor">,
): string {
  if (rule.customColor?.trim()) return rule.customColor.trim()
  const bg = rule.bgColor?.trim() ?? ""
  return (
    customRuleColorFromBackground(bg) ??
    (PLAIN_COLOR_PATTERN.test(bg) ? bg : DEFAULT_CUSTOM_RULE_COLOR)
  )
}

/** The patch that switches a rule to `source`, keeping a sensible colour. */
export function ruleColorSourcePatch(
  rule: Pick<ConditionalRule, "bgColor" | "colorSource" | "customColor">,
  source: ConditionalRuleColorSource,
): Partial<ConditionalRule> {
  if (source === "palette") {
    const current = RULE_COLORS.find(c => c.bg === rule.bgColor)
    return { colorSource: source, bgColor: (current ?? RULE_COLORS[0]).bg }
  }
  if (source === "status") {
    const current = STATUS_RULE_COLORS.find(c => c.bg === rule.bgColor)
    return { colorSource: source, bgColor: (current ?? STATUS_RULE_COLORS[0]).bg }
  }
  const custom = ruleCustomColor(rule)
  return {
    colorSource: source,
    customColor: custom,
    bgColor: customRuleBackground(custom),
  }
}