import { StyleSheet } from "react-native";
import type { TextStyle, ViewStyle } from "react-native";

export type PickerColumn = "amPm" | "days" | "hours" | "minutes" | "seconds";

export type PerColumnValue = number | Partial<Record<PickerColumn, number>>;

export interface CustomTimerPickerStyles {
  backgroundColor?: string;
  disabledPickerContainer?: ViewStyle;
  disabledPickerItem?: TextStyle;
  durationScrollFlatList?: ViewStyle;
  durationScrollFlatListContainer?: ViewStyle;
  durationScrollFlatListContentContainer?: ViewStyle;
  /** @deprecated Use pickerLabelGap instead. Will be removed in a future version. */
  labelOffsetPercentage?: number;
  pickerAmPmContainer?: ViewStyle;
  pickerAmPmLabel?: TextStyle;
  pickerColumnWidth?: PerColumnValue;
  pickerContainer?: ViewStyle & { backgroundColor?: string };
  pickerGradientOverlay?: ViewStyle;
  pickerItem?: TextStyle;
  pickerItemContainer?: ViewStyle & { height?: number };
  pickerLabel?: TextStyle;
  pickerLabelContainer?: ViewStyle;
  pickerLabelGap?: PerColumnValue;
  selectedPickerItem?: TextStyle;
  selectedSeparateAmPmItem?: TextStyle;
  separateAmPmItem?: TextStyle;
  text?: TextStyle;
  theme?: "light" | "dark";
}

const DARK_MODE_BACKGROUND_COLOR = "#232323";
const DARK_MODE_TEXT_COLOR = "#E9E9E9";
const LIGHT_MODE_BACKGROUND_COLOR = "#F1F1F1";
const LIGHT_MODE_TEXT_COLOR = "#1B1B1B";

export const generateStyles = (customStyles: CustomTimerPickerStyles | undefined) => {
  const backgroundColor =
    customStyles?.backgroundColor ??
    (customStyles?.theme === "dark" ? DARK_MODE_BACKGROUND_COLOR : LIGHT_MODE_BACKGROUND_COLOR);

  const textColor = customStyles?.theme === "dark" ? DARK_MODE_TEXT_COLOR : LIGHT_MODE_TEXT_COLOR;

  const pickerLabelFontSize =
    customStyles?.pickerLabel?.fontSize ?? customStyles?.text?.fontSize ?? 18;
  const pickerAmPmFontSize =
    customStyles?.pickerAmPmLabel?.fontSize ??
    customStyles?.pickerLabel?.fontSize ??
    customStyles?.text?.fontSize ??
    18;
  const pickerItemFontSize =
    customStyles?.pickerItem?.fontSize ?? customStyles?.text?.fontSize ?? 25;

  // This offset makes the picker label appear to be aligned with the picker item
  // despite them having different font sizes
  const pickerLabelVerticalOffset = pickerItemFontSize - pickerLabelFontSize - 1;
  const pickerAmPmVerticalOffset = pickerItemFontSize - pickerAmPmFontSize - 1;

  // Determine whether to use the legacy percentage-based label positioning.
  // The new pixel-based system (pickerLabelGap) is the default.
  // The old system is only used when labelOffsetPercentage is explicitly set
  // without pickerLabelGap.
  const useLegacyLabelPosition =
    customStyles?.labelOffsetPercentage != null && customStyles?.pickerLabelGap == null;

  const extraLabelOffsetPercentage = customStyles?.labelOffsetPercentage ?? 8;
  const baseLeftOffsetPercentage = 70;
  const labelOffsetPercentage = baseLeftOffsetPercentage + extraLabelOffsetPercentage;

  return StyleSheet.create({
    disabledPickerContainer: {
      opacity: 0.4,
      ...customStyles?.disabledPickerContainer,
    },
    disabledPickerItem: {
      opacity: 0.2,
      ...customStyles?.disabledPickerItem,
    },
    durationScrollFlatList: {
      marginRight: "-25%",
      // These paddings allow the inner am/pm label to
      // spill out of the flatlist
      paddingRight: "25%",
      ...customStyles?.durationScrollFlatList,
    },
    durationScrollFlatListContainer: {
      flex: 1,
      ...customStyles?.durationScrollFlatListContainer,
    },
    durationScrollFlatListContentContainer: {
      ...customStyles?.durationScrollFlatListContentContainer,
    },
    maskedView: {
      flex: 1,
    },
    pickerAmPmContainer: {
      bottom: 0,
      justifyContent: "center",
      marginTop: pickerAmPmVerticalOffset,
      position: "absolute",
      top: 0,
      // Only apply percentage-based left when using legacy positioning.
      // The new pixel-based positioning is applied per-column in PickerItem.
      ...(useLegacyLabelPosition ? { left: `${labelOffsetPercentage}%` } : undefined),
      ...customStyles?.pickerLabelContainer,
      ...customStyles?.pickerAmPmContainer,
    },
    pickerAmPmLabel: {
      color: textColor,
      fontSize: 18,
      fontWeight: "bold",
      ...customStyles?.text,
      ...customStyles?.pickerLabel,
      ...customStyles?.pickerAmPmLabel,
    },
    pickerContainer: {
      backgroundColor,
      flexDirection: "row",
      width: "100%",
      ...customStyles?.pickerContainer,
    },
    pickerGradientOverlay: {
      height: "100%",
      position: "absolute",
      width: "100%",
      ...customStyles?.pickerGradientOverlay,
    },
    pickerItem: {
      color: textColor,
      fontSize: 25,
      overflow: "visible",
      textAlignVertical: "center",
      ...customStyles?.text,
      ...customStyles?.pickerItem,
    },
    pickerItemContainer: {
      alignItems: "center",
      flexDirection: "row",
      height: 50,
      justifyContent: "center",
      ...customStyles?.pickerItemContainer,
    },
    pickerLabel: {
      color: textColor,
      fontSize: 18,
      fontWeight: "bold",
      ...customStyles?.text,
      ...customStyles?.pickerLabel,
    },
    pickerLabelContainer: {
      bottom: 0,
      justifyContent: "center",
      marginTop: pickerLabelVerticalOffset,
      position: "absolute",
      top: 0,
      // Only apply percentage-based left when using legacy positioning.
      // The new pixel-based positioning is applied per-column in DurationScroll.
      ...(useLegacyLabelPosition ? { left: `${labelOffsetPercentage}%` } : undefined),
      ...customStyles?.pickerLabelContainer,
    },
    selectedPickerItem: {
      color: textColor,
      fontSize: 25,
      overflow: "visible",
      textAlignVertical: "center",
      ...customStyles?.text,
      ...customStyles?.pickerItem,
      ...customStyles?.selectedPickerItem,
    },
    selectedSeparateAmPmItem: {
      ...customStyles?.selectedSeparateAmPmItem,
    },
    separateAmPmItem: {
      ...customStyles?.separateAmPmItem,
    },
  });
};