import type { Connection, Signer, TransactionError } from '@solana/web3.js';
import { PublicKey, Transaction } from '@solana/web3.js';
import { TOKEN_2022_PROGRAM_ID, TOKEN_PROGRAM_ID } from '../constants.js';
import { createAmountToUiAmountInstruction } from '../instructions/amountToUiAmount.js';
import { unpackMint } from '../state/mint.js';
import { getInterestBearingMintConfigState } from '../extensions/interestBearingMint/state.js';
import { getScaledUiAmountConfig } from '../extensions/scaledUiAmount/state.js';

// Constants for interest calculations
const ONE_IN_BASIS_POINTS = 10000;
const SECONDS_PER_YEAR = 60 * 60 * 24 * 365.24;
const SYSVAR_CLOCK_PUBKEY = new PublicKey('SysvarC1ock11111111111111111111111111111111');

/**
 * Amount as a string using mint-prescribed decimals
 *
 * @param connection     Connection to use
 * @param payer          Payer of the transaction fees
 * @param mint           Mint for the account
 * @param amount         Amount of tokens to be converted to Ui Amount
 * @param programId      SPL Token program account
 *
 * @return Ui Amount generated or error
 */
export async function amountToUiAmount(
    connection: Connection,
    payer: Signer,
    mint: PublicKey,
    amount: number | bigint,
    programId = TOKEN_PROGRAM_ID,
): Promise<string | TransactionError | null> {
    const transaction = new Transaction().add(createAmountToUiAmountInstruction(mint, amount, programId));
    const { returnData, err } = (await connection.simulateTransaction(transaction, [payer], false)).value;

    if (returnData?.data) {
        return Buffer.from(returnData.data[0], returnData.data[1]).toString('utf-8');
    }
    return err;
}

/**
 * Calculates the exponent for the interest rate formula.
 * @param t1 - The start time in seconds.
 * @param t2 - The end time in seconds.
 * @param r - The interest rate in basis points.
 * @returns The calculated exponent.
 */
function calculateExponentForTimesAndRate(t1: number, t2: number, r: number): number {
    const timespan = t2 - t1;
    const numerator = r * timespan;
    const exponent = numerator / (SECONDS_PER_YEAR * ONE_IN_BASIS_POINTS);
    return Math.exp(exponent);
}

/**
 * Retrieves the current timestamp from the Solana clock sysvar.
 * @param connection - The Solana connection object.
 * @returns A promise that resolves to the current timestamp in seconds.
 * @throws An error if the sysvar clock cannot be fetched or parsed.
 */
async function getSysvarClockTimestamp(connection: Connection): Promise<number> {
    const info = await connection.getParsedAccountInfo(SYSVAR_CLOCK_PUBKEY);

    if (!info?.value) {
        throw new Error('Failed to fetch sysvar clock');
    }

    if (typeof info.value === 'object' && 'data' in info.value && 'parsed' in info.value.data) {
        return info.value.data.parsed.info.unixTimestamp;
    }

    throw new Error('Failed to parse sysvar clock');
}

/**
 * Calculates the decimal factor for a given number of decimals
 * @param decimals - Number of decimals
 * @returns The decimal factor (e.g., 100 for 2 decimals)
 */
function getDecimalFactor(decimals: number): number {
    return Math.pow(10, decimals);
}

/**
 * Convert a UI amount to an atomic amount by removing decimal scaling
 * For example, converts "1.234" with 3 decimals to 1234 (atomic units)
 *
 * @param uiAmount       UI Amount to be converted to atomic UI amount
 * @param decimals       Number of decimals for the mint
 *
 * @return Atomic UI amount
 */
function uiAmountToAtomicUiAmount(uiAmount: string, decimals: number): number {
    const uiAmountNumber = parseFloat(uiAmount);
    const decimalFactor = getDecimalFactor(decimals);
    return uiAmountNumber * decimalFactor;
}

/**
 * Convert amount to UiAmount for a mint with interest bearing extension without simulating a transaction
 * This implements the same logic as the CPI instruction available in /token/program-2022/src/extension/interest_bearing_mint/mod.rs
 *
 * Formula: A = P * e^(r * t) where
 * A = final amount after interest
 * P = principal amount (initial investment)
 * r = annual interest rate (as a decimal)
 * t = time in years
 * e = mathematical constant (~2.718)
 *
 * In this case, we are calculating the total scale factor for the interest bearing extension which is the product of two exponential functions:
 * totalScale = e^(r1 * t1) * e^(r2 * t2)
 * where r1 and r2 are the interest rates before and after the last update, and t1 and t2 are the times in years between
 * the initialization timestamp and the last update timestamp, and between the last update timestamp and the current timestamp.
 *
 * @param amount                   Amount of tokens to be converted
 * @param decimals                 Number of decimals of the mint
 * @param currentTimestamp         Current timestamp in seconds
 * @param lastUpdateTimestamp      Last time the interest rate was updated in seconds
 * @param initializationTimestamp  Time the interest bearing extension was initialized in seconds
 * @param preUpdateAverageRate     Interest rate in basis points (1 basis point = 0.01%) before last update
 * @param currentRate              Current interest rate in basis points
 *
 * @return Amount scaled by accrued interest as a string with appropriate decimal places
 */
export function amountToUiAmountForInterestBearingMintWithoutSimulation(
    amount: bigint,
    decimals: number,
    currentTimestamp: number, // in seconds
    lastUpdateTimestamp: number,
    initializationTimestamp: number,
    preUpdateAverageRate: number,
    currentRate: number,
): string {
    // Calculate pre-update exponent (interest accrued from initialization to last update)
    const preUpdateExp = calculateExponentForTimesAndRate(
        initializationTimestamp,
        lastUpdateTimestamp,
        preUpdateAverageRate,
    );

    // Calculate post-update exponent (interest accrued from last update to current time)
    const postUpdateExp = calculateExponentForTimesAndRate(lastUpdateTimestamp, currentTimestamp, currentRate);

    // Calculate total scale factor
    const totalScale = preUpdateExp * postUpdateExp;

    // Scale the amount by the total interest factor
    const scaledAmount = Number(amount) * totalScale;

    // Calculate the decimal factor (e.g. 100 for 2 decimals)
    const decimalFactor = getDecimalFactor(decimals);

    // Convert to UI amount by truncating and dividing by decimal factor
    return (Math.trunc(scaledAmount) / decimalFactor).toString();
}

/**
 * Convert amount to UiAmount for a mint with scaled UI amount extension
 * @param amount     Amount of tokens to be converted
 * @param decimals   Number of decimals of the mint
 * @param multiplier Multiplier to scale the amount
 * @return Scaled UI amount as a string
 */
export function amountToUiAmountForScaledUiAmountMintWithoutSimulation(
    amount: bigint,
    decimals: number,
    multiplier: number,
): string {
    const scaledAmount = Number(amount) * multiplier;
    const decimalFactor = getDecimalFactor(decimals);
    return (Math.trunc(scaledAmount) / decimalFactor).toString();
}

/**
 * Convert amount to UiAmount for a mint without simulating a transaction
 * This implements the same logic as `process_amount_to_ui_amount` in /token/program-2022/src/processor.rs
 * and `process_amount_to_ui_amount` in /token/program/src/processor.rs
 *
 * @param connection     Connection to use
 * @param mint           Mint to use for calculations
 * @param amount         Amount of tokens to be converted to Ui Amount
 *
 * @return Ui Amount generated
 */
export async function amountToUiAmountForMintWithoutSimulation(
    connection: Connection,
    mint: PublicKey,
    amount: bigint,
): Promise<string> {
    const accountInfo = await connection.getAccountInfo(mint);
    const programId = accountInfo?.owner;

    if (!programId?.equals(TOKEN_PROGRAM_ID) && !programId?.equals(TOKEN_2022_PROGRAM_ID)) {
        throw new Error('Invalid program ID');
    }

    const mintInfo = unpackMint(mint, accountInfo, programId);

    // Check for interest bearing mint extension
    const interestBearingMintConfigState = getInterestBearingMintConfigState(mintInfo);
    // Check for scaled UI amount extension
    const scaledUiAmountConfig = getScaledUiAmountConfig(mintInfo);

    // Standard conversion for regular mints
    if (!interestBearingMintConfigState && !scaledUiAmountConfig) {
        const decimalFactor = getDecimalFactor(mintInfo.decimals);
        return (Number(amount) / decimalFactor).toString();
    }

    // Get timestamp only if needed for special mint types
    const timestamp = await getSysvarClockTimestamp(connection);

    // Handle interest bearing mint
    if (interestBearingMintConfigState) {
        return amountToUiAmountForInterestBearingMintWithoutSimulation(
            amount,
            mintInfo.decimals,
            timestamp,
            Number(interestBearingMintConfigState.lastUpdateTimestamp),
            Number(interestBearingMintConfigState.initializationTimestamp),
            interestBearingMintConfigState.preUpdateAverageRate,
            interestBearingMintConfigState.currentRate,
        );
    }

    // At this point, we know it must be a scaled UI amount mint
    let multiplier = scaledUiAmountConfig!.multiplier;
    if (timestamp >= Number(scaledUiAmountConfig!.newMultiplierEffectiveTimestamp)) {
        multiplier = scaledUiAmountConfig!.newMultiplier;
    }
    return amountToUiAmountForScaledUiAmountMintWithoutSimulation(amount, mintInfo.decimals, multiplier);
}

/**
 * Convert an amount with interest back to the original amount without interest
 * This implements the same logic as the CPI instruction available in /token/program-2022/src/extension/interest_bearing_mint/mod.rs
 *
 * Formula: P = A / (e^(r * t)) where
 * P = principal
 * A = UI amount
 * r = annual interest rate (as a decimal)
 * t = time in years
 *
 * @param uiAmount                  UI Amount (principal plus continuously compounding interest) to be converted back to original principal
 * @param decimals                  Number of decimals for the mint
 * @param currentTimestamp          Current timestamp in seconds
 * @param lastUpdateTimestamp       Last time the interest rate was updated in seconds
 * @param initializationTimestamp   Time the interest bearing extension was initialized in seconds
 * @param preUpdateAverageRate      Interest rate in basis points (hundredths of a percent) before the last update
 * @param currentRate               Current interest rate in basis points
 *
 * @return Original amount (principal) without interest
 */
export function uiAmountToAmountForInterestBearingMintWithoutSimulation(
    uiAmount: string,
    decimals: number,
    currentTimestamp: number, // in seconds
    lastUpdateTimestamp: number,
    initializationTimestamp: number,
    preUpdateAverageRate: number,
    currentRate: number,
): bigint {
    const uiAmountScaled = uiAmountToAtomicUiAmount(uiAmount, decimals);

    // Calculate pre-update exponent
    const preUpdateExp = calculateExponentForTimesAndRate(
        initializationTimestamp,
        lastUpdateTimestamp,
        preUpdateAverageRate,
    );

    // Calculate post-update exponent
    const postUpdateExp = calculateExponentForTimesAndRate(lastUpdateTimestamp, currentTimestamp, currentRate);

    // Calculate total scale
    const totalScale = preUpdateExp * postUpdateExp;

    // Calculate original principal by dividing the UI amount (principal + interest) by the total scale
    const originalPrincipal = uiAmountScaled / totalScale;
    return BigInt(Math.trunc(originalPrincipal));
}

/**
 * Convert a UI amount back to the raw amount for a mint with a scaled UI amount extension
 * This implements the same logic as the CPI instruction available in /token/program-2022/src/extension/scaled_ui_amount/mod.rs
 *
 * @param uiAmount       UI Amount to be converted back to raw amount
 * @param decimals       Number of decimals for the mint
 * @param multiplier     Multiplier for the scaled UI amount
 *
 * @return Raw amount
 */
export function uiAmountToAmountForScaledUiAmountMintWithoutSimulation(
    uiAmount: string,
    decimals: number,
    multiplier: number,
): bigint {
    const uiAmountScaled = uiAmountToAtomicUiAmount(uiAmount, decimals);
    const rawAmount = uiAmountScaled / multiplier;
    return BigInt(Math.trunc(rawAmount));
}

/**
 * Convert a UI amount back to the raw amount
 *
 * @param connection     Connection to use
 * @param mint           Mint to use for calculations
 * @param uiAmount       UI Amount to be converted back to raw amount
 *
 * @return Raw amount
 */
export async function uiAmountToAmountForMintWithoutSimulation(
    connection: Connection,
    mint: PublicKey,
    uiAmount: string,
): Promise<bigint> {
    const accountInfo = await connection.getAccountInfo(mint);
    const programId = accountInfo?.owner;

    if (!programId?.equals(TOKEN_PROGRAM_ID) && !programId?.equals(TOKEN_2022_PROGRAM_ID)) {
        throw new Error('Invalid program ID');
    }

    const mintInfo = unpackMint(mint, accountInfo, programId);

    // Check for interest bearing mint extension
    const interestBearingMintConfigState = getInterestBearingMintConfigState(mintInfo);
    // Check for scaled UI amount extension
    const scaledUiAmountConfig = getScaledUiAmountConfig(mintInfo);

    if (!interestBearingMintConfigState && !scaledUiAmountConfig) {
        // Standard conversion for regular mints
        return BigInt(Math.trunc(uiAmountToAtomicUiAmount(uiAmount, mintInfo.decimals)));
    }

    const timestamp = await getSysvarClockTimestamp(connection);

    if (interestBearingMintConfigState) {
        return uiAmountToAmountForInterestBearingMintWithoutSimulation(
            uiAmount,
            mintInfo.decimals,
            timestamp,
            Number(interestBearingMintConfigState.lastUpdateTimestamp),
            Number(interestBearingMintConfigState.initializationTimestamp),
            interestBearingMintConfigState.preUpdateAverageRate,
            interestBearingMintConfigState.currentRate,
        );
    }

    // At this point, we know it must be a scaled UI amount mint
    let multiplier = scaledUiAmountConfig!.multiplier;
    if (timestamp >= Number(scaledUiAmountConfig!.newMultiplierEffectiveTimestamp)) {
        multiplier = scaledUiAmountConfig!.newMultiplier;
    }

    return uiAmountToAmountForScaledUiAmountMintWithoutSimulation(uiAmount, mintInfo.decimals, multiplier);
}