How Prices Get On-Chain (Pull vs Push Oracles)

use pyth_solana_receiver_sdk::price_update::{PriceUpdateV2, get_feed_id_from_hex};

#[derive(Accounts)]
pub struct Swap<'info> {
    pub user: Signer<'info>,
    pub price_update: Account<'info, PriceUpdateV2>,
    // ... other accounts
}

pub fn swap(ctx: Context<Swap>, amount_in: u64) -> Result<()> {
    let feed_id = get_feed_id_from_hex(
        "0xef0d8b6fda2ceba41da15d4095d1da392a0d2f8ed0c6c7bc0f4cfac8c280b56d", // SOL/USD
    )?;

    let price = ctx.accounts.price_update.get_price_no_older_than(
        &Clock::get()?,
        30,         // max staleness in seconds
        &feed_id,
    )?;

    // price.price is i64 (scaled); price.expo is i32 (negative exponent)
    // price.conf is u64 (95% confidence interval)
    require!(price.conf < (price.price as u64) / 200, ErrCode::WidePythConfidence);

    // Use price for swap logic...
    Ok(())
}

// Note: the price_update account is freshly written each tx by the caller's
// off-chain ingestion. Stale prices are caller-bug, not protocol bug.