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use anyhow::bail;
use std::fmt::Debug;
use crate::result::SQLiteError;

/// # Magic Header String (16 Bytes)
///  Every valid SQLite database file begins with the following
/// 16 bytes (in hex): `53 51 4c 69 74 65 20 66 6f 72 6d 61 74 20 33 00`.
/// This byte sequence corresponds to the UTF-8 string `SQLite format 3`
/// including the nul terminator character at the end.
pub struct MagicHeaderString<'a>(&'a [u8]);
impl<'a> TryFrom<&'a [u8]> for MagicHeaderString<'a> {
    type Error = SQLiteError;

    fn try_from(payload: &'a [u8]) -> Result<Self, Self::Error> {
        const VALID_SIZE: usize = 16;
        const SIGNATURE: [u8; VALID_SIZE] = [
            0x53, 0x51, 0x4c, 0x69, 0x74, 0x65, 0x20, 0x66, 0x6f, 0x72, 0x6d, 0x61, 0x74, 0x20,
            0x33, 0x00,
        ];
        if payload.len() != VALID_SIZE {
            bail!("Invalid size for MagicHeaderString");
        }

        for (idx, byte) in SIGNATURE.iter().enumerate() {
            if payload.get(idx) != Some(byte) {
                bail!("Invalid payload for MagicHeaderString");
            }
        }

        Ok(Self(payload))
    }
}

impl<'a> Debug for MagicHeaderString<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let output = format!("{:02x?}", self.0);
        f.debug_tuple("MagicHeaderString").field(&output).finish()
    }
}