use anyhow::{bail, Result};
use bytes::Bytes;

use crate::iterators::StorageIterator;

#[derive(Clone)]
pub struct MockIterator {
    pub data: Vec<(Bytes, Bytes)>,
    pub error_when: Option<usize>,
    pub index: usize,
}

impl MockIterator {
    pub fn new(data: Vec<(Bytes, Bytes)>) -> Self {
        Self {
            data,
            index: 0,
            error_when: None,
        }
    }

    pub fn new_with_error(data: Vec<(Bytes, Bytes)>, error_when: usize) -> Self {
        Self {
            data,
            index: 0,
            error_when: Some(error_when),
        }
    }
}

impl StorageIterator for MockIterator {
    fn next(&mut self) -> Result<()> {
        if self.index < self.data.len() {
            self.index += 1;
        }
        if let Some(error_when) = self.error_when {
            if self.index == error_when {
                bail!("fake error!");
            }
        }
        Ok(())
    }

    fn key(&self) -> &[u8] {
        if let Some(error_when) = self.error_when {
            if self.index >= error_when {
                panic!("invalid access after next returns an error!");
            }
        }
        self.data[self.index].0.as_ref()
    }

    fn value(&self) -> &[u8] {
        if let Some(error_when) = self.error_when {
            if self.index >= error_when {
                panic!("invalid access after next returns an error!");
            }
        }
        self.data[self.index].1.as_ref()
    }

    fn is_valid(&self) -> bool {
        if let Some(error_when) = self.error_when {
            if self.index >= error_when {
                panic!("invalid access after next returns an error!");
            }
        }
        self.index < self.data.len()
    }
}