use std::path::{Path, PathBuf};
use std::fs;
use anyhow::{Result, Context};
use rayon::prelude::*;
use tokenizers::Tokenizer;

/// Shard represents a single file or a part of a massive dataset.
pub struct Shard {
    pub path: PathBuf,
}

/// Zero-copy-style DataPipeline for massive unconstructed text ingestion.
pub struct DataPipeline {
    tokenizer: Tokenizer,
    shards: Vec<Shard>,
}

impl DataPipeline {
    pub fn new(vocab_path: &str) -> Result<Self> {
        let tokenizer = Tokenizer::from_file(vocab_path)
            .map_err(|e| anyhow::anyhow!("Tokenizer error: {}", e))?;
        Ok(Self {
            tokenizer,
            shards: Vec::new(),
        })
    }

    pub fn add_shard_dir(&mut self, dir: &str) -> Result<()> {
        let path = Path::new(dir);
        if path.is_dir() {
            for entry in fs::read_dir(path)? {
                let entry = entry?;
                if entry.path().is_file() {
                    self.shards.push(Shard { path: entry.path() });
                }
            }
        }
        Ok(())
    }

    /// Parses all shards in parallel and returns a stream of tokens.
    pub fn process_parallel(&self) -> Result<Vec<Vec<u32>>> {
        self.shards.par_iter().map(|shard| {
            let content = fs::read_to_string(&shard.path)
                .with_context(|| format!("Failed to read shard: {:?}", shard.path))?;
            let encoding = self.tokenizer.encode(content, true)
                .map_err(|e| anyhow::anyhow!("Encoding error: {}", e))?;
            Ok(encoding.get_ids().to_vec())
        }).collect()
    }

    /// Native Ternary Quantization: Maps token indices to ternary state vectors.
    /// In a real system, this would use a fixed random triadic projection 
    /// or a learned ternary embedding lookup.
    pub fn quantize_to_ternary(&self, tokens: &[u32], vector_dim: usize) -> Vec<Vec<i8>> {
        tokens.iter().map(|&token| {
            // Deterministic hash-based ternary projection for research validation
            let mut vec = vec![0i8; vector_dim];
            for i in 0..vector_dim {
                let hash = (token as u64).wrapping_mul(0x9e3779b9).wrapping_add(i as u64);
                let state = (hash % 3) as i8 - 1; // Maps to -1, 0, 1
                vec[i] = state;
            }
            vec
        }).collect()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_ternary_quantization() {
        // We'll mock this for now
        let tokens = vec![1, 2, 3];
        let pipeline = DataPipeline {
            tokenizer: Tokenizer::default(), // Dummy
            shards: vec![],
        };
        // This is a placeholder since Tokenizer::default() might not be what we want
        // But the logic for quantize_to_ternary is independent of the tokenizer.
        let ternary = pipeline.quantize_to_ternary(&tokens, 64);
        assert_eq!(ternary.len(), 3);
        assert_eq!(ternary[0].len(), 64);
        assert!(ternary[0].iter().all(|&x| x == -1 || x == 0 || x == 1));
    }
}
