//! Raw payload storage with optional compression and deduplication.

use flate2::Compression;
use flate2::read::GzDecoder;
use flate2::write::GzEncoder;
use rusqlite::Connection;
use sha2::{Digest, Sha256};
use std::io::{Read, Write};

use super::error::Result;
use super::time::now_ms;

/// Options for storing a payload.
pub struct StorePayloadOptions<'a> {
    pub project_id: Option<i64>,
    pub resource_type: &'a str, // 'project' | 'issue' | 'mr' | 'note' | 'discussion'
    pub gitlab_id: &'a str,     // TEXT because discussion IDs are strings
    pub json_bytes: &'a [u8],
    pub compress: bool,
}

/// Store a raw API payload with optional compression and deduplication.
/// Returns the row ID (either new or existing if duplicate).
pub fn store_payload(conn: &Connection, options: StorePayloadOptions) -> Result<i64> {
    let json_bytes = options.json_bytes;

    // 2. SHA-256 hash the JSON bytes (pre-compression)
    let mut hasher = Sha256::new();
    hasher.update(json_bytes);
    let payload_hash = format!("{:x}", hasher.finalize());

    // 3. Check for duplicate by (project_id, resource_type, gitlab_id, payload_hash)
    let existing: Option<i64> = conn
        .query_row(
            "SELECT id FROM raw_payloads
             WHERE project_id IS ? AND resource_type = ? AND gitlab_id = ? AND payload_hash = ?",
            (
                options.project_id,
                options.resource_type,
                options.gitlab_id,
                &payload_hash,
            ),
            |row| row.get(0),
        )
        .ok();

    // 4. If duplicate, return existing ID
    if let Some(id) = existing {
        return Ok(id);
    }

    // 5. Compress if requested
    let (encoding, payload_bytes): (&str, std::borrow::Cow<'_, [u8]>) = if options.compress {
        let mut encoder = GzEncoder::new(Vec::new(), Compression::default());
        encoder.write_all(json_bytes)?;
        ("gzip", std::borrow::Cow::Owned(encoder.finish()?))
    } else {
        ("identity", std::borrow::Cow::Borrowed(json_bytes))
    };

    // 6. INSERT with content_encoding
    conn.execute(
        "INSERT INTO raw_payloads
         (source, project_id, resource_type, gitlab_id, fetched_at, content_encoding, payload_hash, payload)
         VALUES ('gitlab', ?, ?, ?, ?, ?, ?, ?)",
        (
            options.project_id,
            options.resource_type,
            options.gitlab_id,
            now_ms(),
            encoding,
            &payload_hash,
            payload_bytes.as_ref(),
        ),
    )?;

    Ok(conn.last_insert_rowid())
}

/// Read a raw payload by ID, decompressing if necessary.
/// Returns None if not found.
pub fn read_payload(conn: &Connection, id: i64) -> Result<Option<serde_json::Value>> {
    let row: Option<(String, Vec<u8>)> = conn
        .query_row(
            "SELECT content_encoding, payload FROM raw_payloads WHERE id = ?",
            [id],
            |row| Ok((row.get(0)?, row.get(1)?)),
        )
        .ok();

    let Some((encoding, payload_bytes)) = row else {
        return Ok(None);
    };

    // Decompress if needed
    let json_bytes = if encoding == "gzip" {
        let mut decoder = GzDecoder::new(&payload_bytes[..]);
        let mut decompressed = Vec::new();
        decoder.read_to_end(&mut decompressed)?;
        decompressed
    } else {
        payload_bytes
    };

    let value: serde_json::Value = serde_json::from_slice(&json_bytes)?;
    Ok(Some(value))
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::core::db::create_connection;
    use tempfile::tempdir;

    fn setup_test_db() -> Connection {
        let dir = tempdir().unwrap();
        let db_path = dir.path().join("test.db");
        let conn = create_connection(&db_path).unwrap();

        // Create minimal schema for testing
        conn.execute_batch(
            "CREATE TABLE raw_payloads (
                id INTEGER PRIMARY KEY,
                source TEXT NOT NULL,
                project_id INTEGER,
                resource_type TEXT NOT NULL,
                gitlab_id TEXT NOT NULL,
                fetched_at INTEGER NOT NULL,
                content_encoding TEXT NOT NULL DEFAULT 'identity',
                payload_hash TEXT NOT NULL,
                payload BLOB NOT NULL
            );
            CREATE UNIQUE INDEX uq_raw_payloads_dedupe
                ON raw_payloads(project_id, resource_type, gitlab_id, payload_hash);",
        )
        .unwrap();

        conn
    }

    #[test]
    fn test_store_and_read_payload() {
        let conn = setup_test_db();
        let payload = serde_json::json!({"title": "Test Issue", "id": 123});
        let json_bytes = serde_json::to_vec(&payload).unwrap();

        let id = store_payload(
            &conn,
            StorePayloadOptions {
                project_id: Some(1),
                resource_type: "issue",
                gitlab_id: "123",
                json_bytes: &json_bytes,
                compress: false,
            },
        )
        .unwrap();

        let result = read_payload(&conn, id).unwrap().unwrap();
        assert_eq!(result["title"], "Test Issue");
    }

    #[test]
    fn test_compression_roundtrip() {
        let conn = setup_test_db();
        let payload = serde_json::json!({"data": "x".repeat(1000)});
        let json_bytes = serde_json::to_vec(&payload).unwrap();

        let id = store_payload(
            &conn,
            StorePayloadOptions {
                project_id: Some(1),
                resource_type: "issue",
                gitlab_id: "456",
                json_bytes: &json_bytes,
                compress: true,
            },
        )
        .unwrap();

        let result = read_payload(&conn, id).unwrap().unwrap();
        assert_eq!(result["data"], "x".repeat(1000));
    }

    #[test]
    fn test_deduplication() {
        let conn = setup_test_db();
        let payload = serde_json::json!({"id": 789});
        let json_bytes = serde_json::to_vec(&payload).unwrap();

        let id1 = store_payload(
            &conn,
            StorePayloadOptions {
                project_id: Some(1),
                resource_type: "issue",
                gitlab_id: "789",
                json_bytes: &json_bytes,
                compress: false,
            },
        )
        .unwrap();

        let id2 = store_payload(
            &conn,
            StorePayloadOptions {
                project_id: Some(1),
                resource_type: "issue",
                gitlab_id: "789",
                json_bytes: &json_bytes,
                compress: false,
            },
        )
        .unwrap();

        assert_eq!(id1, id2); // Same payload returns same ID
    }
}