use shared::types::{
    DatasetId, DatasetManifest, ObjectRef, SchemaFingerprint,
    ColumnMeta, Lineage, FreshnessContract, Sensitivity,
};
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::RwLock;

use storaged::ops;
use object_store::ObjectStore;

/// Partial metadata update — only set fields are applied.
#[derive(Debug, Clone, Default, serde::Deserialize)]
pub struct MetadataUpdate {
    pub description: Option<String>,
    pub owner: Option<String>,
    pub sensitivity: Option<Sensitivity>,
    pub tags: Option<Vec<String>>,
    pub columns: Option<Vec<ColumnMeta>>,
    pub lineage: Option<Lineage>,
    pub freshness: Option<FreshnessContract>,
    pub row_count: Option<u64>,
}

const MANIFEST_PREFIX: &str = "_catalog/manifests";

/// In-memory dataset registry backed by manifest persistence in object storage.
#[derive(Clone)]
pub struct Registry {
    datasets: Arc<RwLock<HashMap<DatasetId, DatasetManifest>>>,
    store: Arc<dyn ObjectStore>,
}

impl Registry {
    pub fn new(store: Arc<dyn ObjectStore>) -> Self {
        Self {
            datasets: Arc::new(RwLock::new(HashMap::new())),
            store,
        }
    }

    /// Rebuild in-memory index from persisted manifests on startup.
    pub async fn rebuild(&self) -> Result<usize, String> {
        let keys = ops::list(&self.store, Some(MANIFEST_PREFIX)).await?;
        let mut datasets = self.datasets.write().await;
        datasets.clear();
        for key in &keys {
            let data = ops::get(&self.store, key).await?;
            let manifest: DatasetManifest =
                serde_json::from_slice(&data).map_err(|e| e.to_string())?;
            datasets.insert(manifest.id.clone(), manifest);
        }
        let count = datasets.len();
        tracing::info!("catalog rebuilt: {count} datasets loaded");
        Ok(count)
    }

    /// Register a new dataset. Persists manifest to storage before updating memory.
    pub async fn register(
        &self,
        name: String,
        schema_fingerprint: SchemaFingerprint,
        objects: Vec<ObjectRef>,
    ) -> Result<DatasetManifest, String> {
        let now = chrono::Utc::now();
        let manifest = DatasetManifest {
            id: DatasetId::new(),
            name,
            schema_fingerprint,
            objects,
            created_at: now,
            updated_at: now,
            description: String::new(),
            owner: String::new(),
            sensitivity: None,
            columns: vec![],
            lineage: None,
            freshness: None,
            tags: vec![],
            row_count: None,
        };

        // Write-ahead: persist before in-memory update
        let manifest_key = format!("{MANIFEST_PREFIX}/{}.json", manifest.id);
        let json = serde_json::to_vec_pretty(&manifest).map_err(|e| e.to_string())?;
        ops::put(&self.store, &manifest_key, json.into()).await?;

        let mut datasets = self.datasets.write().await;
        datasets.insert(manifest.id.clone(), manifest.clone());

        tracing::info!("registered dataset: {} ({})", manifest.name, manifest.id);
        Ok(manifest)
    }

    /// Update metadata on an existing dataset (owner, description, tags, sensitivity, etc.)
    pub async fn update_metadata(
        &self,
        name: &str,
        updates: MetadataUpdate,
    ) -> Result<DatasetManifest, String> {
        let mut datasets = self.datasets.write().await;
        let manifest = datasets.values_mut()
            .find(|d| d.name == name)
            .ok_or_else(|| format!("dataset not found: {name}"))?;

        if let Some(desc) = updates.description { manifest.description = desc; }
        if let Some(owner) = updates.owner { manifest.owner = owner; }
        if let Some(sens) = updates.sensitivity { manifest.sensitivity = Some(sens); }
        if let Some(tags) = updates.tags { manifest.tags = tags; }
        if let Some(cols) = updates.columns { manifest.columns = cols; }
        if let Some(lineage) = updates.lineage { manifest.lineage = Some(lineage); }
        if let Some(freshness) = updates.freshness { manifest.freshness = Some(freshness); }
        if let Some(count) = updates.row_count { manifest.row_count = Some(count); }
        manifest.updated_at = chrono::Utc::now();

        // Persist
        let manifest_key = format!("{MANIFEST_PREFIX}/{}.json", manifest.id);
        let json = serde_json::to_vec_pretty(manifest).map_err(|e| e.to_string())?;
        ops::put(&self.store, &manifest_key, json.into()).await?;

        let result = manifest.clone();
        Ok(result)
    }

    /// Get a dataset by ID.
    pub async fn get(&self, id: &DatasetId) -> Option<DatasetManifest> {
        let datasets = self.datasets.read().await;
        datasets.get(id).cloned()
    }

    /// Get a dataset by name.
    pub async fn get_by_name(&self, name: &str) -> Option<DatasetManifest> {
        let datasets = self.datasets.read().await;
        datasets.values().find(|d| d.name == name).cloned()
    }

    /// List all datasets.
    pub async fn list(&self) -> Vec<DatasetManifest> {
        let datasets = self.datasets.read().await;
        datasets.values().cloned().collect()
    }

    /// Re-read the parquet footer(s) for a dataset and repopulate `row_count`
    /// and `columns` from reality. Use this to repair manifests whose
    /// metadata was lost (e.g. migrated from a pre-Phase 10 catalog).
    ///
    /// Does NOT touch owner/description/sensitivity/lineage/tags — only
    /// the structural facts that parquet can tell us authoritatively.
    /// The existing `schema_fingerprint` is updated if the recomputed one
    /// differs; a warning is logged so drift is visible.
    pub async fn resync_from_parquet(&self, name: &str) -> Result<DatasetManifest, String> {
        use shared::arrow_helpers::{fingerprint_schema, parquet_to_record_batches};

        // Snapshot the target manifest so we don't hold the write lock during IO.
        let (id, objects, old_fp) = {
            let datasets = self.datasets.read().await;
            let m = datasets
                .values()
                .find(|d| d.name == name)
                .ok_or_else(|| format!("dataset not found: {name}"))?;
            (m.id.clone(), m.objects.clone(), m.schema_fingerprint.clone())
        };

        if objects.is_empty() {
            return Err(format!("dataset '{name}' has no object references to resync from"));
        }

        let mut total_rows: u64 = 0;
        let mut first_schema: Option<arrow::datatypes::SchemaRef> = None;
        for obj in &objects {
            let data = ops::get(&self.store, &obj.key).await
                .map_err(|e| format!("read {}: {e}", obj.key))?;
            let (schema, batches) = parquet_to_record_batches(&data)
                .map_err(|e| format!("parse {}: {e}", obj.key))?;
            let rows: u64 = batches.iter().map(|b| b.num_rows() as u64).sum();
            total_rows += rows;
            if first_schema.is_none() {
                first_schema = Some(schema);
            }
        }

        let schema = first_schema.ok_or("no schema recovered")?;
        let new_fp = fingerprint_schema(&schema);
        if new_fp != old_fp {
            tracing::warn!(
                "dataset '{}' schema fingerprint drift: {} -> {} (updating to match parquet reality)",
                name, old_fp.0, new_fp.0,
            );
        }

        let columns: Vec<ColumnMeta> = schema
            .fields()
            .iter()
            .map(|f| ColumnMeta {
                name: f.name().clone(),
                data_type: f.data_type().to_string(),
                sensitivity: None,
                description: String::new(),
                is_pii: false,
            })
            .collect();

        // Apply updates.
        let mut datasets = self.datasets.write().await;
        let manifest = datasets
            .get_mut(&id)
            .ok_or_else(|| format!("dataset disappeared during resync: {name}"))?;
        manifest.row_count = Some(total_rows);
        manifest.columns = columns;
        manifest.schema_fingerprint = new_fp;
        manifest.updated_at = chrono::Utc::now();

        // Persist.
        let manifest_key = format!("{MANIFEST_PREFIX}/{}.json", manifest.id);
        let json = serde_json::to_vec_pretty(manifest).map_err(|e| e.to_string())?;
        ops::put(&self.store, &manifest_key, json.into()).await?;

        tracing::info!("resynced '{name}': row_count={total_rows}, {} columns", manifest.columns.len());
        Ok(manifest.clone())
    }

    /// Resync every dataset that currently has a null row_count.
    /// Returns (successes, failures) where each entry is (name, detail).
    pub async fn resync_missing(&self) -> (Vec<(String, u64)>, Vec<(String, String)>) {
        let names: Vec<String> = {
            let datasets = self.datasets.read().await;
            datasets
                .values()
                .filter(|d| d.row_count.is_none() || d.columns.is_empty())
                .map(|d| d.name.clone())
                .collect()
        };

        let mut ok = Vec::new();
        let mut err = Vec::new();
        for name in names {
            match self.resync_from_parquet(&name).await {
                Ok(m) => ok.push((name, m.row_count.unwrap_or(0))),
                Err(e) => err.push((name, e)),
            }
        }
        (ok, err)
    }

    /// Add objects to an existing dataset.
    pub async fn add_objects(
        &self,
        id: &DatasetId,
        new_objects: Vec<ObjectRef>,
    ) -> Result<DatasetManifest, String> {
        let mut datasets = self.datasets.write().await;
        let manifest = datasets.get_mut(id).ok_or_else(|| format!("dataset not found: {id}"))?;

        manifest.objects.extend(new_objects);
        manifest.updated_at = chrono::Utc::now();

        // Persist updated manifest
        let manifest_key = format!("{MANIFEST_PREFIX}/{}.json", manifest.id);
        let json = serde_json::to_vec_pretty(manifest).map_err(|e| e.to_string())?;
        ops::put(&self.store, &manifest_key, json.into()).await?;

        Ok(manifest.clone())
    }
}