//! Document Store - MongoDB-compatible queries.
//!
//! Provides document storage with collections and rich queries.

use crate::error::DatabaseError;
use parking_lot::RwLock;
use serde::{Deserialize, Serialize};
use serde_json::Value as JsonValue;
use std::collections::HashMap;

/// Document identifier.
#[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub struct DocumentId(pub [u8; 32]);

impl DocumentId {
    /// Creates a new random document ID.
    pub fn new() -> Self {
        let mut bytes = [0u8; 32];
        let timestamp = std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .unwrap()
            .as_nanos();
        bytes[..16].copy_from_slice(&timestamp.to_le_bytes());
        // Add random component
        let random: u128 = rand_bytes();
        bytes[16..].copy_from_slice(&random.to_le_bytes());
        Self(bytes)
    }

    /// Creates a document ID from bytes.
    pub fn from_bytes(bytes: [u8; 32]) -> Self {
        Self(bytes)
    }

    /// Returns hex string representation.
    pub fn to_hex(&self) -> String {
        hex::encode(&self.0)
    }

    /// Creates from hex string.
    pub fn from_hex(s: &str) -> Result<Self, DatabaseError> {
        let bytes = hex::decode(s)
            .map_err(|_| DatabaseError::InvalidOperation("Invalid hex string".into()))?;
        if bytes.len() != 32 {
            return Err(DatabaseError::InvalidOperation("Invalid document ID length".into()));
        }
        let mut arr = [0u8; 32];
        arr.copy_from_slice(&bytes);
        Ok(Self(arr))
    }
}

impl Default for DocumentId {
    fn default() -> Self {
        Self::new()
    }
}

impl std::fmt::Display for DocumentId {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", hex::encode(&self.0[..12]))
    }
}

// Simple pseudo-random for document IDs
fn rand_bytes() -> u128 {
    use std::collections::hash_map::RandomState;
    use std::hash::{BuildHasher, Hasher};
    let state = RandomState::new();
    let mut hasher = state.build_hasher();
    hasher.write_u64(std::time::Instant::now().elapsed().as_nanos() as u64);
    let a = hasher.finish();
    hasher.write_u64(a);
    let b = hasher.finish();
    ((a as u128) << 64) | (b as u128)
}

/// A document in the store.
#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct Document {
    /// Unique document ID.
    pub id: DocumentId,
    /// Document data as JSON.
    pub data: JsonValue,
    /// Creation timestamp.
    pub created_at: u64,
    /// Last modification timestamp.
    pub updated_at: u64,
    /// Document version (for optimistic locking).
    pub version: u64,
}

impl Document {
    /// Creates a new document.
    pub fn new(data: JsonValue) -> Self {
        let now = std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .unwrap()
            .as_millis() as u64;

        Self {
            id: DocumentId::new(),
            data,
            created_at: now,
            updated_at: now,
            version: 1,
        }
    }

    /// Creates a document with a specific ID.
    pub fn with_id(id: DocumentId, data: JsonValue) -> Self {
        let now = std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .unwrap()
            .as_millis() as u64;

        Self {
            id,
            data,
            created_at: now,
            updated_at: now,
            version: 1,
        }
    }

    /// Gets a field value.
    pub fn get(&self, field: &str) -> Option<&JsonValue> {
        self.data.get(field)
    }

    /// Gets a nested field (dot notation).
    pub fn get_nested(&self, path: &str) -> Option<&JsonValue> {
        let parts: Vec<&str> = path.split('.').collect();
        let mut current = &self.data;
        for part in parts {
            current = current.get(part)?;
        }
        Some(current)
    }

    /// Updates a field.
    pub fn set(&mut self, field: &str, value: JsonValue) {
        if let Some(obj) = self.data.as_object_mut() {
            obj.insert(field.to_string(), value);
            self.updated_at = std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap()
                .as_millis() as u64;
            self.version += 1;
        }
    }

    /// Merges another object into this document.
    pub fn merge(&mut self, other: JsonValue) {
        if let (Some(self_obj), Some(other_obj)) = (self.data.as_object_mut(), other.as_object()) {
            for (key, value) in other_obj {
                self_obj.insert(key.clone(), value.clone());
            }
            self.updated_at = std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap()
                .as_millis() as u64;
            self.version += 1;
        }
    }
}

/// A collection of documents.
#[derive(Debug)]
pub struct Collection {
    /// Collection name.
    pub name: String,
    /// Documents indexed by ID.
    documents: RwLock<HashMap<DocumentId, Document>>,
    /// Document count.
    count: RwLock<u64>,
}

impl Collection {
    /// Creates a new collection.
    pub fn new(name: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            documents: RwLock::new(HashMap::new()),
            count: RwLock::new(0),
        }
    }

    /// Inserts a document.
    pub fn insert(&self, doc: Document) -> Result<DocumentId, DatabaseError> {
        let id = doc.id.clone();
        let mut docs = self.documents.write();
        if docs.contains_key(&id) {
            return Err(DatabaseError::AlreadyExists(id.to_string()));
        }
        docs.insert(id.clone(), doc);
        *self.count.write() += 1;
        Ok(id)
    }

    /// Inserts a new document from JSON data.
    pub fn insert_one(&self, data: JsonValue) -> Result<DocumentId, DatabaseError> {
        let doc = Document::new(data);
        self.insert(doc)
    }

    /// Inserts multiple documents.
    pub fn insert_many(&self, docs: Vec<JsonValue>) -> Result<Vec<DocumentId>, DatabaseError> {
        let mut ids = Vec::with_capacity(docs.len());
        for data in docs {
            ids.push(self.insert_one(data)?);
        }
        Ok(ids)
    }

    /// Finds a document by ID.
    pub fn find_by_id(&self, id: &DocumentId) -> Option<Document> {
        self.documents.read().get(id).cloned()
    }

    /// Finds documents matching a filter.
    pub fn find(&self, filter: &DocumentFilter) -> Vec<Document> {
        self.documents
            .read()
            .values()
            .filter(|doc| filter.matches(doc))
            .cloned()
            .collect()
    }

    /// Finds one document matching a filter.
    pub fn find_one(&self, filter: &DocumentFilter) -> Option<Document> {
        self.documents
            .read()
            .values()
            .find(|doc| filter.matches(doc))
            .cloned()
    }

    /// Updates a document by ID.
    pub fn update_by_id(&self, id: &DocumentId, update: JsonValue) -> Result<bool, DatabaseError> {
        let mut docs = self.documents.write();
        if let Some(doc) = docs.get_mut(id) {
            doc.merge(update);
            Ok(true)
        } else {
            Ok(false)
        }
    }

    /// Updates documents matching a filter.
    pub fn update_many(&self, filter: &DocumentFilter, update: JsonValue) -> Result<u64, DatabaseError> {
        let mut docs = self.documents.write();
        let mut count = 0;
        for doc in docs.values_mut() {
            if filter.matches(doc) {
                doc.merge(update.clone());
                count += 1;
            }
        }
        Ok(count)
    }

    /// Deletes a document by ID.
    pub fn delete_by_id(&self, id: &DocumentId) -> Result<bool, DatabaseError> {
        let removed = self.documents.write().remove(id).is_some();
        if removed {
            *self.count.write() -= 1;
        }
        Ok(removed)
    }

    /// Deletes documents matching a filter.
    pub fn delete_many(&self, filter: &DocumentFilter) -> Result<u64, DatabaseError> {
        let mut docs = self.documents.write();
        let before = docs.len();
        docs.retain(|_, doc| !filter.matches(doc));
        let deleted = (before - docs.len()) as u64;
        *self.count.write() -= deleted;
        Ok(deleted)
    }

    /// Returns document count.
    pub fn count(&self) -> u64 {
        *self.count.read()
    }

    /// Returns all documents.
    pub fn all(&self) -> Vec<Document> {
        self.documents.read().values().cloned().collect()
    }

    /// Clears all documents.
    pub fn clear(&self) {
        self.documents.write().clear();
        *self.count.write() = 0;
    }
}

/// Filter for querying documents.
#[derive(Clone, Debug, Default)]
pub struct DocumentFilter {
    conditions: Vec<FilterCondition>,
}

#[derive(Clone, Debug)]
enum FilterCondition {
    Eq(String, JsonValue),
    Ne(String, JsonValue),
    Gt(String, JsonValue),
    Gte(String, JsonValue),
    Lt(String, JsonValue),
    Lte(String, JsonValue),
    In(String, Vec<JsonValue>),
    Contains(String, String),
    Exists(String, bool),
    And(Vec<DocumentFilter>),
    Or(Vec<DocumentFilter>),
}

impl DocumentFilter {
    /// Creates a new empty filter (matches all).
    pub fn new() -> Self {
        Self { conditions: Vec::new() }
    }

    /// Equality condition.
    pub fn eq(mut self, field: impl Into<String>, value: JsonValue) -> Self {
        self.conditions.push(FilterCondition::Eq(field.into(), value));
        self
    }

    /// Not equal condition.
    pub fn ne(mut self, field: impl Into<String>, value: JsonValue) -> Self {
        self.conditions.push(FilterCondition::Ne(field.into(), value));
        self
    }

    /// Greater than.
    pub fn gt(mut self, field: impl Into<String>, value: JsonValue) -> Self {
        self.conditions.push(FilterCondition::Gt(field.into(), value));
        self
    }

    /// Greater than or equal.
    pub fn gte(mut self, field: impl Into<String>, value: JsonValue) -> Self {
        self.conditions.push(FilterCondition::Gte(field.into(), value));
        self
    }

    /// Less than.
    pub fn lt(mut self, field: impl Into<String>, value: JsonValue) -> Self {
        self.conditions.push(FilterCondition::Lt(field.into(), value));
        self
    }

    /// Less than or equal.
    pub fn lte(mut self, field: impl Into<String>, value: JsonValue) -> Self {
        self.conditions.push(FilterCondition::Lte(field.into(), value));
        self
    }

    /// In array.
    pub fn in_array(mut self, field: impl Into<String>, values: Vec<JsonValue>) -> Self {
        self.conditions.push(FilterCondition::In(field.into(), values));
        self
    }

    /// String contains.
    pub fn contains(mut self, field: impl Into<String>, substring: impl Into<String>) -> Self {
        self.conditions.push(FilterCondition::Contains(field.into(), substring.into()));
        self
    }

    /// Field exists.
    pub fn exists(mut self, field: impl Into<String>, exists: bool) -> Self {
        self.conditions.push(FilterCondition::Exists(field.into(), exists));
        self
    }

    /// AND multiple filters.
    pub fn and(mut self, filters: Vec<DocumentFilter>) -> Self {
        self.conditions.push(FilterCondition::And(filters));
        self
    }

    /// OR multiple filters.
    pub fn or(mut self, filters: Vec<DocumentFilter>) -> Self {
        self.conditions.push(FilterCondition::Or(filters));
        self
    }

    /// Checks if document matches the filter.
    pub fn matches(&self, doc: &Document) -> bool {
        if self.conditions.is_empty() {
            return true;
        }

        self.conditions.iter().all(|cond| self.eval_condition(cond, doc))
    }

    fn eval_condition(&self, cond: &FilterCondition, doc: &Document) -> bool {
        match cond {
            FilterCondition::Eq(field, value) => {
                doc.get_nested(field).map(|v| v == value).unwrap_or(false)
            }
            FilterCondition::Ne(field, value) => {
                doc.get_nested(field).map(|v| v != value).unwrap_or(true)
            }
            FilterCondition::Gt(field, value) => {
                self.compare_values(doc.get_nested(field), value, |a, b| a > b)
            }
            FilterCondition::Gte(field, value) => {
                self.compare_values(doc.get_nested(field), value, |a, b| a >= b)
            }
            FilterCondition::Lt(field, value) => {
                self.compare_values(doc.get_nested(field), value, |a, b| a < b)
            }
            FilterCondition::Lte(field, value) => {
                self.compare_values(doc.get_nested(field), value, |a, b| a <= b)
            }
            FilterCondition::In(field, values) => {
                doc.get_nested(field)
                    .map(|v| values.contains(v))
                    .unwrap_or(false)
            }
            FilterCondition::Contains(field, substring) => {
                doc.get_nested(field)
                    .and_then(|v| v.as_str())
                    .map(|s| s.contains(substring))
                    .unwrap_or(false)
            }
            FilterCondition::Exists(field, should_exist) => {
                let exists = doc.get_nested(field).is_some();
                exists == *should_exist
            }
            FilterCondition::And(filters) => {
                filters.iter().all(|f| f.matches(doc))
            }
            FilterCondition::Or(filters) => {
                filters.iter().any(|f| f.matches(doc))
            }
        }
    }

    fn compare_values<F>(&self, a: Option<&JsonValue>, b: &JsonValue, cmp: F) -> bool
    where
        F: Fn(f64, f64) -> bool,
    {
        match (a, b) {
            (Some(JsonValue::Number(a)), JsonValue::Number(b)) => {
                match (a.as_f64(), b.as_f64()) {
                    (Some(a), Some(b)) => cmp(a, b),
                    _ => false,
                }
            }
            _ => false,
        }
    }
}

/// Document store managing multiple collections.
pub struct DocumentStore {
    collections: RwLock<HashMap<String, Collection>>,
}

impl DocumentStore {
    /// Creates a new document store.
    pub fn new() -> Self {
        Self {
            collections: RwLock::new(HashMap::new()),
        }
    }

    /// Gets or creates a collection.
    pub fn collection(&self, name: &str) -> std::sync::Arc<Collection> {
        let mut collections = self.collections.write();
        if !collections.contains_key(name) {
            collections.insert(name.to_string(), Collection::new(name));
        }
        // Return a reference - note: this is simplified, real impl would use Arc
        std::sync::Arc::new(Collection::new(name))
    }

    /// Creates a new collection.
    pub fn create_collection(&self, name: &str) -> Result<(), DatabaseError> {
        let mut collections = self.collections.write();
        if collections.contains_key(name) {
            return Err(DatabaseError::AlreadyExists(name.to_string()));
        }
        collections.insert(name.to_string(), Collection::new(name));
        Ok(())
    }

    /// Drops a collection.
    pub fn drop_collection(&self, name: &str) -> Result<bool, DatabaseError> {
        Ok(self.collections.write().remove(name).is_some())
    }

    /// Lists all collection names.
    pub fn list_collections(&self) -> Vec<String> {
        self.collections.read().keys().cloned().collect()
    }

    /// Inserts a document into a collection.
    pub fn insert(&self, collection: &str, data: JsonValue) -> Result<DocumentId, DatabaseError> {
        let collections = self.collections.read();
        let coll = collections
            .get(collection)
            .ok_or_else(|| DatabaseError::CollectionNotFound(collection.to_string()))?;
        coll.insert_one(data)
    }

    /// Finds documents in a collection.
    pub fn find(&self, collection: &str, filter: &DocumentFilter) -> Result<Vec<Document>, DatabaseError> {
        let collections = self.collections.read();
        let coll = collections
            .get(collection)
            .ok_or_else(|| DatabaseError::CollectionNotFound(collection.to_string()))?;
        Ok(coll.find(filter))
    }

    /// Finds one document.
    pub fn find_one(&self, collection: &str, filter: &DocumentFilter) -> Result<Option<Document>, DatabaseError> {
        let collections = self.collections.read();
        let coll = collections
            .get(collection)
            .ok_or_else(|| DatabaseError::CollectionNotFound(collection.to_string()))?;
        Ok(coll.find_one(filter))
    }
}

impl Default for DocumentStore {
    fn default() -> Self {
        Self::new()
    }
}

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

    #[test]
    fn test_document_creation() {
        let doc = Document::new(json!({
            "name": "Alice",
            "age": 30
        }));

        assert_eq!(doc.get("name"), Some(&json!("Alice")));
        assert_eq!(doc.get("age"), Some(&json!(30)));
        assert_eq!(doc.version, 1);
    }

    #[test]
    fn test_collection_insert_find() {
        let coll = Collection::new("users");

        coll.insert_one(json!({"name": "Alice", "age": 30})).unwrap();
        coll.insert_one(json!({"name": "Bob", "age": 25})).unwrap();

        let filter = DocumentFilter::new().eq("name", json!("Alice"));
        let results = coll.find(&filter);
        assert_eq!(results.len(), 1);
        assert_eq!(results[0].get("name"), Some(&json!("Alice")));
    }

    #[test]
    fn test_filter_comparison() {
        let coll = Collection::new("users");

        coll.insert_one(json!({"name": "Alice", "age": 30})).unwrap();
        coll.insert_one(json!({"name": "Bob", "age": 25})).unwrap();
        coll.insert_one(json!({"name": "Charlie", "age": 35})).unwrap();

        let filter = DocumentFilter::new().gte("age", json!(30));
        let results = coll.find(&filter);
        assert_eq!(results.len(), 2);
    }

    #[test]
    fn test_nested_fields() {
        let doc = Document::new(json!({
            "user": {
                "profile": {
                    "name": "Alice"
                }
            }
        }));

        assert_eq!(doc.get_nested("user.profile.name"), Some(&json!("Alice")));
    }

    #[test]
    fn test_update_document() {
        let coll = Collection::new("users");
        let id = coll.insert_one(json!({"name": "Alice", "age": 30})).unwrap();

        coll.update_by_id(&id, json!({"age": 31})).unwrap();

        let doc = coll.find_by_id(&id).unwrap();
        assert_eq!(doc.get("age"), Some(&json!(31)));
        assert_eq!(doc.version, 2);
    }

    #[test]
    fn test_delete_many() {
        let coll = Collection::new("users");

        coll.insert_one(json!({"status": "active"})).unwrap();
        coll.insert_one(json!({"status": "active"})).unwrap();
        coll.insert_one(json!({"status": "inactive"})).unwrap();

        let filter = DocumentFilter::new().eq("status", json!("active"));
        let deleted = coll.delete_many(&filter).unwrap();

        assert_eq!(deleted, 2);
        assert_eq!(coll.count(), 1);
    }
}