pg_tviews 0.1.0-beta.12

//! Dependency type detection for `jsonb_delta` optimization
//!
//! This module analyzes TVIEW SELECT statements to determine how foreign key
//! relationships manifest in the JSONB structure. This information is used
//! to choose the appropriate `jsonb_delta` patch function for efficient updates.
//!
//! # Detection Patterns
//!
//! ## Nested Object
//! ```sql
//! jsonb_build_object('author', v_user.data)
//! ```
//! → `dependency_type = 'nested_object'`, `path = ['author']`
//!
//! ## Array Aggregation
//! ```sql
//! jsonb_build_object('comments', jsonb_agg(v_comment.data))
//! ```
//! → `dependency_type = 'array'`, `path = ['comments']`, `match_key = 'id'`
//!
//! ## Scalar (Default)
//! FK column exists but not used in JSONB composition
//! → `dependency_type = 'scalar'`, `path = NULL`

use crate::catalog::DependencyType;
use regex::Regex;
use std::sync::LazyLock;

/// Regex pattern template for nested object detection
/// Matches: '`key_name`', `v_something`.data
const NESTED_PATTERN_TEMPLATE: &str = r"'(\w+)',\s*{}.data";

/// Regex pattern template for array aggregation detection
/// Matches: '`array_name`', `jsonb_agg`(`v_something`.data ...)
/// Also handles COALESCE wrapper: COALESCE(`jsonb_agg`(...), '[]'::`jsonb`)
const ARRAY_PATTERN_TEMPLATE: &str = r"'(\w+)',\s*(?:coalesce\s*\()?\s*jsonb_agg\s*\(\s*{}.data";

/// Cached regex for inline array aggregation (no `v_entity.data` reference)
/// Matches: '`array_name`', `jsonb_agg`(`jsonb_build_object`(...))
/// Also handles COALESCE wrapper
static INLINE_ARRAY_PATTERN_REGEX: LazyLock<Regex> = LazyLock::new(|| {
    Regex::new(r"'(\w+)',\s*(?:coalesce\s*\()?\s*jsonb_agg\s*\(\s*jsonb_build_object\s*\(")
        .expect("INLINE_ARRAY_PATTERN_REGEX is valid")
});

/// Cached regex for detecting 'array_name', jsonb_agg(v_something.data ...)
static ARRAY_PATTERN_REGEX: LazyLock<Regex> = LazyLock::new(|| {
    Regex::new(r"'(\w+)',\s*(?:coalesce\s*\()?\s*jsonb_agg\s*\(\s*v_(\w+)\.data")
        .expect("ARRAY_PATTERN_REGEX is valid")
});

/// Default match key for array dependencies
const DEFAULT_ARRAY_MATCH_KEY: &str = "id";

/// Information about a detected dependency
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct DependencyInfo {
    /// Type of dependency (Scalar, `NestedObject`, Array)
    pub dep_type: DependencyType,
    /// JSONB path to the nested data (e.g., `["author"]`, `["comments"]`)
    pub jsonb_path: Option<Vec<String>>,
    /// For arrays, the key used to match elements (e.g., "id")
    pub array_match_key: Option<String>,
}

impl DependencyInfo {
    /// Create a scalar dependency (default)
    const fn scalar() -> Self {
        Self {
            dep_type: DependencyType::Scalar,
            jsonb_path: None,
            array_match_key: None,
        }
    }

    /// Create a nested object dependency
    fn nested_object(path: String) -> Self {
        Self {
            dep_type: DependencyType::NestedObject,
            jsonb_path: Some(vec![path]),
            array_match_key: None,
        }
    }

    /// Create an array dependency
    fn array(path: String, match_key: String) -> Self {
        Self {
            dep_type: DependencyType::Array,
            jsonb_path: Some(vec![path]),
            array_match_key: Some(match_key),
        }
    }
}

/// Analyze SELECT statement to detect dependency types
///
/// # Arguments
/// * `select_sql` - The SELECT statement defining the TVIEW
/// * `fk_columns` - List of FK column names from schema inference
///
/// # Returns
/// Vector of `DependencyInfo`, one per FK column (order matches input)
#[must_use]
pub fn analyze_dependencies(select_sql: &str, fk_columns: &[String]) -> Vec<DependencyInfo> {
    let mut deps = Vec::new();

    for fk_col in fk_columns {
        let dep_info = detect_dependency_type(select_sql, fk_col);
        deps.push(dep_info);
    }

    // Also detect array dependencies that might not have direct FK columns
    // This handles cases where arrays aggregate data from related tables
    let array_deps = detect_array_dependencies(select_sql);
    deps.extend(array_deps);

    deps
}

/// Infer TVIEW name from FK column name
///
/// # Conventions
/// - `fk_user` → `v_user`
/// - `fk_blog_post` → `v_blog_post`
///
/// # Returns
/// - `Some(view_name)` if FK follows convention
/// - `None` if FK doesn't start with "fk_" or is malformed
fn infer_view_name(fk_col: &str) -> Option<String> {
    if !fk_col.starts_with("fk_") {
        return None;
    }

    let entity = &fk_col[3..];
    if entity.is_empty() {
        return None;
    }

    Some(format!("v_{entity}"))
}

/// Detect how a single FK is used in the SELECT statement
fn detect_dependency_type(select_sql: &str, fk_col: &str) -> DependencyInfo {
    // Normalize SQL: remove extra whitespace, make lowercase for pattern matching
    let sql_normalized = select_sql.replace(['\n', '\t'], " ").to_lowercase();

    // Try to infer view name from FK column
    let Some(view_name) = infer_view_name(fk_col) else {
        // Can't infer view name → assume scalar
        return DependencyInfo::scalar();
    };

    // Pattern 1: Nested Object
    // Look for: 'key_name', v_something.data
    // Example: 'author', v_user.data
    let nested_pattern = NESTED_PATTERN_TEMPLATE.replace("{}", &regex::escape(&view_name));
    if let Ok(re) = Regex::new(&nested_pattern)
        && let Some(captures) = re.captures(&sql_normalized)
        && let Some(key_match) = captures.get(1)
    {
        let key_name = key_match.as_str().to_string();
        return DependencyInfo::nested_object(key_name);
    }

    // Pattern 2: Array Aggregation
    // Look for: 'array_name', jsonb_agg(v_something.data ...)
    // Example: 'comments', jsonb_agg(v_comment.data ORDER BY ...)
    // Also handles COALESCE wrapper
    let array_pattern = ARRAY_PATTERN_TEMPLATE.replace("{}", &regex::escape(&view_name));
    if let Ok(re) = Regex::new(&array_pattern)
        && let Some(captures) = re.captures(&sql_normalized)
        && let Some(key_match) = captures.get(1)
    {
        let array_name = key_match.as_str().to_string();
        // Convention: arrays use "id" as match key
        return DependencyInfo::array(array_name, DEFAULT_ARRAY_MATCH_KEY.to_string());
    }

    // Default: Scalar (FK exists but not used in JSONB composition)
    DependencyInfo::scalar()
}

/// Detect array dependencies from `jsonb_agg` patterns in SELECT statement
/// This finds arrays that aggregate data from other TVIEWs, even if no direct FK exists
fn detect_array_dependencies(select_sql: &str) -> Vec<DependencyInfo> {
    let mut deps = Vec::new();
    let mut seen_keys = std::collections::HashSet::new();

    // Normalize SQL for pattern matching
    let sql_normalized = select_sql.replace(['\n', '\t'], " ").to_lowercase();

    // Pattern 1: 'array_name', jsonb_agg(v_something.data ...) — uses cached regex
    for capture in ARRAY_PATTERN_REGEX.captures_iter(&sql_normalized) {
        if let Some(array_name) = capture.get(1) {
            let key = array_name.as_str().to_string();
            if seen_keys.insert(key.clone()) {
                deps.push(DependencyInfo::array(
                    key,
                    DEFAULT_ARRAY_MATCH_KEY.to_string(),
                ));
            }
        }
    }

    // Pattern 2: 'array_name', jsonb_agg(jsonb_build_object(...)) — uses cached regex
    for capture in INLINE_ARRAY_PATTERN_REGEX.captures_iter(&sql_normalized) {
        if let Some(array_name) = capture.get(1) {
            let key = array_name.as_str().to_string();
            if seen_keys.insert(key.clone()) {
                deps.push(DependencyInfo::array(
                    key,
                    DEFAULT_ARRAY_MATCH_KEY.to_string(),
                ));
            }
        }
    }

    deps
}

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

    #[test]
    fn test_detect_nested_object_simple() {
        let sql = r"
            SELECT pk_post, fk_user,
                   jsonb_build_object('id', id, 'author', v_user.data) AS data
            FROM tb_post
            LEFT JOIN v_user ON v_user.pk_user = fk_user
        ";
        let fk_cols = vec!["fk_user".to_string()];

        let deps = analyze_dependencies(sql, &fk_cols);

        assert_eq!(deps.len(), 1, "Should detect 1 dependency");
        assert_eq!(deps[0].dep_type, DependencyType::NestedObject);
        assert_eq!(deps[0].jsonb_path, Some(vec!["author".to_string()]));
        assert_eq!(deps[0].array_match_key, None);
    }

    #[test]
    fn test_detect_array_simple() {
        let sql = r"
            SELECT pk_user,
                   jsonb_build_object(
                       'id', id,
                       'posts', jsonb_agg(v_post.data ORDER BY created_at)
                   ) AS data
            FROM tb_user
            LEFT JOIN v_post ON v_post.fk_user = pk_user
            GROUP BY pk_user, id
        ";
        let fk_cols = vec!["fk_post".to_string()]; // Inferred from v_post reference

        let deps = analyze_dependencies(sql, &fk_cols);

        assert_eq!(deps.len(), 1);
        assert_eq!(deps[0].dep_type, DependencyType::Array);
        assert_eq!(deps[0].jsonb_path, Some(vec!["posts".to_string()]));
        assert_eq!(deps[0].array_match_key, Some("id".to_string())); // Convention
    }

    #[test]
    fn test_detect_scalar_direct_column() {
        let sql = r"
            SELECT pk_post, jsonb_build_object('id', id, 'title', title) AS data
            FROM tb_post
        ";
        let fk_cols = vec![]; // No FKs

        let deps = analyze_dependencies(sql, &fk_cols);

        assert_eq!(deps.len(), 0, "No dependencies for scalar-only TVIEW");
    }

    #[test]
    fn test_detect_multiple_dependencies() {
        let sql = r"
            SELECT pk_post, fk_user, fk_category,
                   jsonb_build_object(
                       'id', id,
                       'title', title,
                       'author', v_user.data,
                       'category', v_category.data,
                       'comments', jsonb_agg(v_comment.data)
                   ) AS data
            FROM tb_post
            LEFT JOIN v_user ON v_user.pk_user = fk_user
            LEFT JOIN v_category ON v_category.pk_category = fk_category
            LEFT JOIN v_comment ON v_comment.fk_post = pk_post
            GROUP BY pk_post, fk_user, fk_category, v_user.data, v_category.data
        ";
        let fk_cols = vec![
            "fk_user".to_string(),
            "fk_category".to_string(),
            "fk_comment".to_string(),
        ];

        let deps = analyze_dependencies(sql, &fk_cols);

        assert_eq!(deps.len(), 3);

        // fk_user → nested object
        assert_eq!(deps[0].dep_type, DependencyType::NestedObject);
        assert_eq!(deps[0].jsonb_path, Some(vec!["author".to_string()]));

        // fk_category → nested object
        assert_eq!(deps[1].dep_type, DependencyType::NestedObject);
        assert_eq!(deps[1].jsonb_path, Some(vec!["category".to_string()]));

        // fk_comment → array
        assert_eq!(deps[2].dep_type, DependencyType::Array);
        assert_eq!(deps[2].jsonb_path, Some(vec!["comments".to_string()]));
        assert_eq!(deps[2].array_match_key, Some("id".to_string()));
    }

    #[test]
    fn test_detect_inline_jsonb_agg() {
        let sql = "SELECT pk_post, jsonb_build_object(
            'title', p.title,
            'comments', COALESCE(jsonb_agg(
                jsonb_build_object('id', c.pk_comment, 'text', c.text)
                ORDER BY c.pk_comment
            ) FILTER (WHERE c.pk_comment IS NOT NULL), '[]'::jsonb)
        ) AS data FROM tb_post p LEFT JOIN tb_comment c ON c.fk_post = p.pk_post";
        let fk_cols = vec!["fk_user".to_string()];

        let deps = analyze_dependencies(sql, &fk_cols);

        // fk_user is scalar (no v_user.data reference) + 1 inline array dep
        assert!(
            deps.iter().any(|d| d.dep_type == DependencyType::Array
                && d.jsonb_path == Some(vec!["comments".to_string()])),
            "Should detect inline jsonb_agg array dependency for 'comments'"
        );
    }

    #[test]
    fn test_detect_no_fk_in_select() {
        // FK exists in schema but isn't referenced in SELECT
        let sql = r"
            SELECT pk_post, jsonb_build_object('id', id) AS data
            FROM tb_post
        ";
        let fk_cols = vec!["fk_user".to_string()];

        let deps = analyze_dependencies(sql, &fk_cols);

        // Should still return 1 dependency, but type = Scalar (not used)
        assert_eq!(deps.len(), 1);
        assert_eq!(deps[0].dep_type, DependencyType::Scalar);
        assert_eq!(deps[0].jsonb_path, None);
    }
}