-- ============================================================================
-- SHARED RLS POLICIES - ERP-Suite Core Library
-- ============================================================================
-- Purpose: Centralized Row-Level Security policies for multi-tenant isolation
-- Location: apps/shared-libs/core/database/policies/rls-policies.sql
-- Usage: Applied dynamically via apply-rls.ts functions
-- ============================================================================

-- ============================================================================
-- HELPER FUNCTIONS FOR RLS
-- ============================================================================

-- Function: Get current tenant ID from session context
CREATE OR REPLACE FUNCTION get_current_tenant_id()
RETURNS UUID AS $$
BEGIN
    RETURN NULLIF(current_setting('app.current_tenant_id', true), '')::UUID;
EXCEPTION
    WHEN OTHERS THEN
        RETURN NULL;
END;
$$ LANGUAGE plpgsql STABLE SECURITY DEFINER;

COMMENT ON FUNCTION get_current_tenant_id() IS
'Retrieves the tenant_id from the current session context for RLS policies.
Returns NULL if not set. Used by all tenant isolation policies.';

-- Function: Get current user ID from session context
CREATE OR REPLACE FUNCTION get_current_user_id()
RETURNS UUID AS $$
BEGIN
    RETURN NULLIF(current_setting('app.current_user_id', true), '')::UUID;
EXCEPTION
    WHEN OTHERS THEN
        RETURN NULL;
END;
$$ LANGUAGE plpgsql STABLE SECURITY DEFINER;

COMMENT ON FUNCTION get_current_user_id() IS
'Retrieves the user_id from the current session context.
Used for user-specific RLS policies (read/write own data).';

-- Function: Get current user role from session context
CREATE OR REPLACE FUNCTION get_current_user_role()
RETURNS TEXT AS $$
BEGIN
    RETURN current_setting('app.current_user_role', true);
EXCEPTION
    WHEN OTHERS THEN
        RETURN 'guest';
END;
$$ LANGUAGE plpgsql STABLE SECURITY DEFINER;

COMMENT ON FUNCTION get_current_user_role() IS
'Retrieves the user role from the current session context.
Used for role-based access control in RLS policies. Defaults to "guest".';

-- Function: Check if current user is admin
CREATE OR REPLACE FUNCTION is_current_user_admin()
RETURNS BOOLEAN AS $$
BEGIN
    RETURN get_current_user_role() IN ('admin', 'super_admin', 'system_admin');
END;
$$ LANGUAGE plpgsql STABLE SECURITY DEFINER;

COMMENT ON FUNCTION is_current_user_admin() IS
'Returns TRUE if the current user has an admin role.
Used for admin bypass policies.';

-- ============================================================================
-- GENERIC RLS POLICY TEMPLATES
-- ============================================================================

-- POLICY 1: TENANT_ISOLATION_POLICY
-- Purpose: Ensures users can only access data from their own tenant
-- Usage: Apply to all tables with tenant_id column
-- ============================================================================

/*
TEMPLATE FOR TENANT_ISOLATION_POLICY:

ALTER TABLE {schema}.{table} ENABLE ROW LEVEL SECURITY;

CREATE POLICY tenant_isolation_{table}
ON {schema}.{table}
FOR ALL
TO authenticated
USING (tenant_id = get_current_tenant_id())
WITH CHECK (tenant_id = get_current_tenant_id());

COMMENT ON POLICY tenant_isolation_{table} ON {schema}.{table} IS
'Multi-tenant isolation: Users can only access records from their own tenant.
Applied to all operations (SELECT, INSERT, UPDATE, DELETE).';
*/

-- ============================================================================
-- POLICY 2: USER_DATA_POLICY
-- Purpose: Restricts access to data created by or assigned to the current user
-- Usage: Apply to tables with created_by or assigned_to columns
-- ============================================================================

/*
TEMPLATE FOR USER_DATA_POLICY:

ALTER TABLE {schema}.{table} ENABLE ROW LEVEL SECURITY;

CREATE POLICY user_data_{table}
ON {schema}.{table}
FOR ALL
TO authenticated
USING (
    tenant_id = get_current_tenant_id()
    AND (
        created_by = get_current_user_id()
        OR assigned_to = get_current_user_id()
        OR owner_id = get_current_user_id()
    )
)
WITH CHECK (
    tenant_id = get_current_tenant_id()
    AND (
        created_by = get_current_user_id()
        OR assigned_to = get_current_user_id()
        OR owner_id = get_current_user_id()
    )
);

COMMENT ON POLICY user_data_{table} ON {schema}.{table} IS
'User-level isolation: Users can only access their own records.
Checks: created_by, assigned_to, or owner_id matches current user.';
*/

-- ============================================================================
-- POLICY 3: READ_OWN_DATA_POLICY
-- Purpose: Allows users to read only their own data (more permissive for SELECT)
-- Usage: Apply when users need read access to own data but restricted write
-- ============================================================================

/*
TEMPLATE FOR READ_OWN_DATA_POLICY:

ALTER TABLE {schema}.{table} ENABLE ROW LEVEL SECURITY;

CREATE POLICY read_own_data_{table}
ON {schema}.{table}
FOR SELECT
TO authenticated
USING (
    tenant_id = get_current_tenant_id()
    AND (
        created_by = get_current_user_id()
        OR assigned_to = get_current_user_id()
        OR owner_id = get_current_user_id()
    )
);

COMMENT ON POLICY read_own_data_{table} ON {schema}.{table} IS
'Read access: Users can view records they created, are assigned to, or own.
SELECT only - write operations controlled by separate policies.';
*/

-- ============================================================================
-- POLICY 4: WRITE_OWN_DATA_POLICY
-- Purpose: Allows users to insert/update/delete only their own data
-- Usage: Companion to READ_OWN_DATA_POLICY for write operations
-- ============================================================================

/*
TEMPLATE FOR WRITE_OWN_DATA_POLICY:

ALTER TABLE {schema}.{table} ENABLE ROW LEVEL SECURITY;

-- INSERT policy
CREATE POLICY write_own_data_insert_{table}
ON {schema}.{table}
FOR INSERT
TO authenticated
WITH CHECK (
    tenant_id = get_current_tenant_id()
    AND created_by = get_current_user_id()
);

-- UPDATE policy
CREATE POLICY write_own_data_update_{table}
ON {schema}.{table}
FOR UPDATE
TO authenticated
USING (
    tenant_id = get_current_tenant_id()
    AND (
        created_by = get_current_user_id()
        OR owner_id = get_current_user_id()
    )
)
WITH CHECK (
    tenant_id = get_current_tenant_id()
    AND (
        created_by = get_current_user_id()
        OR owner_id = get_current_user_id()
    )
);

-- DELETE policy
CREATE POLICY write_own_data_delete_{table}
ON {schema}.{table}
FOR DELETE
TO authenticated
USING (
    tenant_id = get_current_tenant_id()
    AND (
        created_by = get_current_user_id()
        OR owner_id = get_current_user_id()
    )
);

COMMENT ON POLICY write_own_data_insert_{table} ON {schema}.{table} IS
'Write access (INSERT): Users can only create records for themselves.';

COMMENT ON POLICY write_own_data_update_{table} ON {schema}.{table} IS
'Write access (UPDATE): Users can only update their own records.';

COMMENT ON POLICY write_own_data_delete_{table} ON {schema}.{table} IS
'Write access (DELETE): Users can only delete their own records.';
*/

-- ============================================================================
-- POLICY 5: ADMIN_BYPASS_POLICY
-- Purpose: Allows admin users to bypass RLS restrictions for support/management
-- Usage: Apply as permissive policy to allow admin full access
-- ============================================================================

/*
TEMPLATE FOR ADMIN_BYPASS_POLICY:

ALTER TABLE {schema}.{table} ENABLE ROW LEVEL SECURITY;

CREATE POLICY admin_bypass_{table}
ON {schema}.{table}
FOR ALL
TO authenticated
USING (is_current_user_admin())
WITH CHECK (is_current_user_admin());

COMMENT ON POLICY admin_bypass_{table} ON {schema}.{table} IS
'Admin bypass: Admin users (admin, super_admin, system_admin) have full access.
Use for support, troubleshooting, and system management.
Security: Only assign admin roles to trusted users.';
*/

-- ============================================================================
-- UTILITY FUNCTION: Apply RLS Policies Dynamically
-- ============================================================================

-- Function: Apply tenant isolation policy to a table
CREATE OR REPLACE FUNCTION apply_tenant_isolation_policy(
    p_schema TEXT,
    p_table TEXT,
    p_tenant_column TEXT DEFAULT 'tenant_id'
)
RETURNS VOID AS $$
DECLARE
    v_policy_name TEXT;
BEGIN
    v_policy_name := 'tenant_isolation_' || p_table;

    -- Enable RLS
    EXECUTE format('ALTER TABLE %I.%I ENABLE ROW LEVEL SECURITY', p_schema, p_table);

    -- Drop policy if exists
    EXECUTE format(
        'DROP POLICY IF EXISTS %I ON %I.%I',
        v_policy_name, p_schema, p_table
    );

    -- Create policy
    EXECUTE format(
        'CREATE POLICY %I ON %I.%I FOR ALL TO authenticated USING (%I = get_current_tenant_id()) WITH CHECK (%I = get_current_tenant_id())',
        v_policy_name, p_schema, p_table, p_tenant_column, p_tenant_column
    );

    -- Add comment
    EXECUTE format(
        'COMMENT ON POLICY %I ON %I.%I IS %L',
        v_policy_name, p_schema, p_table,
        'Multi-tenant isolation: Users can only access records from their own tenant.'
    );

    RAISE NOTICE 'Applied tenant_isolation_policy to %.%', p_schema, p_table;
END;
$$ LANGUAGE plpgsql;

COMMENT ON FUNCTION apply_tenant_isolation_policy IS
'Applies tenant isolation RLS policy to a table.
Parameters:
  - p_schema: Schema name
  - p_table: Table name
  - p_tenant_column: Column name for tenant isolation (default: tenant_id)';

-- Function: Apply admin bypass policy to a table
CREATE OR REPLACE FUNCTION apply_admin_bypass_policy(
    p_schema TEXT,
    p_table TEXT
)
RETURNS VOID AS $$
DECLARE
    v_policy_name TEXT;
BEGIN
    v_policy_name := 'admin_bypass_' || p_table;

    -- Enable RLS (if not already enabled)
    EXECUTE format('ALTER TABLE %I.%I ENABLE ROW LEVEL SECURITY', p_schema, p_table);

    -- Drop policy if exists
    EXECUTE format(
        'DROP POLICY IF EXISTS %I ON %I.%I',
        v_policy_name, p_schema, p_table
    );

    -- Create policy
    EXECUTE format(
        'CREATE POLICY %I ON %I.%I FOR ALL TO authenticated USING (is_current_user_admin()) WITH CHECK (is_current_user_admin())',
        v_policy_name, p_schema, p_table
    );

    -- Add comment
    EXECUTE format(
        'COMMENT ON POLICY %I ON %I.%I IS %L',
        v_policy_name, p_schema, p_table,
        'Admin bypass: Admin users have full access for support and management.'
    );

    RAISE NOTICE 'Applied admin_bypass_policy to %.%', p_schema, p_table;
END;
$$ LANGUAGE plpgsql;

COMMENT ON FUNCTION apply_admin_bypass_policy IS
'Applies admin bypass RLS policy to a table.
Admins can access all records regardless of tenant or ownership.
Parameters:
  - p_schema: Schema name
  - p_table: Table name';

-- Function: Apply user data policy to a table
CREATE OR REPLACE FUNCTION apply_user_data_policy(
    p_schema TEXT,
    p_table TEXT,
    p_user_columns TEXT[] DEFAULT ARRAY['created_by', 'assigned_to', 'owner_id']::TEXT[]
)
RETURNS VOID AS $$
DECLARE
    v_policy_name TEXT;
    v_using_clause TEXT;
    v_column TEXT;
    v_conditions TEXT[] := ARRAY[]::TEXT[];
BEGIN
    v_policy_name := 'user_data_' || p_table;

    -- Build USING clause with provided user columns
    FOREACH v_column IN ARRAY p_user_columns
    LOOP
        v_conditions := array_append(v_conditions, format('%I = get_current_user_id()', v_column));
    END LOOP;

    v_using_clause := 'tenant_id = get_current_tenant_id() AND (' || array_to_string(v_conditions, ' OR ') || ')';

    -- Enable RLS
    EXECUTE format('ALTER TABLE %I.%I ENABLE ROW LEVEL SECURITY', p_schema, p_table);

    -- Drop policy if exists
    EXECUTE format(
        'DROP POLICY IF EXISTS %I ON %I.%I',
        v_policy_name, p_schema, p_table
    );

    -- Create policy
    EXECUTE format(
        'CREATE POLICY %I ON %I.%I FOR ALL TO authenticated USING (%s) WITH CHECK (%s)',
        v_policy_name, p_schema, p_table, v_using_clause, v_using_clause
    );

    -- Add comment
    EXECUTE format(
        'COMMENT ON POLICY %I ON %I.%I IS %L',
        v_policy_name, p_schema, p_table,
        'User-level isolation: Users can only access their own records based on: ' || array_to_string(p_user_columns, ', ')
    );

    RAISE NOTICE 'Applied user_data_policy to %.% using columns: %', p_schema, p_table, array_to_string(p_user_columns, ', ');
END;
$$ LANGUAGE plpgsql;

COMMENT ON FUNCTION apply_user_data_policy IS
'Applies user data RLS policy to a table.
Users can only access records they created, are assigned to, or own.
Parameters:
  - p_schema: Schema name
  - p_table: Table name
  - p_user_columns: Array of column names to check (default: created_by, assigned_to, owner_id)';

-- Function: Apply complete RLS policies to a table (tenant + admin)
CREATE OR REPLACE FUNCTION apply_complete_rls_policies(
    p_schema TEXT,
    p_table TEXT,
    p_tenant_column TEXT DEFAULT 'tenant_id',
    p_include_admin_bypass BOOLEAN DEFAULT TRUE
)
RETURNS VOID AS $$
BEGIN
    -- Apply tenant isolation
    PERFORM apply_tenant_isolation_policy(p_schema, p_table, p_tenant_column);

    -- Apply admin bypass if requested
    IF p_include_admin_bypass THEN
        PERFORM apply_admin_bypass_policy(p_schema, p_table);
    END IF;

    RAISE NOTICE 'Applied complete RLS policies to %.%', p_schema, p_table;
END;
$$ LANGUAGE plpgsql;

COMMENT ON FUNCTION apply_complete_rls_policies IS
'Applies a complete set of RLS policies (tenant isolation + optional admin bypass).
Parameters:
  - p_schema: Schema name
  - p_table: Table name
  - p_tenant_column: Column name for tenant isolation (default: tenant_id)
  - p_include_admin_bypass: Whether to include admin bypass policy (default: TRUE)';

-- ============================================================================
-- EXAMPLE USAGE
-- ============================================================================

/*
-- Example 1: Apply tenant isolation to a single table
SELECT apply_tenant_isolation_policy('core', 'partners');

-- Example 2: Apply complete policies (tenant + admin) to a table
SELECT apply_complete_rls_policies('inventory', 'products');

-- Example 3: Apply user data policy
SELECT apply_user_data_policy('projects', 'tasks', ARRAY['created_by', 'assigned_to']::TEXT[]);

-- Example 4: Apply admin bypass only
SELECT apply_admin_bypass_policy('financial', 'invoices');

-- Example 5: Apply to multiple tables at once
DO $$
DECLARE
    r RECORD;
BEGIN
    FOR r IN
        SELECT table_name
        FROM information_schema.tables
        WHERE table_schema = 'core'
        AND table_name IN ('partners', 'addresses', 'notes', 'attachments')
    LOOP
        PERFORM apply_complete_rls_policies('core', r.table_name);
    END LOOP;
END $$;
*/

-- ============================================================================
-- MIGRATION HELPERS
-- ============================================================================

-- Function: Check if RLS is enabled on a table
CREATE OR REPLACE FUNCTION is_rls_enabled(p_schema TEXT, p_table TEXT)
RETURNS BOOLEAN AS $$
DECLARE
    v_enabled BOOLEAN;
BEGIN
    SELECT relrowsecurity INTO v_enabled
    FROM pg_class c
    JOIN pg_namespace n ON n.oid = c.relnamespace
    WHERE n.nspname = p_schema AND c.relname = p_table;

    RETURN COALESCE(v_enabled, FALSE);
END;
$$ LANGUAGE plpgsql STABLE;

COMMENT ON FUNCTION is_rls_enabled IS
'Check if RLS is enabled on a specific table.
Returns TRUE if enabled, FALSE otherwise.';

-- Function: List all RLS policies on a table
CREATE OR REPLACE FUNCTION list_rls_policies(p_schema TEXT, p_table TEXT)
RETURNS TABLE(policy_name NAME, policy_cmd TEXT, policy_using TEXT, policy_check TEXT) AS $$
BEGIN
    RETURN QUERY
    SELECT
        pol.polname::NAME as policy_name,
        CASE pol.polcmd
            WHEN 'r' THEN 'SELECT'
            WHEN 'a' THEN 'INSERT'
            WHEN 'w' THEN 'UPDATE'
            WHEN 'd' THEN 'DELETE'
            WHEN '*' THEN 'ALL'
        END as policy_cmd,
        pg_get_expr(pol.polqual, pol.polrelid) as policy_using,
        pg_get_expr(pol.polwithcheck, pol.polrelid) as policy_check
    FROM pg_policy pol
    JOIN pg_class c ON c.oid = pol.polrelid
    JOIN pg_namespace n ON n.oid = c.relnamespace
    WHERE n.nspname = p_schema AND c.relname = p_table;
END;
$$ LANGUAGE plpgsql STABLE;

COMMENT ON FUNCTION list_rls_policies IS
'List all RLS policies configured on a specific table.
Returns: policy_name, policy_cmd, policy_using, policy_check';

-- ============================================================================
-- END OF RLS POLICIES
-- ============================================================================