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package main

/*
#cgo LDFLAGS: -lsqlite3
#include <sqlite3.h>
#include <stdlib.h>
#include <string.h>

// Open a database file and return a handle.
int db_open(const char *path, sqlite3 **db) {
    return sqlite3_open(path, db);
}

// Execute a statement that returns no rows.
int db_exec(sqlite3 *db, const char *sql, char **errmsg) {
    return sqlite3_exec(db, sql, NULL, NULL, errmsg);
}

// Prepare a statement.
int db_prepare(sqlite3 *db, const char *sql, sqlite3_stmt **stmt) {
    return sqlite3_prepare_v2(db, sql, -1, stmt, NULL);
}

// Bind a text parameter (1-based index). Makes a private copy.
int db_bind_text(sqlite3_stmt *stmt, int idx, const char *val) {
    return sqlite3_bind_text(stmt, idx, val, -1, SQLITE_TRANSIENT);
}

// Step the statement.
int db_step(sqlite3_stmt *stmt) {
    return sqlite3_step(stmt);
}

// Retrieve a text column value.
const char *db_column_text(sqlite3_stmt *stmt, int col) {
    return (const char *)sqlite3_column_text(stmt, col);
}

// Finalize the statement.
int db_finalize(sqlite3_stmt *stmt) {
    return sqlite3_finalize(stmt);
}

// Close the database.
int db_close(sqlite3 *db) {
    return sqlite3_close(db);
}

// Return the last error message.
const char *db_errmsg(sqlite3 *db) {
    return sqlite3_errmsg(db);
}
*/
import "C"
import (
	"fmt"
	"unsafe"
)

// DB wraps a raw sqlite3 pointer.
type DB struct {
	ptr *C.sqlite3
}

// openDB opens (or creates) the SQLite file at path.
func openDB(path string) (*DB, error) {
	cpath := C.CString(path)
	defer C.free(unsafe.Pointer(cpath))

	var ptr *C.sqlite3
	rc := C.db_open(cpath, &ptr)
	if rc != C.SQLITE_OK {
		return nil, fmt.Errorf("sqlite3_open: code %d", rc)
	}
	return &DB{ptr: ptr}, nil
}

// Close closes the database connection.
func (db *DB) Close() {
	if db.ptr != nil {
		C.db_close(db.ptr)
		db.ptr = nil
	}
}

// Exec runs a statement that returns no rows (DDL, INSERT, etc.).
func (db *DB) Exec(sql string, args ...string) error {
	if len(args) == 0 {
		csql := C.CString(sql)
		defer C.free(unsafe.Pointer(csql))
		var errmsg *C.char
		rc := C.db_exec(db.ptr, csql, &errmsg)
		if rc != C.SQLITE_OK {
			msg := C.GoString(errmsg)
			C.sqlite3_free(unsafe.Pointer(errmsg))
			return fmt.Errorf("exec: %s", msg)
		}
		return nil
	}

	// Prepared statement path
	csql := C.CString(sql)
	defer C.free(unsafe.Pointer(csql))
	var stmt *C.sqlite3_stmt
	rc := C.db_prepare(db.ptr, csql, &stmt)
	if rc != C.SQLITE_OK {
		return fmt.Errorf("prepare: %s", C.GoString(C.db_errmsg(db.ptr)))
	}
	defer C.db_finalize(stmt)

	for i, arg := range args {
		carg := C.CString(arg)
		rc = C.db_bind_text(stmt, C.int(i+1), carg)
		C.free(unsafe.Pointer(carg))
		if rc != C.SQLITE_OK {
			return fmt.Errorf("bind[%d]: %s", i, C.GoString(C.db_errmsg(db.ptr)))
		}
	}

	rc = C.db_step(stmt)
	if rc != C.SQLITE_DONE {
		return fmt.Errorf("step: %s", C.GoString(C.db_errmsg(db.ptr)))
	}
	return nil
}

// Row is a map of column-name → string value.
type Row map[string]string

// Query runs a SELECT and returns all rows.
func (db *DB) Query(sql string, args ...string) ([]Row, error) {
	csql := C.CString(sql)
	defer C.free(unsafe.Pointer(csql))

	var stmt *C.sqlite3_stmt
	rc := C.db_prepare(db.ptr, csql, &stmt)
	if rc != C.SQLITE_OK {
		return nil, fmt.Errorf("prepare: %s", C.GoString(C.db_errmsg(db.ptr)))
	}
	defer C.db_finalize(stmt)

	for i, arg := range args {
		carg := C.CString(arg)
		rc = C.db_bind_text(stmt, C.int(i+1), carg)
		C.free(unsafe.Pointer(carg))
		if rc != C.SQLITE_OK {
			return nil, fmt.Errorf("bind[%d]: %s", i, C.GoString(C.db_errmsg(db.ptr)))
		}
	}

	colCount := int(C.sqlite3_column_count(stmt))
	colNames := make([]string, colCount)
	for i := 0; i < colCount; i++ {
		colNames[i] = C.GoString(C.sqlite3_column_name(stmt, C.int(i)))
	}

	var rows []Row
	for {
		rc = C.db_step(stmt)
		if rc == C.SQLITE_DONE {
			break
		}
		if rc != C.SQLITE_ROW {
			return nil, fmt.Errorf("step: %s", C.GoString(C.db_errmsg(db.ptr)))
		}
		row := make(Row, colCount)
		for i := 0; i < colCount; i++ {
			row[colNames[i]] = C.GoString(C.db_column_text(stmt, C.int(i)))
		}
		rows = append(rows, row)
	}
	return rows, nil
}