elliotchance/gedcom

package q

import (
    "fmt"

    "github.com/elliotchance/gedcom/v39"
)

// Engine is the compiled query. It is able to evaluate the entire query.
type Engine struct {
    Statements []*Statement
}

// Evaluate executes all of the expressions and returns the final result.
//
// Evaluate expects that there is at least one document provided.
func (e *Engine) Evaluate(documents []*gedcom.Document) (interface{}, error) {
    // Before we begin we will setup the Document variables. Each document, in
    // order will be given Document1, Document2, ...
    for i, document := range documents {
        // Always prepend. The order of these variables does not matter, but we
        // need to make sure they do not land on the end where they will attempt
        // to be evaluated as the result.
        e.Statements = append([]*Statement{{
            VariableName: fmt.Sprintf("Document%d", i+1),
            Expressions: []Expression{
                &ValueExpr{Value: document},
            },
        }}, e.Statements...)
    }

    firstDocument := documents[0]

    for _, statement := range e.Statements {
        _, err := statement.Evaluate(e, firstDocument)

        if err != nil {
            return nil, err
        }
    }

    // ghost:ignore
    lastStatement := e.Statements[len(e.Statements)-1]

    return lastStatement.Evaluate(e, firstDocument)
}

func (e *Engine) StatementByVariableName(name string) (*Statement, error) {
    for _, variable := range e.Statements {
        if variable.VariableName == name {
            return variable, nil
        }
    }

    return nil, fmt.Errorf("no such variable %s", name)
}