package generate

import (
	"go/token"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"

	"gopkg.in/yaml.v2"
)

// Config represents genqlient's configuration, generally read from
// genqlient.yaml.
//
// Callers must call ValidateAndFillDefaults before using the config.
type Config struct {
	// The following fields are documented at:
	// https://github.com/Khan/genqlient/blob/main/docs/genqlient.yaml
	Schema           string                  `yaml:"schema"`
	Operations       []string                `yaml:"operations"`
	Generated        string                  `yaml:"generated"`
	Package          string                  `yaml:"package"`
	ExportOperations string                  `yaml:"export_operations"`
	ContextType      string                  `yaml:"context_type"`
	ClientGetter     string                  `yaml:"client_getter"`
	Bindings         map[string]*TypeBinding `yaml:"bindings"`

	// Set to true to use features that aren't fully ready to use.
	//
	// This is primarily intended for genqlient's own tests.  These features
	// are likely BROKEN and come with NO EXPECTATION OF COMPATIBILITY.  Use
	// them at your own risk!
	AllowBrokenFeatures bool `yaml:"allow_broken_features"`

	// The directory of the config-file (relative to which all the other paths
	// are resolved).  Set by ValidateAndFillDefaults.
	baseDir string
}

// A TypeBinding represents a Go type to which genqlient will bind a particular
// GraphQL type, and is documented further at:
// https://github.com/Khan/genqlient/blob/main/docs/genqlient.yaml
type TypeBinding struct {
	Type              string `yaml:"type"`
	ExpectExactFields string `yaml:"expect_exact_fields"`
}

// ValidateAndFillDefaults ensures that the configuration is valid, and fills
// in any options that were unspecified.
//
// The argument is the directory relative to which paths will be interpreted,
// typically the directory of the config file.
func (c *Config) ValidateAndFillDefaults(baseDir string) error {
	c.baseDir = baseDir
	// Make paths relative to config dir
	c.Schema = filepath.Join(baseDir, c.Schema)
	for i := range c.Operations {
		c.Operations[i] = filepath.Join(baseDir, c.Operations[i])
	}
	c.Generated = filepath.Join(baseDir, c.Generated)
	if c.ExportOperations != "" {
		c.ExportOperations = filepath.Join(baseDir, c.ExportOperations)
	}

	if c.ContextType == "" {
		c.ContextType = "context.Context"
	}

	if c.Package == "" {
		abs, err := filepath.Abs(c.Generated)
		if err != nil {
			return errorf(nil, "unable to guess package-name: %v", err)
		}

		base := filepath.Base(filepath.Dir(abs))
		if !token.IsIdentifier(base) {
			return errorf(nil, "unable to guess package-name: %v is not a valid identifier", base)
		}

		c.Package = base
	}

	return nil
}

// ReadAndValidateConfig reads the configuration from the given file, validates
// it, and returns it.
func ReadAndValidateConfig(filename string) (*Config, error) {
	text, err := ioutil.ReadFile(filename)
	if err != nil {
		return nil, errorf(nil, "unreadable config file %v: %v", filename, err)
	}

	var config Config
	err = yaml.UnmarshalStrict(text, &config)
	if err != nil {
		return nil, errorf(nil, "invalid config file %v: %v", filename, err)
	}

	err = config.ValidateAndFillDefaults(filepath.Dir(filename))
	if err != nil {
		return nil, errorf(nil, "invalid config file %v: %v", filename, err)
	}

	return &config, nil
}

func initConfig(filename string) error {
	// TODO(benkraft): Embed this config file into the binary, see
	// https://github.com/Khan/genqlient/issues/9.
	r, err := os.Open(filepath.Join(thisDir, "default_genqlient.yaml"))
	if err != nil {
		return err
	}
	w, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o644)
	if err != nil {
		return err
	}
	_, err = io.Copy(w, r)
	return err
}