package generate

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

	"gopkg.in/yaml.v2"
)

var defaultConfig = &Config{
	Schema:      "schema.graphql",
	Operations:  []string{"genqlient.graphql"},
	Generated:   "generated.go",
	ContextType: "context.Context",
}

type Config struct {
	// The filename with the GraphQL schema (in SDL format); defaults to
	// schema.graphql
	Schema string `yaml:"schema"`

	// Filenames or globs with the operations for which to generate code;
	// defaults to genqlient.graphql.
	//
	// These may be .graphql files, containing the queries in SDL format, or
	// Go files, in which case any string-literal starting with (optional
	// whitespace and) the string "# @genqlient" will be extracted as a query.
	Operations []string `yaml:"operations"`

	// If set, a file at this path will be generated containing the exact
	// operations that genqlient will send to the server.
	//
	// This is useful for systems which require queries to be explicitly
	// safelisted, especially for cases like queries involving fragments where
	// it may not exactly match the input queries.  The JSON is an object of
	// the form
	//	{"operations": [{
	//		"operationName": "operationname",
	//		"query": "query operationName { ... }",
	//		"sourceLocation": "myqueriesfile.graphql",
	//	}]}
	// Keys may be added in the future.
	//
	// By default, no such file is written.
	ExportOperations string `yaml:"export_operations"`

	// The filename to which to write the generated code; defaults to
	// generated.go
	Generated string `yaml:"generated"`

	// The package name for the output code; defaults to the directory name of
	// Generated
	Package string `yaml:"package"`

	// Set to the fully-qualified name of a Go type which generated helpers
	// should accept and use as the context.Context for HTTP requests.
	//
	// Defaults to context.Context; set to the empty string to omit context
	// entirely (i.e. use context.Background()).  Must be a type which
	// implements context.Context.
	ContextType string `yaml:"context_type"`

	// If set, a function to get a graphql.Client, perhaps from the context.
	// By default, the client must be passed explicitly to each genqlient
	// generated query-helper.
	//
	// This is useful if you have a shared client, either a global, or
	// available from context, and don't want to pass it explicitly.  In this
	// case the signature of the genqlient-generated helpers will omit the
	// `graphql.Context` and they will call this function instead.
	//
	// Must be the fully-qualified name of a function which accepts a context
	// (of the type configured as ContextType (above), which defaults to
	// `context.Context`, or a function of no arguments if ContextType is set
	// to the empty string) and returns (graphql.Client, error).  If the
	// client-getter returns an error, the helper will return the error
	// without making a query.
	ClientGetter string `yaml:"client_getter"`

	// A map from GraphQL type name to Go fully-qualified type name to override
	// the Go type genqlient will use for this GraphQL type.
	//
	// This is primarily used for custom scalars, or to map builtin scalars to
	// a nonstandard type.  By default, builtin scalars are mapped to the
	// obvious Go types (String and ID to string, Int to int, Float to float64,
	// and Boolean to bool), but this setting will extend or override those
	// mappings.
	//
	// genqlient does not validate these types in any way; they must define
	// whatever logic is needed (MarshalJSON/UnmarshalJSON or JSON tags) to
	// convert to/from JSON.  For this reason, it's not recommended to use this
	// setting to map object, interface, or union types, because nothing
	// guarantees that the fields requested in the query match those present in
	// the Go type.
	//
	// To get equivalent behavior in just one query, use @genqlient(bind: ...);
	// see GenqlientDirective.Bind for more details.
	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 COMPATIBBILITY.  Use
	// them at your own risk!
	AllowBrokenFeatures bool `yaml:"allow_broken_features"`

	// Set automatically to the filename of the config file itself.
	configFilename string
}

// A TypeBinding represents a Go type to which genqlient will bind a particular
// GraphQL type.  See Config.Bind, above, for more details.
type TypeBinding struct {
	// The fully-qualified name of the Go type to which to bind.  For example:
	//	time.Time
	//  map[string]interface{}
	//	github.com/you/yourpkg/subpkg.MyType
	Type string `yaml:"type"`
	// If set, a GraphQL selection which must exactly match the fields
	// requested whenever this type is used.  Only applies if the GraphQL type
	// is a composite output type (object, interface, or union).
	//
	// This is useful if Type is a struct whose UnmarshalJSON or other methods
	// expect that you requested certain fields.  You can specify those fields
	// like
	//  MyType:
	//		type: path/to/my.GoType
	//		expect_exact_fields: "{ id name }"
	// and then genqlient will reject if you make a query
	//	{ fieldOfMytype { id title } }
	// The fields must match exactly, including the ordering: "{ name id }"
	// will be rejected.  But the arguments and directives, if any, need not
	// match.
	//
	// TODO(benkraft): Also add ExpectIncludesFields and ExpectSubsetOfFields,
	// or something, if you want to say, for example, that you have to request
	// certain fields but others are optional.
	ExpectExactFields string `yaml:"expect_exact_fields"`
}

// baseDir returns the directory of the config-file (relative to which
// all the other paths are resolved).
func (c *Config) baseDir() string {
	return filepath.Dir(c.configFilename)
}

func (c *Config) ValidateAndFillDefaults(configFilename string) error {
	c.configFilename = configFilename
	// Make paths relative to config dir
	c.Schema = filepath.Join(c.baseDir(), c.Schema)
	for i := range c.Operations {
		c.Operations[i] = filepath.Join(c.baseDir(), c.Operations[i])
	}
	c.Generated = filepath.Join(c.baseDir(), c.Generated)
	if c.ExportOperations != "" {
		c.ExportOperations = filepath.Join(c.baseDir(), c.ExportOperations)
	}

	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
}

func ReadAndValidateConfig(filename string) (*Config, error) {
	config := *defaultConfig
	if filename != "" {
		text, err := ioutil.ReadFile(filename)
		if err != nil {
			return nil, errorf(nil, "unreadable config file %v: %v", filename, err)
		}

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

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

	return &config, nil
}