// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package source

import (
	"fmt"
	"go/ast"
	"go/token"
	"io/ioutil"

	"golang.org/x/tools/go/packages"
)

// File holds all the information we know about a file.
type File struct {
	URI     URI
	view    *View
	active  bool
	content []byte
	ast     *ast.File
	token   *token.File
	pkg     *packages.Package
}

// Range represents a start and end position.
// Because Range is based purely on two token.Pos entries, it is not self
// contained. You need access to a token.FileSet to regain the file
// information.
type Range struct {
	Start token.Pos
	End   token.Pos
}

// TextEdit represents a change to a section of a document.
// The text within the specified range should be replaced by the supplied new text.
type TextEdit struct {
	Range   Range
	NewText string
}

// SetContent sets the overlay contents for a file.
// Setting it to nil will revert it to the on disk contents, and remove it
// from the active set.
func (f *File) SetContent(content []byte) {
	f.view.mu.Lock()
	defer f.view.mu.Unlock()
	f.content = content
	// the ast and token fields are invalid
	f.ast = nil
	f.token = nil
	f.pkg = nil
	// and we might need to update the overlay
	switch {
	case f.active && content == nil:
		// we were active, and want to forget the content
		f.active = false
		if filename, err := f.URI.Filename(); err == nil {
			delete(f.view.Config.Overlay, filename)
		}
		f.content = nil
	case content != nil:
		// an active overlay, update the map
		f.active = true
		if filename, err := f.URI.Filename(); err == nil {
			f.view.Config.Overlay[filename] = f.content
		}
	}
}

// Read returns the contents of the file, reading it from file system if needed.
func (f *File) Read() ([]byte, error) {
	f.view.mu.Lock()
	defer f.view.mu.Unlock()
	return f.read()
}

func (f *File) GetToken() (*token.File, error) {
	f.view.mu.Lock()
	defer f.view.mu.Unlock()
	if f.token == nil {
		if err := f.view.parse(f.URI); err != nil {
			return nil, err
		}
		if f.token == nil {
			return nil, fmt.Errorf("failed to find or parse %v", f.URI)
		}
	}
	return f.token, nil
}

func (f *File) GetAST() (*ast.File, error) {
	f.view.mu.Lock()
	defer f.view.mu.Unlock()
	if f.ast == nil {
		if err := f.view.parse(f.URI); err != nil {
			return nil, err
		}
	}
	return f.ast, nil
}

func (f *File) GetPackage() (*packages.Package, error) {
	f.view.mu.Lock()
	defer f.view.mu.Unlock()
	if f.pkg == nil {
		if err := f.view.parse(f.URI); err != nil {
			return nil, err
		}
	}
	return f.pkg, nil
}

// read is the internal part of Read that presumes the lock is already held
func (f *File) read() ([]byte, error) {
	if f.content != nil {
		return f.content, nil
	}
	// we don't know the content yet, so read it
	filename, err := f.URI.Filename()
	if err != nil {
		return nil, err
	}
	content, err := ioutil.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	f.content = content
	return f.content, nil
}