// Copyright 2019 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 cache

import (
	"context"
	"go/ast"
	"sync"

	"golang.org/x/tools/internal/lsp/source"
	"golang.org/x/tools/internal/lsp/telemetry"
	errors "golang.org/x/xerrors"
)

// goFile holds all of the information we know about a Go file.
type goFile struct {
	fileBase

	// mu protects all mutable state of the Go file,
	// which can be modified during type-checking.
	mu sync.Mutex

	// missingImports is the set of unresolved imports for this package.
	// It contains any packages with `go list` errors.
	missingImports map[packagePath]struct{}

	imports []*ast.ImportSpec

	cphs map[packageKey]*checkPackageHandle
	meta map[packageID]*metadata
}

type packageKey struct {
	id   packageID
	mode source.ParseMode
}

func (f *goFile) CheckPackageHandles(ctx context.Context) ([]source.CheckPackageHandle, error) {
	ctx = telemetry.File.With(ctx, f.URI())
	fh := f.Handle(ctx)

	if f.isDirty(ctx, fh) {
		if err := f.view.loadParseTypecheck(ctx, f, fh); err != nil {
			return nil, err
		}
	}

	f.mu.Lock()
	defer f.mu.Unlock()

	var results []source.CheckPackageHandle
	seenIDs := make(map[string]bool)
	for _, cph := range f.cphs {
		if seenIDs[cph.ID()] {
			continue
		}
		if cph.mode() < source.ParseFull {
			continue
		}
		results = append(results, cph)
		seenIDs[cph.ID()] = true
	}
	if len(results) == 0 {
		return nil, errors.Errorf("no CheckPackageHandles for %s", f.URI())
	}
	return results, nil
}

func (f *goFile) GetActiveReverseDeps(ctx context.Context) (files []source.GoFile) {
	seen := make(map[packageID]struct{}) // visited packages
	results := make(map[*goFile]struct{})

	f.view.mu.Lock()
	defer f.view.mu.Unlock()

	f.view.mcache.mu.Lock()
	defer f.view.mcache.mu.Unlock()

	for _, m := range f.metadata() {
		f.view.reverseDeps(ctx, seen, results, m.id)
		for f := range results {
			if f == nil {
				continue
			}
			// Don't return any of the active files in this package.
			f.mu.Lock()
			_, ok := f.meta[m.id]
			f.mu.Unlock()
			if ok {
				continue
			}

			files = append(files, f)
		}
	}
	return files
}

func (v *view) reverseDeps(ctx context.Context, seen map[packageID]struct{}, results map[*goFile]struct{}, id packageID) {
	if _, ok := seen[id]; ok {
		return
	}
	seen[id] = struct{}{}
	m, ok := v.mcache.packages[id]
	if !ok {
		return
	}
	for _, uri := range m.files {
		// Call unlocked version of getFile since we hold the lock on the view.
		if f, err := v.getFile(ctx, uri, source.Go); err == nil && v.session.IsOpen(uri) {
			results[f.(*goFile)] = struct{}{}
		}
	}
	for parentID := range m.parents {
		v.reverseDeps(ctx, seen, results, parentID)
	}
}

// metadata assumes that the caller holds the f.mu lock.
func (f *goFile) metadata() []*metadata {
	result := make([]*metadata, 0, len(f.meta))
	for _, m := range f.meta {
		result = append(result, m)
	}
	return result
}

// isDirty is true if the file needs to be type-checked.
// It assumes that the file's view's mutex is held by the caller.
func (f *goFile) isDirty(ctx context.Context, fh source.FileHandle) bool {
	f.mu.Lock()
	defer f.mu.Unlock()

	if len(f.meta) == 0 || len(f.cphs) == 0 {
		return true
	}
	if len(f.missingImports) > 0 {
		return true
	}
	for key, cph := range f.cphs {
		if key.mode != source.ParseFull {
			continue
		}
		for _, file := range cph.Files() {
			if file.File().Identity() == fh.Identity() {
				return false
			}
		}
	}
	return true
}