// 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 mod provides core features related to go.mod file
// handling for use by Go editors and tools.
package mod

import (
	"context"

	"golang.org/x/tools/internal/lsp/protocol"
	"golang.org/x/tools/internal/lsp/source"
	"golang.org/x/tools/internal/lsp/telemetry"
	"golang.org/x/tools/internal/telemetry/log"
	"golang.org/x/tools/internal/telemetry/trace"
)

func Diagnostics(ctx context.Context, snapshot source.Snapshot) (map[source.FileIdentity][]source.Diagnostic, error) {
	// TODO: We will want to support diagnostics for go.mod files even when the -modfile flag is turned off.
	realURI, tempURI, err := snapshot.View().ModFiles()
	if err != nil {
		return nil, err
	}
	// Check the case when the tempModfile flag is turned off.
	if realURI == "" || tempURI == "" {
		return nil, nil
	}

	ctx, done := trace.StartSpan(ctx, "mod.Diagnostics", telemetry.File.Of(realURI))
	defer done()

	realfh, err := snapshot.GetFile(realURI)
	if err != nil {
		return nil, err
	}
	_, _, parseErrors, err := snapshot.ModTidyHandle(ctx, realfh).Tidy(ctx)
	if err != nil {
		return nil, err
	}

	reports := map[source.FileIdentity][]source.Diagnostic{
		realfh.Identity(): []source.Diagnostic{},
	}
	for _, e := range parseErrors {
		diag := source.Diagnostic{
			Message:        e.Message,
			Range:          e.Range,
			SuggestedFixes: e.SuggestedFixes,
			Source:         e.Category,
		}
		if e.Category == "syntax" {
			diag.Severity = protocol.SeverityError
		} else {
			diag.Severity = protocol.SeverityWarning
		}
		reports[realfh.Identity()] = append(reports[realfh.Identity()], diag)
	}
	return reports, nil
}

func SuggestedFixes(ctx context.Context, snapshot source.Snapshot, f source.FileHandle, diags []protocol.Diagnostic) []protocol.CodeAction {
	_, _, parseErrors, err := snapshot.ModTidyHandle(ctx, f).Tidy(ctx)
	if err != nil {
		return nil
	}

	errorsMap := make(map[string][]source.Error)
	for _, e := range parseErrors {
		if errorsMap[e.Message] == nil {
			errorsMap[e.Message] = []source.Error{}
		}
		errorsMap[e.Message] = append(errorsMap[e.Message], e)
	}

	var actions []protocol.CodeAction
	for _, diag := range diags {
		for _, e := range errorsMap[diag.Message] {
			if !sameDiagnostic(diag, e) {
				continue
			}
			for _, fix := range e.SuggestedFixes {
				action := protocol.CodeAction{
					Title:       fix.Title,
					Kind:        protocol.QuickFix,
					Diagnostics: []protocol.Diagnostic{diag},
					Edit:        protocol.WorkspaceEdit{},
				}
				for uri, edits := range fix.Edits {
					fh, err := snapshot.GetFile(uri)
					if err != nil {
						log.Error(ctx, "no file", err, telemetry.URI.Of(uri))
						continue
					}
					action.Edit.DocumentChanges = append(action.Edit.DocumentChanges, protocol.TextDocumentEdit{
						TextDocument: protocol.VersionedTextDocumentIdentifier{
							Version: fh.Identity().Version,
							TextDocumentIdentifier: protocol.TextDocumentIdentifier{
								URI: protocol.NewURI(fh.Identity().URI),
							},
						},
						Edits: edits,
					})
				}
				actions = append(actions, action)
			}
		}
	}
	return actions
}

func sameDiagnostic(d protocol.Diagnostic, e source.Error) bool {
	return d.Message == e.Message && protocol.CompareRange(d.Range, e.Range) == 0 && d.Source == e.Category
}