package golinters

import (
	"fmt"
	"go/ast"
	"go/types"
	"path/filepath"
	"reflect"
	"runtime"
	"sort"
	"strings"
	"sync"

	gocriticlinter "github.com/go-critic/go-critic/framework/linter"
	"golang.org/x/tools/go/analysis"

	"github.com/golangci/golangci-lint/pkg/config"
	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
	"github.com/golangci/golangci-lint/pkg/lint/linter"
	"github.com/golangci/golangci-lint/pkg/result"
)

const gocriticName = "gocritic"

func NewGocritic() *goanalysis.Linter {
	var mu sync.Mutex
	var resIssues []goanalysis.Issue

	sizes := types.SizesFor("gc", runtime.GOARCH)

	analyzer := &analysis.Analyzer{
		Name: gocriticName,
		Doc:  goanalysis.TheOnlyanalyzerDoc,
	}
	return goanalysis.NewLinter(
		gocriticName,
		`Provides many diagnostics that check for bugs, performance and style issues.
Extensible without recompilation through dynamic rules.
Dynamic rules are written declaratively with AST patterns, filters, report message and optional suggestion.`,
		[]*analysis.Analyzer{analyzer},
		nil,
	).WithContextSetter(func(lintCtx *linter.Context) {
		analyzer.Run = func(pass *analysis.Pass) (interface{}, error) {
			linterCtx := gocriticlinter.NewContext(pass.Fset, sizes)
			enabledCheckers, err := buildEnabledCheckers(lintCtx, linterCtx)
			if err != nil {
				return nil, err
			}

			linterCtx.SetPackageInfo(pass.TypesInfo, pass.Pkg)
			var res []goanalysis.Issue
			pkgIssues := runGocriticOnPackage(linterCtx, enabledCheckers, pass.Files)
			for i := range pkgIssues {
				res = append(res, goanalysis.NewIssue(&pkgIssues[i], pass))
			}
			if len(res) == 0 {
				return nil, nil
			}

			mu.Lock()
			resIssues = append(resIssues, res...)
			mu.Unlock()

			return nil, nil
		}
	}).WithIssuesReporter(func(*linter.Context) []goanalysis.Issue {
		return resIssues
	}).WithLoadMode(goanalysis.LoadModeTypesInfo)
}

func normalizeCheckerInfoParams(info *gocriticlinter.CheckerInfo) gocriticlinter.CheckerParams {
	// lowercase info param keys here because golangci-lint's config parser lowercases all strings
	ret := gocriticlinter.CheckerParams{}
	for k, v := range info.Params {
		ret[strings.ToLower(k)] = v
	}

	return ret
}

func configureCheckerInfo(info *gocriticlinter.CheckerInfo, allParams map[string]config.GocriticCheckSettings) error {
	params := allParams[strings.ToLower(info.Name)]
	if params == nil { // no config for this checker
		return nil
	}

	infoParams := normalizeCheckerInfoParams(info)
	for k, p := range params {
		v, ok := infoParams[k]
		if ok {
			v.Value = normalizeCheckerParamsValue(p)
			continue
		}

		// param `k` isn't supported
		if len(info.Params) == 0 {
			return fmt.Errorf("checker %s config param %s doesn't exist: checker doesn't have params",
				info.Name, k)
		}

		var supportedKeys []string
		for sk := range info.Params {
			supportedKeys = append(supportedKeys, sk)
		}
		sort.Strings(supportedKeys)

		return fmt.Errorf("checker %s config param %s doesn't exist, all existing: %s",
			info.Name, k, supportedKeys)
	}

	return nil
}

// normalizeCheckerParamsValue normalizes value types.
// go-critic asserts that CheckerParam.Value has some specific types,
// but the file parsers (TOML, YAML, JSON) don't create the same representation for raw type.
// then we have to convert value types into the expected value types.
// Maybe in the future, this kind of conversion will be done in go-critic itself.
//nolint:exhaustive // only 3 types (int, bool, and string) are supported by CheckerParam.Value
func normalizeCheckerParamsValue(p interface{}) interface{} {
	rv := reflect.ValueOf(p)
	switch rv.Type().Kind() {
	case reflect.Int64, reflect.Int32, reflect.Int16, reflect.Int8, reflect.Int:
		return int(rv.Int())
	case reflect.Bool:
		return rv.Bool()
	case reflect.String:
		return rv.String()
	default:
		return p
	}
}

func buildEnabledCheckers(lintCtx *linter.Context, linterCtx *gocriticlinter.Context) ([]*gocriticlinter.Checker, error) {
	s := lintCtx.Settings().Gocritic
	allParams := s.GetLowercasedParams()

	var enabledCheckers []*gocriticlinter.Checker
	for _, info := range gocriticlinter.GetCheckersInfo() {
		if !s.IsCheckEnabled(info.Name) {
			continue
		}

		if err := configureCheckerInfo(info, allParams); err != nil {
			return nil, err
		}

		c, err := gocriticlinter.NewChecker(linterCtx, info)
		if err != nil {
			return nil, err
		}
		enabledCheckers = append(enabledCheckers, c)
	}

	return enabledCheckers, nil
}

func runGocriticOnPackage(linterCtx *gocriticlinter.Context, checkers []*gocriticlinter.Checker,
	files []*ast.File) []result.Issue {
	var res []result.Issue
	for _, f := range files {
		filename := filepath.Base(linterCtx.FileSet.Position(f.Pos()).Filename)
		linterCtx.SetFileInfo(filename, f)

		issues := runGocriticOnFile(linterCtx, f, checkers)
		res = append(res, issues...)
	}
	return res
}

func runGocriticOnFile(ctx *gocriticlinter.Context, f *ast.File, checkers []*gocriticlinter.Checker) []result.Issue {
	var res []result.Issue

	for _, c := range checkers {
		// All checkers are expected to use *lint.Context
		// as read-only structure, so no copying is required.
		for _, warn := range c.Check(f) {
			pos := ctx.FileSet.Position(warn.Node.Pos())
			res = append(res, result.Issue{
				Pos:        pos,
				Text:       fmt.Sprintf("%s: %s", c.Info.Name, warn.Text),
				FromLinter: gocriticName,
			})
		}
	}

	return res
}