package main

import (
	"fmt"
	"os"
	"os/exec"
	"regexp"
	"sort"
	"strings"

	kingpin "gopkg.in/alecthomas/kingpin.v3-unstable"
)

type LinterConfig struct {
	Command           string
	Pattern           string
	InstallFrom       string
	PartitionStrategy partitionStrategy
	IsFast            bool
	defaultEnabled    bool
}

type Linter struct {
	LinterConfig
	Name  string
	regex *regexp.Regexp
}

// NewLinter returns a new linter from a config
func NewLinter(name string, config LinterConfig) (*Linter, error) {
	if p, ok := predefinedPatterns[config.Pattern]; ok {
		config.Pattern = p
	}
	regex, err := regexp.Compile("(?m:" + config.Pattern + ")")
	if err != nil {
		return nil, err
	}
	if config.PartitionStrategy == nil {
		config.PartitionStrategy = partitionPathsAsDirectories
	}
	return &Linter{
		LinterConfig: config,
		Name:         name,
		regex:        regex,
	}, nil
}

func (l *Linter) String() string {
	return l.Name
}

var predefinedPatterns = map[string]string{
	"PATH:LINE:COL:MESSAGE": `^(?P<path>.*?\.go):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.*)$`,
	"PATH:LINE:MESSAGE":     `^(?P<path>.*?\.go):(?P<line>\d+):\s*(?P<message>.*)$`,
}

func getLinterByName(name string, overrideConf LinterConfig) *Linter {
	conf := defaultLinters[name]
	if val := overrideConf.Command; val != "" {
		conf.Command = val
	}
	if val := overrideConf.Pattern; val != "" {
		conf.Pattern = val
	}
	if val := overrideConf.InstallFrom; val != "" {
		conf.InstallFrom = val
	}
	if overrideConf.IsFast {
		conf.IsFast = true
	}
	if val := overrideConf.PartitionStrategy; val != nil {
		conf.PartitionStrategy = val
	}

	linter, _ := NewLinter(name, conf)
	return linter
}

func parseLinterConfigSpec(name string, spec string) (LinterConfig, error) {
	parts := strings.SplitN(spec, ":", 2)
	if len(parts) < 2 {
		return LinterConfig{}, fmt.Errorf("linter spec needs at least two components")
	}

	config := defaultLinters[name]
	config.Command, config.Pattern = parts[0], parts[1]
	if predefined, ok := predefinedPatterns[config.Pattern]; ok {
		config.Pattern = predefined
	}

	return config, nil
}

func makeInstallCommand(linters ...string) []string {
	cmd := []string{"get"}
	if config.VendoredLinters {
		cmd = []string{"install"}
	} else {
		if config.Update {
			cmd = append(cmd, "-u")
		}
		if config.Force {
			cmd = append(cmd, "-f")
		}
		if config.DownloadOnly {
			cmd = append(cmd, "-d")
		}
	}
	if config.Debug {
		cmd = append(cmd, "-v")
	}
	cmd = append(cmd, linters...)
	return cmd
}

func installLintersWithOneCommand(targets []string) error {
	cmd := makeInstallCommand(targets...)
	debug("go %s", strings.Join(cmd, " "))
	c := exec.Command("go", cmd...) // nolint: gas
	c.Stdout = os.Stdout
	c.Stderr = os.Stderr
	return c.Run()
}

func installLintersIndividually(targets []string) {
	failed := []string{}
	for _, target := range targets {
		cmd := makeInstallCommand(target)
		debug("go %s", strings.Join(cmd, " "))
		c := exec.Command("go", cmd...) // nolint: gas
		c.Stdout = os.Stdout
		c.Stderr = os.Stderr
		if err := c.Run(); err != nil {
			warning("failed to install %s: %s", target, err)
			failed = append(failed, target)
		}
	}
	if len(failed) > 0 {
		kingpin.Fatalf("failed to install the following linters: %s", strings.Join(failed, ", "))
	}
}

func installLinters() {
	names := make([]string, 0, len(defaultLinters))
	targets := make([]string, 0, len(defaultLinters))
	for name, config := range defaultLinters {
		if config.InstallFrom == "" {
			continue
		}
		names = append(names, name)
		targets = append(targets, config.InstallFrom)
	}
	sort.Strings(names)
	namesStr := strings.Join(names, "\n  ")
	if config.DownloadOnly {
		fmt.Printf("Downloading:\n  %s\n", namesStr)
	} else {
		fmt.Printf("Installing:\n  %s\n", namesStr)
	}
	err := installLintersWithOneCommand(targets)
	if err == nil {
		return
	}
	warning("failed to install one or more linters: %s (installing individually)", err)
	installLintersIndividually(targets)
}

func getDefaultLinters() []*Linter {
	out := []*Linter{}
	for name, config := range defaultLinters {
		linter, err := NewLinter(name, config)
		kingpin.FatalIfError(err, "invalid linter %q", name)
		out = append(out, linter)
	}
	return out
}

func defaultEnabled() []string {
	enabled := []string{}
	for name, config := range defaultLinters {
		if config.defaultEnabled {
			enabled = append(enabled, name)
		}
	}
	return enabled
}

func validateLinters(linters map[string]*Linter, config *Config) error {
	var unknownLinters []string
	for name := range linters {
		if _, isDefault := defaultLinters[name]; !isDefault {
			if _, isCustom := config.Linters[name]; !isCustom {
				unknownLinters = append(unknownLinters, name)
			}
		}
	}
	if len(unknownLinters) > 0 {
		return fmt.Errorf("unknown linters: %s", strings.Join(unknownLinters, ", "))
	}
	return nil
}

const vetPattern = `^(?:vet:.*?\.go:\s+(?P<path>.*?\.go):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.*))|(?:(?P<path>.*?\.go):(?P<line>\d+):\s*(?P<message>.*))$`

var defaultLinters = map[string]LinterConfig{
	"maligned": {
		Command:           "maligned",
		Pattern:           `^(?:[^:]+: )?(?P<path>.*?\.go):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.+)$`,
		InstallFrom:       "github.com/mdempsky/maligned",
		PartitionStrategy: partitionPathsAsPackages,
		defaultEnabled:    true,
	},
	"deadcode": {
		Command:           "deadcode",
		Pattern:           `^deadcode: (?P<path>.*?\.go):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.*)$`,
		InstallFrom:       "github.com/tsenart/deadcode",
		PartitionStrategy: partitionPathsAsDirectories,
		defaultEnabled:    true,
	},
	"dupl": {
		Command:           `dupl -plumbing -threshold {duplthreshold}`,
		Pattern:           `^(?P<path>.*?\.go):(?P<line>\d+)-\d+:\s*(?P<message>.*)$`,
		InstallFrom:       "github.com/mibk/dupl",
		PartitionStrategy: partitionPathsAsFiles,
		IsFast:            true,
	},
	"errcheck": {
		Command:           `errcheck -abspath {not_tests=-ignoretests}`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "github.com/kisielk/errcheck",
		PartitionStrategy: partitionPathsAsPackages,
		defaultEnabled:    true,
	},
	"gas": {
		Command:           `gas -fmt=csv`,
		Pattern:           `^(?P<path>.*?\.go),(?P<line>\d+),(?P<message>[^,]+,[^,]+,[^,]+)`,
		InstallFrom:       "github.com/GoASTScanner/gas",
		PartitionStrategy: partitionPathsAsFiles,
		defaultEnabled:    true,
		IsFast:            true,
	},
	"goconst": {
		Command:           `goconst -min-occurrences {min_occurrences} -min-length {min_const_length}`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "github.com/jgautheron/goconst/cmd/goconst",
		PartitionStrategy: partitionPathsAsDirectories,
		defaultEnabled:    true,
		IsFast:            true,
	},
	"gocyclo": {
		Command:           `gocyclo -over {mincyclo}`,
		Pattern:           `^(?P<cyclo>\d+)\s+\S+\s(?P<function>\S+)\s+(?P<path>.*?\.go):(?P<line>\d+):(\d+)$`,
		InstallFrom:       "github.com/alecthomas/gocyclo",
		PartitionStrategy: partitionPathsAsDirectories,
		defaultEnabled:    true,
		IsFast:            true,
	},
	"gofmt": {
		Command:           `gofmt -l -s`,
		Pattern:           `^(?P<path>.*?\.go)$`,
		PartitionStrategy: partitionPathsAsFiles,
		IsFast:            true,
	},
	"goimports": {
		Command:           `goimports -l`,
		Pattern:           `^(?P<path>.*?\.go)$`,
		InstallFrom:       "golang.org/x/tools/cmd/goimports",
		PartitionStrategy: partitionPathsAsFiles,
		IsFast:            true,
	},
	"golint": {
		Command:           `golint -min_confidence {min_confidence}`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "github.com/golang/lint/golint",
		PartitionStrategy: partitionPathsAsDirectories,
		defaultEnabled:    true,
		IsFast:            true,
	},
	"gosimple": {
		Command:           `gosimple`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "honnef.co/go/tools/cmd/gosimple",
		PartitionStrategy: partitionPathsAsPackages,
	},
	"gotype": {
		Command:           `gotype -e {tests=-t}`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "golang.org/x/tools/cmd/gotype",
		PartitionStrategy: partitionPathsByDirectory,
		defaultEnabled:    true,
		IsFast:            true,
	},
	"gotypex": {
		Command:           `gotype -e -x`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "golang.org/x/tools/cmd/gotype",
		PartitionStrategy: partitionPathsByDirectory,
		defaultEnabled:    true,
		IsFast:            true,
	},
	"ineffassign": {
		Command:           `ineffassign -n`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "github.com/gordonklaus/ineffassign",
		PartitionStrategy: partitionPathsAsDirectories,
		defaultEnabled:    true,
		IsFast:            true,
	},
	"interfacer": {
		Command:           `interfacer`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "mvdan.cc/interfacer",
		PartitionStrategy: partitionPathsAsPackages,
		defaultEnabled:    true,
	},
	"lll": {
		Command:           `lll -g -l {maxlinelength}`,
		Pattern:           `PATH:LINE:MESSAGE`,
		InstallFrom:       "github.com/walle/lll/cmd/lll",
		PartitionStrategy: partitionPathsAsFiles,
		IsFast:            true,
	},
	"megacheck": {
		Command:           `megacheck`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "honnef.co/go/tools/cmd/megacheck",
		PartitionStrategy: partitionPathsAsPackages,
		defaultEnabled:    true,
	},
	"misspell": {
		Command:           `misspell -j 1 --locale "{misspelllocale}"`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "github.com/client9/misspell/cmd/misspell",
		PartitionStrategy: partitionPathsAsFiles,
		IsFast:            true,
	},
	"nakedret": {
		Command:           `nakedret`,
		Pattern:           `^(?P<path>.*?\.go):(?P<line>\d+)\s*(?P<message>.*)$`,
		InstallFrom:       "github.com/alexkohler/nakedret",
		PartitionStrategy: partitionPathsAsDirectories,
	},
	"safesql": {
		Command:           `safesql`,
		Pattern:           `^- (?P<path>.*?\.go):(?P<line>\d+):(?P<col>\d+)$`,
		InstallFrom:       "github.com/stripe/safesql",
		PartitionStrategy: partitionPathsAsPackages,
	},
	"staticcheck": {
		Command:           `staticcheck`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "honnef.co/go/tools/cmd/staticcheck",
		PartitionStrategy: partitionPathsAsPackages,
	},
	"structcheck": {
		Command:           `structcheck {tests=-t}`,
		Pattern:           `^(?:[^:]+: )?(?P<path>.*?\.go):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.+)$`,
		InstallFrom:       "github.com/opennota/check/cmd/structcheck",
		PartitionStrategy: partitionPathsAsPackages,
		defaultEnabled:    true,
	},
	"test": {
		Command:           `go test`,
		Pattern:           `^--- FAIL: .*$\s+(?P<path>.*?\.go):(?P<line>\d+): (?P<message>.*)$`,
		PartitionStrategy: partitionPathsAsPackages,
	},
	"testify": {
		Command:           `go test`,
		Pattern:           `Location:\s+(?P<path>.*?\.go):(?P<line>\d+)$\s+Error:\s+(?P<message>[^\n]+)`,
		PartitionStrategy: partitionPathsAsPackages,
	},
	"unconvert": {
		Command:           `unconvert`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "github.com/mdempsky/unconvert",
		PartitionStrategy: partitionPathsAsPackages,
		defaultEnabled:    true,
	},
	"unparam": {
		Command:           `unparam {not_tests=-tests=false}`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "mvdan.cc/unparam",
		PartitionStrategy: partitionPathsAsPackages,
	},
	"unused": {
		Command:           `unused`,
		Pattern:           `PATH:LINE:COL:MESSAGE`,
		InstallFrom:       "honnef.co/go/tools/cmd/unused",
		PartitionStrategy: partitionPathsAsPackages,
	},
	"varcheck": {
		Command:           `varcheck`,
		Pattern:           `^(?:[^:]+: )?(?P<path>.*?\.go):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.*)$`,
		InstallFrom:       "github.com/opennota/check/cmd/varcheck",
		PartitionStrategy: partitionPathsAsPackages,
		defaultEnabled:    true,
	},
	"vet": {
		Command:           `govet --no-recurse`,
		Pattern:           vetPattern,
		InstallFrom:       "github.com/dnephin/govet",
		PartitionStrategy: partitionPathsAsDirectories,
		defaultEnabled:    true,
		IsFast:            true,
	},
	"vetshadow": {
		Command:           `govet --no-recurse --shadow`,
		Pattern:           vetPattern,
		PartitionStrategy: partitionPathsAsDirectories,
		defaultEnabled:    true,
		IsFast:            true,
	},
}