package main

import (
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"
	"strings"
)

var queueName = regexp.MustCompile(`^[A-Za-z0-9_.@-]{1,127}$`)

func checkPrinter(p string) error {
	if !queueName.MatchString(p) || strings.HasPrefix(p, "-") {
		return fmt.Errorf("%q is not a printer queue's name", p)
	}
	return nil
}

var optionName = regexp.MustCompile(`^[a-z][a-z0-9-]{0,63}$`)
var optionValue = regexp.MustCompile(`^[A-Za-z0-9._:-]{1,128}$`)

// optionsOf reads the print options object.
func optionsOf(args map[string]any) (map[string]string, error) {
	v, ok := args["options"]
	if !ok || v == nil {
		return nil, nil
	}
	m, ok := v.(map[string]any)
	if !ok {
		return nil, fmt.Errorf("options must be an object of names to values")
	}
	out := map[string]string{}
	for k, val := range m {
		s, ok := val.(string)
		if !ok || !optionName.MatchString(k) || !optionValue.MatchString(s) {
			return nil, fmt.Errorf("option %s=%v is not an IPP option name and a plain value", k, val)
		}
		out[k] = s
	}
	return out, nil
}

// lpoptionsOf reads lpoptions' answer: name=value pairs, a value quoted with ' or with backslash escapes.
func lpoptionsOf(s string) map[string]string {
	out := map[string]string{}
	s = strings.TrimSpace(s)
	i := 0
	for i < len(s) {
		for i < len(s) && s[i] == ' ' {
			i++
		}
		start := i
		for i < len(s) && s[i] != '=' && s[i] != ' ' {
			i++
		}
		key := s[start:i]
		if i >= len(s) || s[i] != '=' {
			if key != "" {
				out[key] = ""
			}
			continue
		}
		i++
		var b strings.Builder
		for i < len(s) && s[i] != ' ' {
			switch s[i] {
			case '\'':
				i++
				for i < len(s) && s[i] != '\'' {
					if s[i] == '\\' && i+1 < len(s) {
						i++
					}
					b.WriteByte(s[i])
					i++
				}
				i++
			case '\\':
				if i+1 < len(s) {
					b.WriteByte(s[i+1])
				}
				i += 2
			default:
				b.WriteByte(s[i])
				i++
			}
		}
		out[key] = b.String()
	}
	return out
}

// Marker is one supply the printer reports.
type Marker struct {
	Name  string `json:"name"`
	Type  string `json:"type,omitempty"`
	Level int    `json:"level_percent"`
	Low   bool   `json:"low"`
}

// Printer is one queue.
type Printer struct {
	Name       string   `json:"name"`
	State      string   `json:"state"`
	Enabled    bool     `json:"enabled"`
	Accepting  bool     `json:"accepting"`
	Default    bool     `json:"default"`
	URI        string   `json:"uri"`
	MakeModel  string   `json:"make_and_model"`
	Driverless bool     `json:"driverless"`
	Shared     bool     `json:"shared"`
	Reasons    []string `json:"reasons"`
	Markers    []Marker `json:"markers"`
	Since      string   `json:"since,omitempty"`
	Message    string   `json:"message,omitempty"`
}

// PrintersAnswer is what cups_printers answers.
type PrintersAnswer struct {
	Scheduler string    `json:"scheduler"`
	Default   string    `json:"default,omitempty"`
	Printers  []Printer `json:"printers"`
}

func lpstat(args ...string) (string, error) {
	r, err := call(Cmd{Name: "lpstat", Args: args})
	if err != nil {
		if strings.Contains(r.Stderr, "Scheduler is not running") || strings.Contains(r.Stderr, "Connection refused") {
			return "", fmt.Errorf("the print scheduler is not running on this machine: %s", firstLine(r.Stderr))
		}
		// lpstat answers "No destinations added." with a non-zero status: that is no printers.
		if strings.Contains(r.Stderr, "No destinations added") {
			return "", nil
		}
		return "", err
	}
	return r.Stdout, nil
}

func defaultPrinter() (string, error) {
	out, err := lpstat("-d")
	if err != nil {
		return "", err
	}
	if _, after, ok := strings.Cut(out, "system default destination: "); ok {
		return strings.TrimSpace(firstLine(after)), nil
	}
	return "", nil
}

// Printers answers every queue with its state, device, model and supplies.
func Printers() (PrintersAnswer, error) {
	out := PrintersAnswer{Printers: []Printer{}}
	sched, err := lpstat("-r")
	if err != nil {
		return out, err
	}
	out.Scheduler = strings.TrimSpace(sched)
	if out.Default, err = defaultPrinter(); err != nil {
		return out, err
	}
	ps, err := lpstat("-p")
	if err != nil {
		return out, err
	}
	var cur *Printer
	for _, l := range strings.Split(ps, "\n") {
		if strings.HasPrefix(l, "printer ") {
			f := strings.Fields(l)
			if len(f) < 3 {
				continue
			}
			out.Printers = append(out.Printers, Printer{Name: f[1], Reasons: []string{}, Markers: []Marker{}})
			cur = &out.Printers[len(out.Printers)-1]
			rest := strings.Join(f[2:], " ")
			switch {
			case strings.HasPrefix(rest, "is idle"):
				cur.State = "idle"
			case strings.HasPrefix(rest, "now printing"):
				cur.State = "printing"
			default:
				cur.State = "stopped"
			}
			// "disabled since …" (stopped), or "enabled since …" after the state.
			cur.Enabled = !strings.HasPrefix(rest, "disabled") && !strings.Contains(rest, "disabled since")
			if _, since, found := strings.Cut(rest, " since "); found {
				cur.Since = strings.TrimSuffix(strings.TrimSpace(since), " -")
			}
			continue
		}
		if cur != nil && strings.HasPrefix(l, "\t") && strings.TrimSpace(l) != "" {
			cur.Message = strings.TrimSpace(cur.Message + " " + strings.TrimSpace(l))
		}
	}
	acc, err := lpstat("-a")
	if err != nil {
		return out, err
	}
	accepting := map[string]bool{}
	for _, l := range lines(acc) {
		if f := strings.Fields(l); len(f) >= 2 && f[1] == "accepting" {
			accepting[f[0]] = true
		}
	}
	for i := range out.Printers {
		p := &out.Printers[i]
		p.Accepting = accepting[p.Name]
		p.Default = p.Name == out.Default
		r, err := call(Cmd{Name: "lpoptions", Args: []string{"-p", p.Name}})
		if err != nil {
			return out, err
		}
		o := lpoptionsOf(r.Stdout)
		p.URI = o["device-uri"]
		p.MakeModel = o["printer-make-and-model"]
		p.Driverless = driverless(p.MakeModel, p.URI)
		p.Shared = o["printer-is-shared"] == "true"
		for _, reason := range strings.Split(o["printer-state-reasons"], ",") {
			if reason = strings.TrimSpace(reason); reason != "" && reason != "none" {
				p.Reasons = append(p.Reasons, reason)
			}
		}
		p.Markers = markersOf(o)
	}
	return out, nil
}

// driverless says a queue prints without a vendor driver: CUPS's own IPP Everywhere model, or a
// driverless URI.
func driverless(model, uri string) bool {
	m := strings.ToLower(model)
	return strings.Contains(m, "ipp everywhere") || strings.Contains(m, "driverless") || strings.HasPrefix(uri, "implicitclass:") ||
		strings.HasPrefix(uri, "ipp://") && strings.Contains(m, "everywhere")
}

func markersOf(o map[string]string) []Marker {
	split := func(k string) []string {
		if o[k] == "" {
			return nil
		}
		return strings.Split(o[k], ",")
	}
	names, levels, lows, types := split("marker-names"), split("marker-levels"), split("marker-low-levels"), split("marker-types")
	out := []Marker{}
	for i, n := range names {
		if i >= len(levels) {
			break
		}
		level, err := strconv.Atoi(strings.TrimSpace(levels[i]))
		if err != nil {
			continue
		}
		m := Marker{Name: strings.TrimSpace(n), Level: level}
		if i < len(types) {
			m.Type = strings.TrimSpace(types[i])
		}
		if i < len(lows) {
			if low, err := strconv.Atoi(strings.TrimSpace(lows[i])); err == nil && level >= 0 && level <= low {
				m.Low = true
			}
		}
		out = append(out, m)
	}
	return out
}

// Job is one print job.
type Job struct {
	ID        string `json:"id"`
	Printer   string `json:"printer"`
	User      string `json:"user"`
	Bytes     int64  `json:"bytes"`
	Submitted string `json:"submitted"`
}

// Queue answers the jobs waiting, or the finished ones.
func Queue(printer string, completed bool, limit int) (map[string]any, error) {
	args := []string{}
	if completed {
		args = append(args, "-W", "completed")
	}
	args = append(args, "-o")
	if printer != "" {
		if err := checkPrinter(printer); err != nil {
			return nil, err
		}
		args = append(args, printer)
	}
	out, err := lpstat(args...)
	if err != nil {
		return nil, err
	}
	jobs := []Job{}
	for _, l := range lines(out) {
		f := strings.Fields(l)
		if len(f) < 4 {
			continue
		}
		i := strings.LastIndex(f[0], "-")
		if i <= 0 {
			continue
		}
		size, _ := strconv.ParseInt(f[2], 10, 64)
		jobs = append(jobs, Job{ID: f[0], Printer: f[0][:i], User: f[1], Bytes: size, Submitted: strings.Join(f[3:], " ")})
	}
	sort.SliceStable(jobs, func(a, b int) bool { return jobNumber(jobs[a].ID) > jobNumber(jobs[b].ID) })
	total := len(jobs)
	if len(jobs) > limit {
		jobs = jobs[:limit]
	}
	return map[string]any{"count": total, "jobs": jobs, "completed": completed}, nil
}

func jobNumber(id string) int {
	n, _ := strconv.Atoi(id[strings.LastIndex(id, "-")+1:])
	return n
}

var jobID = regexp.MustCompile(`^([A-Za-z0-9_.@-]+-)?[0-9]+$`)

// refused says CUPS kept an act for its administrators.
func refused(r Result) bool {
	s := r.Stderr + r.Stdout
	return strings.Contains(s, "Forbidden") || strings.Contains(s, "not-authorized") || strings.Contains(s, "Not authorized") || strings.Contains(s, "not allowed")
}

// asAccountThenRoot runs an act as the account, and through sudo -n when CUPS refuses the account.
func asAccountThenRoot(c Cmd) (Result, bool, error) {
	r := run(c)
	if r.Status == 0 && r.Error == "" {
		return r, false, nil
	}
	if !refused(r) {
		return r, false, failure(c, r)
	}
	c.Root = true
	r, err := call(c)
	return r, true, err
}

// Cancel cancels one job, or every job on a printer.
func Cancel(job, printer string, all bool) (map[string]any, error) {
	var c Cmd
	switch {
	case all:
		if printer == "" {
			return nil, fmt.Errorf("all needs printer: cancelling every job on every printer is not offered")
		}
		if err := checkPrinter(printer); err != nil {
			return nil, err
		}
		c = Cmd{Name: "cancel", Args: []string{"-a", printer}}
	case job != "":
		if !jobID.MatchString(job) {
			return nil, fmt.Errorf("%q is not a job id", job)
		}
		c = Cmd{Name: "cancel", Args: []string{job}}
	default:
		return nil, fmt.Errorf("give job, or printer with all")
	}
	_, escalated, err := asAccountThenRoot(c)
	if err != nil {
		return nil, err
	}
	return map[string]any{"cancelled": strings.Join(c.Args, " "), "as_root": escalated}, nil
}

var requestID = regexp.MustCompile(`request id is (\S+)`)

// statFile tells a regular file. Tests replace it.
var statFile = func(p string) error {
	info, err := os.Stat(p)
	if err != nil {
		return err
	}
	if !info.Mode().IsRegular() {
		return fmt.Errorf("%s is not a regular file", p)
	}
	return nil
}

// Print sends a file to a printer.
func Print(file, printer string, copies int, opts map[string]string, title string) (map[string]any, error) {
	if !filepath.IsAbs(file) {
		return nil, fmt.Errorf("file must be an absolute path, not %q", file)
	}
	if err := statFile(file); err != nil {
		return nil, fmt.Errorf("cannot print %s: %v", file, err)
	}
	args := []string{}
	if printer != "" {
		if err := checkPrinter(printer); err != nil {
			return nil, err
		}
		args = append(args, "-d", printer)
	}
	args = append(args, "-n", strconv.Itoa(copies))
	names := make([]string, 0, len(opts))
	for k := range opts {
		names = append(names, k)
	}
	sort.Strings(names)
	for _, k := range names {
		args = append(args, "-o", k+"="+opts[k])
	}
	if title == "" {
		title = filepath.Base(file)
	}
	args = append(args, "-t", title, "--", file)
	r, err := call(Cmd{Name: "lp", Args: args})
	if err != nil {
		if strings.Contains(r.Stderr, "No default destination") {
			return nil, fmt.Errorf("no printer given and this machine has no default printer: name one, or set one with cups_default")
		}
		return nil, err
	}
	m := requestID.FindStringSubmatch(r.Stdout)
	if m == nil {
		return nil, fmt.Errorf("lp answered no job id: %s", strings.TrimSpace(r.Stdout+r.Stderr))
	}
	return map[string]any{"job": m[1], "file": file, "copies": copies, "follow": "cups_queue"}, nil
}

// Default answers the default printer, or sets it.
func Default(printer string) (map[string]any, error) {
	if printer == "" {
		d, err := defaultPrinter()
		if err != nil {
			return nil, err
		}
		return map[string]any{"default": d}, nil
	}
	if err := checkPrinter(printer); err != nil {
		return nil, err
	}
	was, err := defaultPrinter()
	if err != nil {
		return nil, err
	}
	if _, err := call(Cmd{Name: "lpadmin", Args: []string{"-d", printer}, Root: true}); err != nil {
		return nil, err
	}
	return map[string]any{"default": printer, "was": was}, nil
}

// Resume enables a printer and makes it accept jobs.
func Resume(printer string) (map[string]any, error) {
	if err := checkPrinter(printer); err != nil {
		return nil, err
	}
	for _, c := range []string{"cupsenable", "cupsaccept"} {
		if _, err := call(Cmd{Name: c, Args: []string{printer}, Root: true}); err != nil {
			return nil, err
		}
	}
	return map[string]any{"printer": printer, "enabled": true, "accepting": true}, nil
}

// DriverPackage is a package that brings filters or backends.
type DriverPackage struct {
	Package string `json:"package"`
	Version string `json:"version"`
	Foreign bool   `json:"foreign"`
}

// Model is one driver model CUPS offers.
type Model struct {
	PPD         string `json:"ppd"`
	Description string `json:"description"`
}

// QueueDriver is how one queue prints.
type QueueDriver struct {
	Printer    string `json:"printer"`
	MakeModel  string `json:"make_and_model"`
	Driverless bool   `json:"driverless"`
	URI        string `json:"uri"`
}

// DriversAnswer is what cups_drivers answers.
type DriversAnswer struct {
	Queues   []QueueDriver   `json:"queues"`
	Packages []DriverPackage `json:"driver_packages"`
	Models   []Model         `json:"models"`
	Matched  int             `json:"models_matched"`
	Findings []string        `json:"findings"`
}

// driverDirs are where drivers put what CUPS runs.
var driverDirs = []string{"/usr/lib/cups/filter", "/usr/lib/cups/backend"}

// basePackages bring CUPS's own filters and backends, not a printer's driver.
var basePackages = map[string]bool{"cups": true, "cups-filters": true, "libcups": true, "ghostscript": true, "cups-pdf": false}

// Drivers answers how each queue prints and which packages bring drivers.
func Drivers(match string, limit int) (DriversAnswer, error) {
	out := DriversAnswer{Queues: []QueueDriver{}, Packages: []DriverPackage{}, Models: []Model{}, Findings: []string{}}
	ps, err := Printers()
	if err != nil {
		return out, err
	}
	for _, p := range ps.Printers {
		out.Queues = append(out.Queues, QueueDriver{Printer: p.Name, MakeModel: p.MakeModel, Driverless: p.Driverless, URI: p.URI})
	}
	r := run(Cmd{Name: "pacman", Args: append([]string{"-Qo"}, driverDirs...)})
	if r.Error != "" {
		return out, failure(Cmd{Name: "pacman", Args: []string{"-Qo"}}, r)
	}
	seen := map[string]bool{}
	for _, l := range lines(r.Stdout) {
		if _, after, ok := strings.Cut(l, " is owned by "); ok {
			f := strings.Fields(after)
			if len(f) >= 2 && !seen[f[0]] && !basePackages[f[0]] {
				seen[f[0]] = true
				out.Packages = append(out.Packages, DriverPackage{Package: f[0], Version: f[1]})
			}
		}
	}
	if len(out.Packages) > 0 {
		r := run(Cmd{Name: "pacman", Args: []string{"-Qqm"}})
		foreign := map[string]bool{}
		for _, l := range lines(r.Stdout) {
			foreign[strings.TrimSpace(l)] = true
		}
		for i := range out.Packages {
			out.Packages[i].Foreign = foreign[out.Packages[i].Package]
		}
	}
	sort.Slice(out.Packages, func(i, k int) bool { return out.Packages[i].Package < out.Packages[k].Package })
	m, err := call(Cmd{Name: "lpinfo", Args: []string{"-m"}})
	if err != nil {
		return out, err
	}
	for _, l := range lines(m.Stdout) {
		ppd, desc, _ := strings.Cut(l, " ")
		if match != "" && !strings.Contains(strings.ToLower(desc), strings.ToLower(match)) && !strings.Contains(strings.ToLower(ppd), strings.ToLower(match)) {
			continue
		}
		out.Matched++
		if len(out.Models) < limit {
			out.Models = append(out.Models, Model{PPD: ppd, Description: desc})
		}
	}
	// Which driver packages no queue prints through.
	allDriverless := len(out.Queues) > 0
	for _, q := range out.Queues {
		allDriverless = allDriverless && q.Driverless
	}
	for _, p := range out.Packages {
		if p.Foreign {
			out.Findings = append(out.Findings, "driver package "+p.Package+" is not from the official repositories")
		}
		if allDriverless {
			out.Findings = append(out.Findings, "every queue prints driverless, so no queue uses the driver package "+p.Package)
		}
	}
	return out, nil
}