// Command owned judges how the catalogue's directories and archives treat files they did not write (novox/hq
// ADR 0422 §8, issue 1024). It refuses, naming the module, the resource and the reason:
//
//  1. a directory or archive without `unknown`, or with a value but move-out, module or program;
//
//  2. `move-out` on a path not under ${machine:account-home} or ${machine:agent-home};
//
//  3. `knows` with an empty, absolute, `.`/`..`/empty-component or repeated path;
//
//  4. a path one module declares (a resource's path, or a fact with "home": true) lying inside a directory of
//     another module, after ${dir:<id>} is resolved within each module and both homes are read as one root.
//     Archives are not containers for this rule. This holds for ~/.ssh what checks/sshdir held (ADR 0415 §6).
//
//  5. a directory that is, lies inside or holds a directory a system package owns under /var/lib, or any other
//     resource inside one (issue 1841: pacman's state directory, placed with "place": ".", was /var/lib/pacman, the
//     package manager's own database directory). A placed directory is resolved as the mesh resolves it with the
//     default data root: "." is /var/lib/<module>, "mesh" /var/lib/mesh/<module>, neither /var/lib/<module>/<id>.
//     The system directories are checks/owned/system, captured from a machine (pacman -Qo, /usr/lib/tmpfiles.d);
//     checks/owned/system-known names the exceptions still to fix, by module, resource and issue. That list only
//     shrinks: an entry that no longer collides is refused, and with -base one the trunk's copy does not hold.
//
//     go run . [-base <trunk's system-known>] <catalogue root>
//
// Exits 1 on a finding.
package main

import (
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
)

// The lists of rule 5, relative to the catalogue's root.
const (
	SystemList  = "checks/owned/system"
	SystemKnown = "checks/owned/system-known"
)

// Home is the one root both machine homes are read as.
const Home = "${home}"

var (
	ofDir   = regexp.MustCompile(`\$\{dir:([a-z0-9][a-z0-9_-]*)\}`)
	homeVar = strings.NewReplacer("${machine:account-home}", Home, "${machine:agent-home}", Home)
	values  = map[string]bool{"move-out": true, "module": true, "program": true}
)

// Finding is one refusal.
type Finding struct {
	Rule            int
	Module, ID, Why string
}

type resource struct {
	ID, Type, Path, Unknown, Place string
	Knows                          []string
	HasKnows                       bool
}

type parsed struct {
	Module    string
	Resources []resource
	Facts     []string // paths of facts with "home": true, under the home
}

func load(file string) (*parsed, error) {
	raw, err := os.ReadFile(file)
	if err != nil {
		return nil, err
	}
	var m struct {
		Module    string `json:"module"`
		Resources []struct {
			ID      string   `json:"id"`
			Type    string   `json:"type"`
			Path    string   `json:"path"`
			Place   string   `json:"place"`
			Unknown *string  `json:"unknown"`
			Knows   []string `json:"knows"`
		} `json:"resources"`
		Facts map[string]struct {
			Path string `json:"path"`
			Home bool   `json:"home"`
		} `json:"facts"`
	}
	if err := json.Unmarshal(raw, &m); err != nil {
		return nil, fmt.Errorf("%s: %w", file, err)
	}
	out := &parsed{Module: m.Module}
	if out.Module == "" {
		out.Module = filepath.Base(filepath.Dir(file))
	}
	for _, r := range m.Resources {
		x := resource{ID: r.ID, Type: r.Type, Path: r.Path, Place: r.Place, Knows: r.Knows, HasKnows: r.Knows != nil}
		if r.Unknown != nil {
			x.Unknown = *r.Unknown
			if x.Unknown == "" {
				x.Unknown = "(empty)"
			}
		}
		out.Resources = append(out.Resources, x)
	}
	keys := make([]string, 0, len(m.Facts))
	for k := range m.Facts {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	for _, k := range keys {
		if f := m.Facts[k]; f.Home && f.Path != "" {
			out.Facts = append(out.Facts, f.Path)
		}
	}
	return out, nil
}

// norm resolves ${dir:<id>} from the module's own resources, reads both homes as one root and cleans the path.
func norm(p string, dirs map[string]string) string {
	for i := 0; i < 8 && ofDir.MatchString(p); i++ {
		p = ofDir.ReplaceAllStringFunc(p, func(w string) string {
			if to, ok := dirs[ofDir.FindStringSubmatch(w)[1]]; ok {
				return to
			}
			return w
		})
	}
	p = homeVar.Replace(p)
	if p == "" {
		return ""
	}
	return path.Clean(p)
}

func underHome(p string) bool { return strings.HasPrefix(p, Home+"/") }

// badKnows says why a knows entry is refused, or "".
func badKnows(k string) string {
	if k == "" {
		return "is empty"
	}
	if strings.HasPrefix(k, "/") {
		return "is absolute"
	}
	for _, c := range strings.Split(strings.TrimSuffix(k, "/"), "/") {
		if c == "" || c == "." || c == ".." {
			return "has an empty, . or .. component"
		}
	}
	return ""
}

type declared struct {
	module, id, path string
}

// Check reads every manifest under root/modules and answers what it refuses.
func Check(root string, base []string) ([]Finding, error) {
	files, err := filepath.Glob(filepath.Join(root, "modules", "*", "module.json"))
	if err != nil {
		return nil, err
	}
	sort.Strings(files)
	system, err := readSystem(filepath.Join(root, SystemList))
	if err != nil {
		return nil, err
	}
	known, err := readLines(filepath.Join(root, SystemKnown))
	if err != nil && !errors.Is(err, os.ErrNotExist) {
		return nil, err
	}
	var out []Finding
	var paths []declared
	collided := map[string]bool{}
	type container struct{ module, path string }
	var containers []container
	for _, file := range files {
		m, err := load(file)
		if err != nil {
			return nil, err
		}
		dirs := map[string]string{}
		for _, r := range m.Resources {
			switch {
			case r.ID != "" && r.Path != "":
				dirs[r.ID] = r.Path
			case r.ID != "" && r.Type == "directory":
				// A directory the mesh places for the module (`place`): where it lies is the node-engine's, but it is
				// the module's own, so a path under it belongs to this module and to no other's directory of the same
				// id (issue 1484: two runs-as modules each keep a .ssh in their own state directory).
				dirs[r.ID] = "/placed/" + m.Module + "/" + r.ID
			}
		}
		out = append(out, inSystem(m, system, known, collided)...)
		for _, r := range m.Resources {
			p := norm(r.Path, dirs)
			if p != "" {
				paths = append(paths, declared{m.Module, r.ID, p})
			}
			if r.Type != "directory" && r.Type != "archive" {
				continue
			}
			if r.Type == "directory" && p != "" {
				containers = append(containers, container{m.Module, p})
			}
			add := func(rule int, why string) { out = append(out, Finding{rule, m.Module, r.ID, why}) }
			switch {
			case r.Unknown == "":
				add(1, "a "+r.Type+" without `unknown` (move-out, module or program)")
			case !values[r.Unknown]:
				add(1, fmt.Sprintf("`unknown` is %q, not move-out, module or program", r.Unknown))
			case r.Unknown == "move-out" && !underHome(p):
				add(2, fmt.Sprintf("`move-out` on %q, which is not under ${machine:account-home} or ${machine:agent-home}", r.Path))
			}
			seen := map[string]bool{}
			for _, k := range r.Knows {
				if why := badKnows(k); why != "" {
					add(3, fmt.Sprintf("`knows` entry %q %s", k, why))
					continue
				}
				c := strings.TrimSuffix(k, "/")
				if seen[c] {
					add(3, fmt.Sprintf("`knows` entry %q is repeated", k))
				}
				seen[c] = true
			}
			if r.HasKnows && len(r.Knows) == 0 {
				add(3, "`knows` is empty")
			}
		}
		for _, f := range m.Facts {
			if p := norm(Home+"/"+f, nil); p != "" {
				paths = append(paths, declared{m.Module, "fact " + f, p})
			}
		}
	}
	for _, k := range known {
		if !collided[k] {
			module, id, _ := strings.Cut(k, " ")
			id, _, _ = strings.Cut(id, " ")
			out = append(out, Finding{5, module, id, fmt.Sprintf("is listed in %s, and no longer lies in a system "+
				"package's directory: take the line out, so the list only shrinks", SystemKnown)})
		}
	}
	if base != nil {
		held := map[string]bool{}
		for _, b := range base {
			held[b] = true
		}
		for _, k := range known {
			if !held[k] {
				module, id, _ := strings.Cut(k, " ")
				id, _, _ = strings.Cut(id, " ")
				out = append(out, Finding{5, module, id, fmt.Sprintf("is a new line in %s, which the trunk's copy "+
					"does not hold: a module's directory is placed outside a system package's, never listed", SystemKnown)})
			}
		}
	}
	for _, d := range paths {
		for _, c := range containers {
			if c.module != d.module && (d.path == c.path || strings.HasPrefix(d.path, c.path+"/")) {
				out = append(out, Finding{4, d.module, d.id, fmt.Sprintf("declares %q, inside a directory of %s (%q)", d.path, c.module, c.path)})
			}
		}
	}
	return out, nil
}

// systemDir is one directory a system package owns, and what says so.
type systemDir struct{ Path, Source string }

// readLines is a list's lines, without comments and blank lines.
func readLines(file string) ([]string, error) {
	raw, err := os.ReadFile(file)
	if err != nil {
		return nil, err
	}
	var lines []string
	for _, line := range strings.Split(string(raw), "\n") {
		if line = strings.TrimSpace(line); line != "" && !strings.HasPrefix(line, "#") {
			lines = append(lines, line)
		}
	}
	return lines, nil
}

// readSystem is the list of system directories: "<absolute path> <package>: <how it was read>" per line. Absent or
// empty, the check fails: a list that says nothing would let every module through.
func readSystem(file string) ([]systemDir, error) {
	lines, err := readLines(file)
	if err != nil {
		return nil, fmt.Errorf("rule 5 reads the system packages' directories from %s: %w", file, err)
	}
	if len(lines) == 0 {
		return nil, fmt.Errorf("%s names no system package's directory, so rule 5 would pass everything", file)
	}
	var out []systemDir
	for _, line := range lines {
		p, source, _ := strings.Cut(line, " ")
		if !strings.HasPrefix(p, "/var/lib/") || strings.TrimSpace(source) == "" {
			return nil, fmt.Errorf("%s: %q is not \"/var/lib/<directory> <package>: <how it was read>\"", file, line)
		}
		out = append(out, systemDir{path.Clean(p), strings.TrimSpace(source)})
	}
	return out, nil
}

// placedAt is where the mesh places a pathless directory with the default data root (mesh-sdk catalogue dirsFor).
func placedAt(module string, r resource) string {
	switch r.Place {
	case ".":
		return "/var/lib/" + module
	case "mesh":
		return "/var/lib/mesh/" + module
	}
	return "/var/lib/" + module + "/" + r.ID
}

// inSystem is rule 5 for one module: each resource whose resolved path collides with a system package's directory,
// unless system-known lists it (then it is marked collided, so a stale line is found).
func inSystem(m *parsed, system []systemDir, known []string, collided map[string]bool) []Finding {
	real := map[string]string{}
	for _, r := range m.Resources {
		if r.Type == "directory" && r.Path == "" && r.ID != "" {
			real[r.ID] = placedAt(m.Module, r)
		}
	}
	for _, r := range m.Resources {
		if r.ID != "" && r.Path != "" {
			real[r.ID] = r.Path
		}
	}
	var out []Finding
	for _, r := range m.Resources {
		p := ""
		if r.Path != "" {
			p = norm(r.Path, real)
		} else if r.Type == "directory" {
			p = real[r.ID]
		}
		if !strings.HasPrefix(p, "/") {
			continue
		}
		for _, s := range system {
			inside := p == s.Path || strings.HasPrefix(p, s.Path+"/")
			holds := r.Type == "directory" && strings.HasPrefix(s.Path, p+"/")
			if !inside && !holds {
				continue
			}
			listed := ""
			for _, k := range known {
				if strings.HasPrefix(k, m.Module+" "+r.ID+" ") || k == m.Module+" "+r.ID {
					listed = k
				}
			}
			if listed != "" {
				collided[listed] = true
				break
			}
			how := "is or lies inside"
			if holds {
				how = "holds"
			}
			out = append(out, Finding{5, m.Module, r.ID, fmt.Sprintf("resolves to %q, which %s %s, the directory of the "+
				"system package %s; place it under /var/lib/mesh/%s (\"place\": \"mesh\") or a path of its own", p, how,
				s.Path, s.Source, m.Module)})
			break
		}
	}
	return out
}

func main() {
	baseFile := flag.String("base", "", "the trunk's copy of "+SystemKnown+": a line it does not hold is refused")
	flag.Parse()
	root := "."
	if flag.NArg() > 0 {
		root = flag.Arg(0)
	}
	var base []string
	if *baseFile != "" {
		lines, err := readLines(*baseFile)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			os.Exit(1)
		}
		base = append([]string{}, lines...)
	}
	found, err := Check(root, base)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	for _, f := range found {
		cite := "novox/hq ADR 0422 §8, issue 1024"
		if f.Rule == 5 {
			cite = "issue 1841"
		}
		fmt.Printf("%s: %s: %s (rule %d, %s)\n", f.Module, f.ID, f.Why, f.Rule, cite)
	}
	if len(found) > 0 {
		os.Exit(1)
	}
	fmt.Println("owned paths: every directory and archive says how it treats unknown files; no module declares inside another's directory, or in a system package's")
}