// 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).
//
//     go run . <catalogue root>
//
// Exits 1 on a finding.
package main

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

// 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 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"`
			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, 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) ([]Finding, error) {
	files, err := filepath.Glob(filepath.Join(root, "modules", "*", "module.json"))
	if err != nil {
		return nil, err
	}
	sort.Strings(files)
	var out []Finding
	var paths []declared
	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 {
			if r.ID != "" && r.Path != "" {
				dirs[r.ID] = r.Path
			}
		}
		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 _, 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
}

func main() {
	root := "."
	if len(os.Args) > 1 {
		root = os.Args[1]
	}
	found, err := Check(root)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	for _, f := range found {
		fmt.Printf("%s: %s: %s (rule %d, novox/hq ADR 0422 §8, issue 1024)\n", f.Module, f.ID, f.Why, f.Rule)
	}
	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")
}