// Command paths holds the catalogue's modules to talking over the bus (novox/hq ADR 0260): no module
// names a path under /run or /var/lib that another module's manifest places. Such a path is that
// module's state on its machine, and a second module reading or writing it is two modules talking
// through a file, which the bus exists to replace.
//
// A module owns every `path` of its resources under /run/ or /var/lib/. Every other module's manifest
// and every file of its own except its documentation and its tests is searched for each, as a whole
// path: followed by nothing, a slash, or a character no path takes.
//
//	go run . <catalogue root>
//
// Exits 1 on a finding.
package main

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

// stateRoots are where a machine keeps a module's state.
var stateRoots = []string{"/run/", "/var/lib/"}

type manifest struct {
	Module    string           `json:"module"`
	Resources []map[string]any `json:"resources"`
}

// Finding is one module naming another's path.
type Finding struct {
	Module, File, Path, Owner string
}

func (f Finding) String() string {
	return fmt.Sprintf("%s names %s in %s, and the path is %s's; modules talk over the bus (novox/hq ADR 0260)",
		f.Module, f.Path, f.File, f.Owner)
}

// Check is every finding in the catalogue at root.
func Check(root string) ([]Finding, error) {
	dirs, err := filepath.Glob(filepath.Join(root, "modules", "*", "module.json"))
	if err != nil {
		return nil, err
	}
	owner := map[string]string{}
	modules := map[string]string{}
	for _, f := range dirs {
		raw, err := os.ReadFile(f)
		if err != nil {
			return nil, err
		}
		var m manifest
		if err := json.Unmarshal(raw, &m); err != nil {
			return nil, fmt.Errorf("%s: %w", f, err)
		}
		modules[m.Module] = filepath.Dir(f)
		for _, r := range m.Resources {
			p, _ := r["path"].(string)
			for _, root := range stateRoots {
				if strings.HasPrefix(p, root) && len(p) > len(root) {
					owner[strings.TrimRight(p, "/")] = m.Module
				}
			}
		}
	}
	paths := make([]string, 0, len(owner))
	for p := range owner {
		paths = append(paths, p)
	}
	sort.Strings(paths)
	patterns := map[string]*regexp.Regexp{}
	for _, p := range paths {
		patterns[p] = regexp.MustCompile(regexp.QuoteMeta(p) + `(?:$|[^A-Za-z0-9._-])`)
	}
	var out []Finding
	names := make([]string, 0, len(modules))
	for n := range modules {
		names = append(names, n)
	}
	sort.Strings(names)
	for _, module := range names {
		dir := modules[module]
		err := filepath.WalkDir(dir, func(path string, d fs.DirEntry, err error) error {
			if err != nil || d.IsDir() {
				return err
			}
			name := d.Name()
			if strings.HasSuffix(name, ".md") || strings.HasSuffix(name, "_test.go") ||
				name == "go.sum" || name == "package-lock.json" {
				return nil
			}
			raw, err := os.ReadFile(path)
			if err != nil {
				return err
			}
			text := string(raw)
			for _, p := range paths {
				if owner[p] != module && patterns[p].MatchString(text) {
					rel, _ := filepath.Rel(root, path)
					out = append(out, Finding{Module: module, File: rel, Path: p, Owner: owner[p]})
				}
			}
			return nil
		})
		if err != nil {
			return nil, err
		}
	}
	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(2)
	}
	for _, f := range found {
		fmt.Println(f)
	}
	if len(found) > 0 {
		os.Exit(1)
	}
	fmt.Println("paths: no module names another's state on its machine")
}