// Command noplacement refuses what the repository path of placement left behind (novox/hq ADR 0567 §10, §12).
//
// Placement, which module runs on which node, is bus state held by the seat mesh-placement; no file of the
// catalogue says it, and no manifest reads it from the delivery indexer, which no longer keeps it. It refuses:
//
//  1. a `placement` directory (or file) at the root of the catalogue;
//
//  2. a `particulars` file at the root (the mesh's node names come from the checker's run, §16);
//
//  3. a manifest naming a state, stream, event or bucket of the indexer's placement (`mesh-delivery-indexer.placement…`
//     or `mesh-delivery-indexer_placement…`) in any string value, such as `reads`;
//
//  4. a manifest, other than mesh-controller's, that reads the controller's assignments (`mesh-controller.assignments`):
//     every reader takes placement from the seat mesh-placement (novox/hq ADR 0549 §3, ADR 0567), and the lease write is
//     refused while one still reads them (ADR 0549 §6; issue 774). The modules that still read them for what the
//     placement does not carry are named in checks/noplacement/assignments-readers, each with why; that list only
//     shrinks: an entry whose module no longer reads them is refused too.
//
//     go run . <catalogue root>
//
// Exits 1 on a finding.
package main

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

// Prefixes are the names of the indexer's placement parts; a manifest string starting with one names them.
var Prefixes = []string{"mesh-delivery-indexer.placement", "mesh-delivery-indexer_placement"}

// Findings is every refusal in the catalogue at root, sorted.
func Findings(root string) ([]string, error) {
	var out []string
	if _, err := os.Lstat(filepath.Join(root, "placement")); err == nil {
		out = append(out, "placement: the repository holds no placement; it is bus state of the seat mesh-placement (novox/hq ADR 0567 §10)")
	}
	if _, err := os.Lstat(filepath.Join(root, "particulars")); err == nil {
		out = append(out, "particulars: the repository lists no node names; the checker hands them to the check (novox/hq ADR 0567 §16)")
	}
	manifests, err := filepath.Glob(filepath.Join(root, "modules", "*", "module.json"))
	if err != nil {
		return nil, err
	}
	sort.Strings(manifests)
	for _, file := range manifests {
		raw, err := os.ReadFile(file)
		if err != nil {
			return nil, err
		}
		var doc any
		if err := json.Unmarshal(raw, &doc); err != nil {
			return nil, fmt.Errorf("%s: %w", file, err)
		}
		module := filepath.Base(filepath.Dir(file))
		for _, s := range named(doc, nil) {
			out = append(out, fmt.Sprintf("%s: names %q, which the indexer no longer keeps; placement is the seat mesh-placement's (novox/hq ADR 0567 §12)", module, s))
		}
	}
	readers, err := assignmentsReaders(root)
	if err != nil {
		return nil, err
	}
	out = append(out, readers...)
	sort.Strings(out)
	return out, nil
}

// AssignmentsRead is the controller's assignments as a manifest reads them, and Allowed the file, relative to the
// catalogue's root, that names the modules still reading them: `<module> <why>` per line, `#` a comment.
const (
	AssignmentsRead = "mesh-controller.assignments"
	Allowed         = "checks/noplacement/assignments-readers"
)

// assignmentsReaders is every finding on the reads of the controller's assignments: a module other than the controller
// reading them that Allowed does not name, and a module Allowed names that no longer reads them (issue 774).
func assignmentsReaders(root string) ([]string, error) {
	allowed := map[string]bool{}
	raw, err := os.ReadFile(filepath.Join(root, Allowed))
	if err != nil && !os.IsNotExist(err) {
		return nil, err
	}
	for _, line := range strings.Split(string(raw), "\n") {
		if f := strings.Fields(line); len(f) > 0 && !strings.HasPrefix(f[0], "#") {
			allowed[f[0]] = true
		}
	}
	manifests, err := filepath.Glob(filepath.Join(root, "modules", "*", "module.json"))
	if err != nil {
		return nil, err
	}
	var found []string
	reads := map[string]bool{}
	for _, path := range manifests {
		raw, err := os.ReadFile(path)
		if err != nil {
			return nil, err
		}
		var m struct {
			Module string   `json:"module"`
			Reads  []string `json:"reads"`
		}
		if json.Unmarshal(raw, &m) != nil || m.Module == "mesh-controller" {
			continue // a manifest that does not read is the manifest checks' to refuse
		}
		for _, r := range m.Reads {
			if strings.TrimSpace(r) != AssignmentsRead {
				continue
			}
			reads[m.Module] = true
			if !allowed[m.Module] {
				found = append(found, fmt.Sprintf("%s reads %s: read where modules run from mesh-delivery-assigner.placement, "+
					"the seat mesh-placement's (novox/hq ADR 0549 §3, ADR 0567); the lease write is refused while a module reads "+
					"the assignments (ADR 0549 §6)", m.Module, AssignmentsRead))
			}
		}
	}
	for module := range allowed {
		if !reads[module] {
			found = append(found, fmt.Sprintf("%s names %s, which no longer reads %s: take it off the list, which only shrinks",
				Allowed, module, AssignmentsRead))
		}
	}
	return found, nil
}

// named collects the strings of a decoded manifest that start with one of the Prefixes.
func named(v any, into []string) []string {
	switch v := v.(type) {
	case string:
		for _, p := range Prefixes {
			if strings.HasPrefix(v, p) {
				return append(into, v)
			}
		}
	case []any:
		for _, e := range v {
			into = named(e, into)
		}
	case map[string]any:
		for _, e := range v {
			into = named(e, into)
		}
	}
	return into
}

func main() {
	if len(os.Args) != 2 {
		fmt.Fprintln(os.Stderr, "usage: noplacement <catalogue root>")
		os.Exit(2)
	}
	found, err := Findings(os.Args[1])
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	for _, f := range found {
		fmt.Println(f)
	}
	if len(found) > 0 {
		os.Exit(1)
	}
	fmt.Println("no placement directory, no manifest reads the indexer's placement, and only the modules listed read the controller's assignments")
}