// Package controllerdeps is the catalogue's dependence check on the controller (novox/hq ADR 0590 §5, issue 1126): the
// controller is not placed, so no module of this tree reads, requires, invokes, consumes, waits on, uses or otherwise
// names it. Nothing is kept: not the lease, not the entries once kept to its write (ADR 0571 §13, superseded with ADR
// 0582). A later decision that places a controller again must first lift this check.
//
// It refuses, over the tree at root:
//
//   - a directory modules/mesh-controller: the controller is no module of the catalogue;
//   - a manifest string naming the controller's seat, a state, verb or event of it, or one of its buckets
//     (`mesh-controller.<name>`, `seat:mesh-controller.<verb>`, `mesh-controller_<bucket>`), anywhere in the manifest;
//   - a manifest string that is the bare module name `mesh-controller` outside the module's own `config`, where a value
//     is the module's data (an issue owner naming the controller's repository is no dependency), not an address;
//   - a line of any module's file naming one of the controller's buckets (`mesh-controller_`): its buckets are removed
//     after the controller's end (ADR 0590 §6), so a reader of one reads nothing. A test (`_test.go`, `.test.ts`) reads
//     no live bucket, its names are its own data, and a `testdata` directory is a copy of text from elsewhere (a design,
//     a backlog): both are skipped.
//
// The rule is said once, here, for the catalogue: decoding stays the manifests check's (a manifest that is no JSON is
// an error here, never judged).
package controllerdeps

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

// Module is the controller's module name, and Bucket the prefix every bucket of its carries.
const (
	Module = "mesh-controller"
	Bucket = Module + "_"
)

// address is a string naming the controller's seat, one of its states, verbs or events, or one of its buckets.
var address = regexp.MustCompile(`(^|[^A-Za-z0-9_-])(seat:)?mesh-controller([._][A-Za-z0-9])`)

// Refusals is each reason the check gives over the tree at root, sorted; none when it passes.
func Refusals(root string) ([]string, error) {
	var out []string
	if _, err := os.Lstat(filepath.Join(root, "modules", Module)); err == nil {
		out = append(out, Module+": the controller is no module of the catalogue: it is not placed and nothing may depend on it (novox/hq ADR 0590 §5)")
	}
	files, err := filepath.Glob(filepath.Join(root, "modules", "*", "module.json"))
	if err != nil {
		return nil, err
	}
	for _, f := range files {
		raw, err := os.ReadFile(f)
		if err != nil {
			return nil, err
		}
		var doc any
		if err := json.Unmarshal(raw, &doc); err != nil {
			return nil, fmt.Errorf("%s: %w", f, err)
		}
		module := filepath.Base(filepath.Dir(f))
		for _, s := range names(doc, false, nil) {
			out = append(out, fmt.Sprintf("%s: names %q: the controller is not placed, so no manifest reads, requires, invokes, "+
				"consumes, waits on or uses it; name the seat that holds the job now (novox/hq ADR 0590 §5)", module, s))
		}
	}
	buckets, err := bucketLines(root)
	if err != nil {
		return nil, err
	}
	out = append(out, buckets...)
	sort.Strings(out)
	return out, nil
}

// names collects the strings of a decoded manifest that name the controller; inConfig is under the module's `config`.
func names(v any, inConfig bool, into []string) []string {
	switch v := v.(type) {
	case string:
		if address.MatchString(v) || (!inConfig && strings.TrimSpace(v) == Module) {
			into = append(into, v)
		}
	case []any:
		for _, e := range v {
			into = names(e, inConfig, into)
		}
	case map[string]any:
		keys := make([]string, 0, len(v))
		for k := range v {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		for _, k := range keys {
			into = names(v[k], inConfig || k == "config", into)
		}
	}
	return into
}

// bucketLines is every line of a module's file, outside tests and testdata, that names one of the controller's buckets.
func bucketLines(root string) ([]string, error) {
	var out []string
	modules := filepath.Join(root, "modules")
	err := filepath.WalkDir(modules, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			if os.IsNotExist(err) && path == modules {
				return nil
			}
			return err
		}
		if d.IsDir() {
			if n := d.Name(); n == "testdata" || n == "node_modules" || n == ".git" {
				return filepath.SkipDir
			}
			return nil
		}
		if !d.Type().IsRegular() || strings.HasSuffix(d.Name(), "_test.go") || strings.HasSuffix(d.Name(), ".test.ts") {
			return nil
		}
		f, err := os.Open(path)
		if err != nil {
			return err
		}
		defer f.Close()
		sc := bufio.NewScanner(f)
		sc.Buffer(make([]byte, 0, 64*1024), 16*1024*1024)
		rel, _ := filepath.Rel(root, path)
		for n := 1; sc.Scan(); n++ {
			if strings.Contains(sc.Text(), Bucket) {
				out = append(out, fmt.Sprintf("%s:%d: names the controller's bucket (%s…): its buckets are removed after its "+
					"end (novox/hq ADR 0590 §6); read the seat that holds the job now", filepath.ToSlash(rel), n, Bucket))
			}
		}
		return sc.Err()
	})
	return out, err
}