package buildstep

// **Regenerate and compare** (CAT-BG5, CAT-BN2; novox/hq ADR 0608 §5, design 26 *Contracts modules*). A module whose
// package artifact names `generated-from` holds contracts only: every file under its generated roots is written by the
// seat generator (package seatgen beside this file, command cmd/seatgen) from the definitions in that directory. A build module regenerates them with the generator
// it was built with (its version is this package's requirement, so a new generator is a new build module and a new
// fingerprint of what it builds) and names each file out of step: one that differs, one missing, one under a generated
// root the generator did not write. The test step fails on any; a trunk build's ask answers them in its out-of-step
// (sdkstep.BuildAnswer.OutOfStep), so the builder's build end raises generated-types-out-of-step even where no test
// step runs. Each build module compares its own roots: mesh-build-go `go`, mesh-build-node `ts`.

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

	"git.novox.be/novox/mesh-catalog/modules/mesh-build-go/buildstep/seatgen"
	"git.novox.be/novox/mesh-sdk/go/catalogue"
)

// GeneratedRootGo and GeneratedRootTS are the generated roots of a contracts module, one per build module.
const (
	GeneratedRootGo = "go"
	GeneratedRootTS = "ts"
)

var goModuleLine = regexp.MustCompile(`(?m)^module\s+(\S+)`)

// OutOfStep is every file under root, a path from the module's directory, that the generator writes otherwise than the
// module holds it, for each `generated-from` its package artifacts name, sorted and each once; none for a module naming
// none. The generated trees' names are read from the seats already generated in <from> (generatedNames).
func OutOfStep(moduleDir, root string) ([]string, error) {
	raw, err := os.ReadFile(filepath.Join(moduleDir, "module.json"))
	if errors.Is(err, os.ErrNotExist) {
		return nil, nil // no manifest here: nothing names generated-from
	}
	if err != nil {
		return nil, fmt.Errorf("the module's manifest cannot be read for its generated files: %w", err)
	}
	var m catalogue.Manifest
	if err := json.Unmarshal(raw, &m); err != nil {
		return nil, fmt.Errorf("the module's manifest does not parse: %w", err)
	}
	froms := map[string]bool{}
	if m.Build != nil {
		for _, a := range m.Build.Artifacts {
			if a.GeneratedFrom != "" {
				froms[filepath.Clean(a.GeneratedFrom)] = true
			}
		}
	}
	seen := map[string]bool{}
	for from := range froms {
		if filepath.IsAbs(from) || from == ".." || strings.HasPrefix(from, "../") {
			return nil, fmt.Errorf("generated-from %q is not inside the module", from)
		}
		dir := filepath.Join(moduleDir, from)
		goModule, tsPackage, err := generatedNames(dir)
		if err != nil {
			return nil, err
		}
		g, err := seatgen.Load(dir, goModule, tsPackage)
		if err != nil {
			return nil, fmt.Errorf("the seat definitions in %s do not load: %w", from, err)
		}
		files, err := seatgen.Generate(g)
		if err != nil {
			return nil, fmt.Errorf("the seat definitions in %s do not generate: %w", from, err)
		}
		out, err := seatgen.Compare(dir, files)
		if err != nil {
			return nil, err
		}
		for _, line := range out {
			p, _, _ := strings.Cut(line, ": ")
			if p == root || strings.HasPrefix(p, root+"/") {
				seen[filepath.ToSlash(filepath.Join(from, p))] = true
			}
		}
	}
	paths := make([]string, 0, len(seen))
	for p := range seen {
		paths = append(paths, p)
	}
	sort.Strings(paths)
	return paths, nil
}

// generatedNames reads the names the generated trees are rooted at from the seats already generated in dir: a seat's Go
// module is `<root>/seats/<seat without hyphens>` and its npm package `<root>-<seat>` (a contracts module has no root
// package of either kind, ADR 0635 §1). A module with no seat generated yet gives none, and the generator says so only
// if a seat is defined whole.
func generatedNames(dir string) (goModule, tsPackage string, err error) {
	names, _ := filepath.Glob(filepath.Join(dir, "seats", "*", "seat.json"))
	for _, p := range names {
		seat := filepath.Base(filepath.Dir(p))
		pkg := strings.ReplaceAll(seat, "-", "")
		if goModule == "" {
			if raw, err := os.ReadFile(filepath.Join(dir, GeneratedRootGo, "seats", pkg, "go.mod")); err == nil {
				if m := goModuleLine.FindSubmatch(raw); m != nil {
					goModule = strings.TrimSuffix(string(m[1]), "/seats/"+pkg)
				}
			}
		}
		if tsPackage == "" {
			if raw, err := os.ReadFile(filepath.Join(dir, GeneratedRootTS, "seats", pkg, "package.json")); err == nil {
				var p struct {
					Name string `json:"name"`
				}
				if json.Unmarshal(raw, &p) == nil {
					tsPackage = strings.TrimSuffix(p.Name, "-"+seat)
				}
			}
		}
	}
	return goModule, tsPackage, nil
}

// ModuleDirs is every directory in tree that holds a module.json, in any folder (ADR 0634 §8: a module is found by its
// manifest, whether it lies at the root, under modules/ or in a folder of another module), the tree's own first, then
// sorted. Hidden directories, node_modules and testdata are not entered.
func ModuleDirs(tree string) ([]string, error) {
	var out []string
	err := filepath.WalkDir(tree, func(p string, e os.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if e.IsDir() {
			if n := e.Name(); p != tree && (strings.HasPrefix(n, ".") || n == "node_modules" || n == "testdata") {
				return filepath.SkipDir
			}
			return nil
		}
		if e.Name() == "module.json" {
			out = append(out, filepath.Dir(p))
		}
		return nil
	})
	sort.Strings(out)
	return out, err
}

// CompareStep is AskSteps.Compare for a build module comparing root: it reads {"workspace", "module"}, the workspace's
// tree where tree says it is (the build module's own layout), and answers {"out-of-step": [...]}.
func CompareStep(root string, tree func(workspace string) string) StepFunc {
	return func(_ context.Context, args map[string]any) (any, error) {
		ws, _ := args["workspace"].(string)
		mod, _ := args["module"].(string)
		if ws == "" {
			return nil, Refuse("the compare names no workspace")
		}
		paths, err := OutOfStep(filepath.Join(tree(ws), filepath.FromSlash(mod)), root)
		if err != nil {
			return nil, err
		}
		return map[string]any{"out-of-step": paths}, nil
	}
}