// mesh-compose is mesh-sdk's composer command (novox/hq ADR 0482 clause 4, issue 1621): it reads a composer.Request on
// standard input, validates every manifest with this mesh-sdk's reader, composes the machines named in each case and
// writes one composer.Verdict on standard output. Built at any commit of mesh-sdk (or at the mesh-sdk a module pins),
// it answers what that commit's composition answers, so a program that links one mesh-sdk can have another's judged.
//
//	mesh-compose < request.json > verdict.json
//	mesh-compose -request request.json > verdict.json
//	mesh-compose -catalogue <dir> [-node <name>]... [-depth resolve|compose] [-declarations] [< request.json]
//
// -catalogue reads <dir>/modules/*/module.json and a module.json at <dir>'s root as the first case's manifests (a
// checkout or `git archive` of the catalogue repository at a ref: the command fetches nothing). -node adds a machine to
// compose; -declarations answers each machine's declared paths with their owners and modes.
//
// It opens no network connection, bus, store or file beyond its standard input, the -request file and the -catalogue
// directory, and reads
// no environment. Exit codes: 0 the verdict is written (a machine that does not compose is a verdict, not an error);
// 1 the request cannot be read or run, said on standard error; 2 the flags are wrong.
package main

import (
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"git.novox.be/novox/mesh-sdk/go/catalogue"
	"git.novox.be/novox/mesh-sdk/go/composer"
)

func main() {
	os.Exit(run(os.Args[1:], os.Stdin, os.Stdout, os.Stderr))
}

type nodes []string

func (n *nodes) String() string     { return strings.Join(*n, ",") }
func (n *nodes) Set(v string) error { *n = append(*n, v); return nil }

// run is the command: its arguments, standard input, output and error; it answers the exit code.
func run(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
	fs := flag.NewFlagSet("mesh-compose", flag.ContinueOnError)
	fs.SetOutput(stderr)
	catalogueDir := fs.String("catalogue", "", "a catalogue checkout: <dir>/modules/*/module.json are the first case's manifests")
	var machines nodes
	fs.Var(&machines, "node", "a machine to compose (repeatable)")
	depth := fs.String("depth", "", "resolve or compose (default: the request's, else compose)")
	declarations := fs.Bool("declarations", false, "answer each composed machine's declared paths, owners and modes")
	requestFile := fs.String("request", "", "read the request from this file instead of standard input (a run step that hands no standard input)")
	if err := fs.Parse(args); err != nil {
		return 2
	}
	if fs.NArg() > 0 {
		fmt.Fprintf(stderr, "mesh-compose: unexpected arguments %q\n", fs.Args())
		return 2
	}
	var raw []byte
	var err error
	if *requestFile != "" {
		raw, err = os.ReadFile(*requestFile)
	} else {
		raw, err = io.ReadAll(stdin)
	}
	if err != nil {
		fmt.Fprintln(stderr, "mesh-compose: the request cannot be read:", err)
		return 1
	}
	var req composer.Request
	if strings.TrimSpace(string(raw)) == "" {
		if *catalogueDir == "" {
			fmt.Fprintln(stderr, "mesh-compose: no request on standard input and no -catalogue")
			return 1
		}
		req = composer.Request{V: composer.Version}
	} else if req, err = composer.Decode(raw); err != nil {
		fmt.Fprintln(stderr, "mesh-compose:", err)
		return 1
	}
	if *catalogueDir != "" {
		read, err := readCatalogue(*catalogueDir)
		if err != nil {
			fmt.Fprintln(stderr, "mesh-compose:", err)
			return 1
		}
		if len(req.Cases) == 0 {
			req.Cases = []composer.Case{{Name: "catalogue", Manifests: map[string]composer.Manifest{}}}
		}
		if req.Cases[0].Manifests == nil {
			req.Cases[0].Manifests = map[string]composer.Manifest{}
		}
		for name, m := range read {
			if _, given := req.Cases[0].Manifests[name]; !given {
				req.Cases[0].Manifests[name] = m
			}
		}
		// The catalogue's list of predefined keys is the one its manifests' fallbacks are judged against (ADR 0348 §7).
		if req.Predefined == nil {
			list, err := catalogue.ReadPredefined(*catalogueDir)
			if err != nil {
				fmt.Fprintln(stderr, "mesh-compose:", err)
				return 1
			}
			req.Predefined = list
		}
	}
	req.Machines = append(req.Machines, machines...)
	if *depth != "" {
		req.Depth = *depth
	}
	if *declarations {
		req.Declarations = true
	}
	v, err := composer.Run(req)
	if err != nil {
		fmt.Fprintln(stderr, "mesh-compose:", err)
		return 1
	}
	enc := json.NewEncoder(stdout)
	if err := enc.Encode(v); err != nil {
		fmt.Fprintln(stderr, "mesh-compose: the verdict cannot be written:", err)
		return 1
	}
	return 0
}

// readCatalogue reads every module.json of a catalogue checkout by its module's name: the root's and each of
// modules/*/. A manifest whose name cannot be read is kept under its directory's name, so the reader's refusal is said.
func readCatalogue(dir string) (map[string]composer.Manifest, error) {
	paths, err := filepath.Glob(filepath.Join(dir, "modules", "*", "module.json"))
	if err != nil {
		return nil, err
	}
	if _, err := os.Stat(filepath.Join(dir, "module.json")); err == nil {
		paths = append(paths, filepath.Join(dir, "module.json"))
	}
	if len(paths) == 0 {
		return nil, fmt.Errorf("the catalogue %s holds no module.json", dir)
	}
	sort.Strings(paths)
	out := map[string]composer.Manifest{}
	for _, p := range paths {
		raw, err := os.ReadFile(p)
		if err != nil {
			return nil, err
		}
		var probe struct {
			Module string `json:"module"`
		}
		name := filepath.Base(filepath.Dir(p))
		if json.Unmarshal(raw, &probe) == nil && probe.Module != "" {
			name = probe.Module
		}
		if _, twice := out[name]; twice {
			return nil, errors.New("the catalogue " + dir + " defines " + name + " twice")
		}
		out[name] = composer.Manifest{Raw: raw}
	}
	return out, nil
}