// Command ingest puts Markdown documents into a tenant's knowledge corpus.
//
// The knowledge layer had an Ingester and no way to reach it — everything that
// had ever been ingested was ingested by a test. This is the missing half.
//
//	make ingest ORG=<slug>
//
// Each document declares its own audience in front matter, and a document that
// declares none is REFUSED rather than defaulted. Both directions of a default
// are wrong and neither raises: tenant-wide over-shares something somebody
// meant to restrict, and empty indexes it into invisibility. See §5.
package main

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/jackc/pgx/v5"

	"github.com/krow/krow-backend/go-api/internal/config"
	"github.com/krow/krow-backend/go-api/internal/db"
	"github.com/krow/krow-backend/go-api/internal/domain"
	"github.com/krow/krow-backend/go-api/internal/knowledge"
	"github.com/krow/krow-backend/go-api/internal/runtime"
)

func main() {
	var (
		dir     = flag.String("dir", "./knowledge", "directory of Markdown documents")
		org     = flag.String("org", "", "organization slug to ingest into (required)")
		dryRun  = flag.Bool("dry-run", false, "parse and report, write nothing")
		timeout = flag.Duration("timeout", 15*time.Minute, "overall timeout")
	)
	flag.Parse()

	if err := run(*dir, *org, *dryRun, *timeout); err != nil {
		fmt.Fprintf(os.Stderr, "ingest: %v\n", err)
		os.Exit(1)
	}
}

// parsed is one document, read and validated before anything is opened.
type parsed struct {
	file string
	doc  knowledge.Document
}

func run(dir, orgSlug string, dryRun bool, timeout time.Duration) error {
	if strings.TrimSpace(orgSlug) == "" {
		return errors.New("an organization is required: --org=<slug>")
	}

	docs, err := readAll(dir)
	if err != nil {
		return err
	}
	if len(docs) == 0 {
		return fmt.Errorf("no documents found in %s", dir)
	}

	for _, d := range docs {
		tags, err := knowledge.TagsFor(d.doc.Audience)
		if err != nil {
			return fmt.Errorf("%s: %w", d.file, err)
		}
		fmt.Printf("  %-28s %-14s %s\n", d.doc.ExternalID, d.doc.Source, strings.Join(tags, " "))
	}
	if dryRun {
		fmt.Printf("\n%d document(s) parsed; nothing written (--dry-run)\n", len(docs))
		return nil
	}

	cfg, err := config.Load()
	if err != nil {
		return fmt.Errorf("load configuration: %w", err)
	}

	embedder := runtime.NewEmbedder(*cfg)
	if embedder == nil {
		// Not fatal. Chunks are written and left unembedded for `make reembed`,
		// so a corpus is keyword-searchable immediately and dense-searchable
		// once a model exists. Said out loud because a silently keyword-only
		// corpus is a retrieval problem that surfaces months later as "the
		// agent seems worse than it was".
		fmt.Println("\nno embedding model configured — documents will be keyword-searchable only")
		fmt.Println("set EMBED_PROVIDER and run `make reembed` to finish them")
	} else {
		fmt.Printf("\nembedding with %s\n", embedder.Model())
	}

	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	database, err := db.Open(ctx, cfg.DB)
	if err != nil {
		return fmt.Errorf("connect: %w", err)
	}
	defer database.Close()

	var orgID string
	err = database.Pool.QueryRow(ctx,
		`SELECT id::text FROM organizations WHERE slug = $1`, orgSlug).Scan(&orgID)
	if errors.Is(err, pgx.ErrNoRows) {
		return fmt.Errorf("no organization with slug %q", orgSlug)
	}
	if err != nil {
		return fmt.Errorf("resolve organization: %w", err)
	}

	ing := knowledge.NewIngester(database.Pool, embedder)
	var chunks, unchanged int
	for _, d := range docs {
		res, err := ing.Ingest(ctx, orgID, d.doc)
		if err != nil {
			return fmt.Errorf("%s: %w", d.file, err)
		}
		chunks += res.Chunks
		if res.Unchanged {
			unchanged++
			fmt.Printf("  %-28s unchanged (%d chunks)\n", d.doc.ExternalID, res.Chunks)
			continue
		}
		note := ""
		if res.EmbeddingDeferred {
			note = "  [not embedded]"
		}
		fmt.Printf("  %-28s %d chunks%s\n", d.doc.ExternalID, res.Chunks, note)
	}

	fmt.Printf("\n%d document(s), %d chunk(s), %d unchanged, into %s\n",
		len(docs), chunks, unchanged, orgSlug)
	return nil
}

/* ── Reading the directory ──────────────────────────────────────────────── */

func readAll(dir string) ([]parsed, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil, fmt.Errorf("read %s: %w", dir, err)
	}

	var out []parsed
	for _, e := range entries {
		name := e.Name()
		if e.IsDir() || !strings.HasSuffix(name, ".md") || name == "README.md" {
			continue
		}
		raw, err := os.ReadFile(filepath.Join(dir, name))
		if err != nil {
			return nil, fmt.Errorf("read %s: %w", name, err)
		}
		doc, err := parse(name, string(raw))
		if err != nil {
			return nil, fmt.Errorf("%s: %w", name, err)
		}
		out = append(out, parsed{file: name, doc: *doc})
	}
	sort.Slice(out, func(a, b int) bool { return out[a].file < out[b].file })
	return out, nil
}

// parse reads a document's front matter and body.
//
// A small reader rather than a YAML library: the front matter here is four flat
// keys, and the value of a real parser is handling shapes this format does not
// have. What matters is that a malformed audience is an error rather than a
// silent default.
func parse(file, raw string) (*knowledge.Document, error) {
	body := strings.ReplaceAll(raw, "\r\n", "\n")
	if !strings.HasPrefix(body, "---\n") {
		return nil, errors.New("no front matter; a document must declare its source and audience")
	}
	end := strings.Index(body[4:], "\n---")
	if end < 0 {
		return nil, errors.New("front matter is not closed")
	}
	head := body[4 : 4+end]
	rest := strings.TrimLeft(body[4+end+4:], "\n")

	fields := map[string]string{}
	for _, line := range strings.Split(head, "\n") {
		k, v, ok := strings.Cut(line, ":")
		if !ok {
			continue
		}
		fields[strings.TrimSpace(k)] = strings.TrimSpace(v)
	}

	source := fields["source"]
	if source == "" {
		return nil, errors.New("no `source`; an agent's spec names the corpora it may read")
	}

	audience, err := parseAudience(fields["audience"])
	if err != nil {
		return nil, err
	}

	// The filename is the external id, so re-ingesting the same file updates
	// rather than duplicating. Stable, obvious, and something a person can
	// point at.
	id := strings.TrimSuffix(file, ".md")

	title := fields["title"]
	if title == "" {
		title = id
	}

	return &knowledge.Document{
		Source: source, ExternalID: id, Title: title,
		URI: fields["uri"], Body: rest, Audience: audience,
	}, nil
}

// parseAudience turns the declared audience into the one the ingester takes.
//
// An empty or unrecognised value is an ERROR. That is the whole point: §5
// refuses a document that reaches nobody, and a typo'd role silently producing
// a tag no principal holds is the same failure wearing better clothes.
func parseAudience(raw string) (knowledge.Audience, error) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return knowledge.Audience{}, errors.New(
			"no `audience`; a document that declares none is unreachable, not private")
	}

	var a knowledge.Audience
	for _, part := range strings.Split(raw, ",") {
		part = strings.TrimSpace(part)
		switch {
		case part == "tenant":
			a.Tenant = true
		case strings.HasPrefix(part, "role:"):
			name := strings.TrimPrefix(part, "role:")
			role, ok := domain.ParseRole(name)
			if !ok {
				return knowledge.Audience{}, fmt.Errorf(
					"%q is not a role; use admin, employer or talent", name)
			}
			a.Roles = append(a.Roles, role)
		case strings.HasPrefix(part, "email:"):
			a.Emails = append(a.Emails, strings.TrimPrefix(part, "email:"))
		default:
			return knowledge.Audience{}, fmt.Errorf(
				"%q is not an audience; use tenant, role:<name> or email:<address>", part)
		}
	}
	return a, nil
}