package cmd

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"

	"edge-infra.dev/pkg/lib/cli/rags"
	"edge-infra.dev/pkg/lib/cli/sink"
	"edge-infra.dev/pkg/tools/dlog"
)

// TODO: automatically increment based on last dlog (eg 0004 is biggest is 0003)
// TODO: allow setting more pieces of frontmatter on create

func newCreateCmd() *sink.Command {
	var (
		dir, template string
		tags          []string
	)

	cmd := &sink.Command{
		Use:   "create [flags] <file>",
		Short: "Create decision logs from a template.",
		Flags: []*rags.Rag{
			dirFlag(&dir),
			templateFlag(&template),
			{
				Name:  "tags",
				Usage: "Comma separated list of tags to apply to new dlog. Can be provided multiple times",
				Value: &rags.StringSet{Var: &tags},
			},
		},
		Exec: func(_ context.Context, r sink.Run) error {
			if len(r.Args()) != 1 {
				return fmt.Errorf("a name for the decision log file is required")
			}

			p := filepath.Join(dir, r.Args()[0])
			_, err := os.Stat(p)
			if err == nil {
				return fmt.Errorf("%s already exists", p)
			}

			t, err := os.Open(template)
			if err != nil {
				return fmt.Errorf("failed to open template %s: %w", template, err)
			}

			return createDLog(p, t, time.Now(), tags)
		},
	}

	return cmd
}

func createDLog(path string, t *os.File, d time.Time, tags []string) error {
	buf := new(bytes.Buffer)
	scanner := bufio.NewScanner(t)
	for scanner.Scan() {
		text := scanner.Text()
		// Cheat here by updating the frontmatter in string form to avoid
		// encoding roundtrip and losing comments in the template describing
		// frontmatter elements
		if strings.HasPrefix(text, "date:") {
			buf.WriteString(fmt.Sprintf("date: %s", dlog.Time{Time: d}))
			buf.WriteString("\n")
			continue
		}
		if len(tags) > 0 && strings.HasPrefix(text, "tags:") {
			buf.WriteString(fmt.Sprintf(
				"tags: [%s]",
				// Rebuild string for consistent spacing
				strings.Join(tags, ", ")),
			)
			buf.WriteString("\n")
			continue
		}

		buf.WriteString(text)
		buf.WriteString("\n")
	}
	if scanner.Err() != nil {
		return fmt.Errorf("failed to read template %s: %w", t.Name(), scanner.Err())
	}

	f, err := os.Create(path)
	if err != nil {
		return fmt.Errorf("failed to create %s: %w", path, err)
	}
	if _, err := buf.WriteTo(f); err != nil {
		return fmt.Errorf("failed to write %s: %w", path, err)
	}
	return nil
}