package cli

import (
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"git.vakhrushev.me/av/convy/internal/manifest"
	"git.vakhrushev.me/av/convy/internal/project"
)

// convy sync makes the files agree with the manifest. The manifest is the
// truth: it says which components exist, where they write and what each takes,
// and everything under those directories follows from that.
//
// It divides from pull by what it is about. pull is about the contents of a
// copy — it takes the text of every subscription afresh, and the diff it leaves
// is the point of running it. sync is about the set of files: what the manifest
// calls for and is not there gets assembled, what is there and nothing calls
// for gets reported and, when nothing of the repository is in it, removed.
//
// A copy carrying a local part is never removed. Below the marker is the one
// thing in the directory that exists nowhere else, and a command that tidies up
// has no business deciding it is spent.

func runSync(env Env, args []string) ExitCode {
	fs := flag.NewFlagSet("convy sync", flag.ContinueOnError)
	fs.SetOutput(env.Err)
	root := fs.String("root", "", "root of the project; it is looked up upwards by default")
	forComponent := fs.String("for", "", "component to bring in line; every one of them by default")
	dry := fs.Bool("dry-run", false, "say what would change and change nothing")
	if err := fs.Parse(args); err != nil {
		return Usage
	}
	if code := noStrayArgs(env, "convy sync", fs.Args()); code != OK {
		return code
	}

	o, code := openProject(env, *root)
	if code != OK {
		return code
	}
	defer o.Close()

	names, code := components(env, o.Manifest, *forComponent)
	if code != OK {
		return code
	}

	problems := validateManifest(o, names)
	for _, p := range problems {
		fmt.Fprintf(env.Err, "%s\n", p)
	}
	if len(problems) > 0 {
		fmt.Fprintln(env.Err, "\nthe manifest is what the layout follows, so nothing was touched")
		return Failed
	}

	changed, left := 0, 0
	for i, name := range names {
		c := o.Manifest.Components[name]
		if i > 0 {
			fmt.Fprintln(env.Out)
		}
		fmt.Fprintf(env.Out, "%s → %s\n", name, c.Dir)
		n, stuck, code := syncComponent(env, o, c, *dry)
		if code != OK {
			return code
		}
		changed += n
		left += stuck
	}

	fmt.Fprintln(env.Out)
	switch {
	case *dry && changed > 0:
		fmt.Fprintf(env.Out, "%s would change; run without --dry-run to do it\n", plural(changed, "file"))
	case changed > 0:
		fmt.Fprintf(env.Out, "%s changed; convy pull takes the text of the rest afresh\n", plural(changed, "file"))
	case left == 0:
		fmt.Fprintln(env.Out, "the layout already follows the manifest")
	}
	if left > 0 {
		fmt.Fprintf(env.Out, "%s left alone: nothing subscribes to it and it holds a local part\n", plural(left, "file"))
		return Failed
	}
	return OK
}

// validate checks the manifest against itself and against the suite. Everything
// wrong is reported at once: being sent back one line at a time is the worst way
// to learn what a file wants.
func validateManifest(o *opened, names []string) []string {
	var out []string
	if err := distinctDirs(o.Manifest); err != nil {
		out = append(out, err.Error())
	}
	for _, name := range names {
		c := o.Manifest.Components[name]
		if c.Dir == "" {
			out = append(out, fmt.Sprintf("the component %q names no dir, and a copy has to be written somewhere", name))
		}
		if len(c.Lang) > 1 {
			out = append(out, fmt.Sprintf("the component %q declares two languages (%s): a line of code is written in one of them, and a component is the region where every chosen layer holds at once — split it",
				name, strings.Join(c.Lang, ", ")))
		}
		seen := make(map[string]bool, len(c.Topics))
		for _, topic := range c.Topics {
			switch {
			case seen[topic]:
				out = append(out, fmt.Sprintf("the component %q takes %q twice", name, topic))
			case o.Suite.Manifest.TopicRetired(topic):
				out = append(out, fmt.Sprintf("the component %q takes %q, which the suite has retired: %s",
					name, topic, o.Suite.Manifest.Topics.Retired[topic]))
			case !o.Suite.Manifest.TopicLive(topic):
				out = append(out, fmt.Sprintf("the component %q takes %q, and the suite declares no such topic", name, topic))
			default:
				if taken, _ := o.Suite.Assemble(topic, project.Axis(c)); len(taken) == 0 {
					out = append(out, fmt.Sprintf("the component %q takes %q, and no layer of it fits this component", name, topic))
				}
			}
			seen[topic] = true
		}
	}
	return out
}

// syncComponent brings one directory in line. It returns how many files moved
// and how many it would not touch.
func syncComponent(env Env, o *opened, c manifest.Component, dry bool) (changed, left int, code ExitCode) {

	for _, topic := range c.Topics {
		rel := filepath.ToSlash(filepath.Join(c.Dir, topic+".md"))
		if exists(filepath.Join(o.Root, filepath.FromSlash(rel))) {
			continue
		}
		changed++
		if dry {
			fmt.Fprintf(env.Out, "  + %-28s subscribed, and no file\n", rel)
			continue
		}
		made, err := project.Assemble(o.Suite, o.Root, c, topic)
		if err != nil {
			fmt.Fprintf(env.Err, "  %s: %s\n", topic, err)
			return changed, left, Failed
		}
		fmt.Fprintf(env.Out, "  + %-28s %s\n", made.Path, plural(len(made.Layers), "layer"))
	}

	orphans, err := orphaned(o.Root, c)
	if err != nil {
		fmt.Fprintln(env.Err, err)
		return changed, left, Failed
	}
	for _, orphan := range orphans {
		switch {
		case orphan.local:
			left++
			fmt.Fprintf(env.Out, "  ! %-28s nothing subscribes to %q, and it carries a local part: remove it by hand or subscribe again\n",
				orphan.path, orphan.topic)
		case dry:
			changed++
			fmt.Fprintf(env.Out, "  - %-28s nothing subscribes to %q\n", orphan.path, orphan.topic)
		default:
			if err := os.Remove(filepath.Join(o.Root, filepath.FromSlash(orphan.path))); err != nil {
				fmt.Fprintln(env.Err, err)
				return changed, left, Failed
			}
			changed++
			fmt.Fprintf(env.Out, "  - %-28s nothing subscribes to %q\n", orphan.path, orphan.topic)
		}
	}

	if !dry {
		guide, err := project.Reading(o.LangRoot, o.Suite.Manifest.Language.Reading, o.Root, c.Dir)
		if err != nil {
			fmt.Fprintf(env.Err, "  %s\n", err)
			return changed, left, Failed
		}
		fmt.Fprintf(env.Out, "  = %-28s the guide to reading a rule\n", guide)
	}
	return changed, left, OK
}

// orphan is a copy in a component directory that the manifest does not call for.
type orphan struct {
	path  string
	topic string
	local bool
}

// orphaned finds the copies nothing subscribes to. What is a copy is decided by
// the origin key: README.md belongs to the repository, READING.md belongs to the
// suite, and a file whose origin was taken away has become a document of the
// repository — none of the three is anyone's to remove.
func orphaned(root string, c manifest.Component) ([]orphan, error) {
	docs, broken := copies(root, c.Dir)
	if len(broken) > 0 {
		return nil, broken[0]
	}
	var out []orphan
	for _, d := range docs {
		if c.Subscribed(d.Front.Origin) {
			continue
		}
		local := ""
		if at := d.Marker(); at > 0 {
			local = strings.TrimSpace(strings.TrimPrefix(strings.TrimSpace(d.Below(at)), project.LocalMarker))
		}
		out = append(out, orphan{path: d.Path, topic: d.Front.Origin, local: local != ""})
	}
	return out, nil
}