package issue

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"git.noodles.cam/claude-skills/marketplace/cli/internal/project"
)

// The store holds two kinds of file, and only one of them is a store.
//
// An issue whose origin is Local lives here and nowhere else — that file IS the
// issue, and losing it loses the work. Anything with a tracker origin is a
// cache: the tracker has it, this copy is a working copy, and it is deleted the
// moment a push confirms the tracker is up to date.

// Root resolves the issue store for the current project. An explicit out
// overrides it and is used exactly as typed: a relative out stays relative to
// the working directory, because that is what the operator asked for.
func Root(out string) string {
	if out != "" {
		return out
	}
	return project.StoreRoot("")
}

// ErrStoreMissing marks the "the store directory is not there" failure.
//
// Deliberately a different answer from "the store is empty". One is a path that
// does not exist, the other is a repository with no issues filed yet, and
// conflating the two is exactly what made a missed directory look like an empty
// backlog.
var ErrStoreMissing = errors.New("store missing")

// StoreExists reports whether root is a directory that can be read as a store.
func StoreExists(root string) bool {
	if root == "" {
		return false
	}
	fi, err := os.Stat(root)
	return err == nil && fi.IsDir()
}

// RequireStore asserts the store is there before reading or writing it.
//
// An empty root means no project was found at all — a different failure from a
// project whose store has not been created yet, and the message says so.
func RequireStore(root string) error {
	if root == "" {
		return fmt.Errorf("%w: %s", ErrStoreMissing, project.NotFoundError(""))
	}
	if !StoreExists(root) {
		return fmt.Errorf("%w: store %s does not exist", ErrStoreMissing, root)
	}
	return nil
}

// CreateStore creates the store, reporting whether it made the directory.
//
// Only the commands that legitimately bootstrap a store call this — `new` and
// `pull` — and both announce it. Nothing creates a store as a side effect of a
// write: a missing directory is something to report, not something to conjure.
// An unresolved root is never conjured either — without a marker there is no
// project to create a store IN, and guessing one is how a store once ended up
// inside the plugin.
func CreateStore(root string) (bool, error) {
	if root == "" {
		return false, fmt.Errorf("%w: %s", ErrStoreMissing, project.NotFoundError(""))
	}
	if StoreExists(root) {
		return false, nil
	}
	if err := os.MkdirAll(root, 0o755); err != nil {
		return false, err
	}
	return true, nil
}

// StoreError says why root cannot be read as a store, or nil when it holds
// issues.
//
// The three messages are distinct on purpose — no project at all, a project
// with no store, and a store with nothing in it are three different things to
// do next.
func StoreError(root string) error {
	switch {
	case root == "":
		return project.NotFoundError("")
	case !StoreExists(root):
		return fmt.Errorf("store %s does not exist — nothing was created; pass --out to point elsewhere", root)
	case len(AllIDs(root)) == 0:
		return fmt.Errorf("store %s exists but is empty", root)
	}
	return nil
}

// PathOf is where the issue with this id lives.
func PathOf(root, id string) string { return filepath.Join(root, id+".md") }

// AllIDs lists every issue in the store, by slug.
//
// An issue file is named by its slug and a slug has no dot in it, so
// `<id>.comments.md` — the thread the sync layer parks beside an issue — is not
// one, and neither is anything else that grew a second extension. Without that
// rule `wire-sqlc.comments` reads as an issue called `wire-sqlc.comments`, and
// a bare push tries to file the comment thread as a unit of work.
func AllIDs(root string) []string {
	if !StoreExists(root) {
		return nil
	}
	entries, err := os.ReadDir(root)
	if err != nil {
		return nil
	}
	var out []string
	for _, e := range entries {
		name := e.Name()
		if !strings.HasSuffix(name, ".md") {
			continue
		}
		if strings.HasPrefix(name, ".") || strings.HasPrefix(name, "INDEX") ||
			strings.HasPrefix(name, "tree-") {
			continue
		}
		id := name[:len(name)-3]
		if strings.Contains(id, ".") {
			continue
		}
		out = append(out, id)
	}
	sort.Strings(out)
	return out
}

// SlugFiles lists every file the store holds under one slug — the issue and its
// sidecars.
//
// `<id>.md` is the issue. Anything named `<id>.<something>` beside it is a
// companion another layer parked there (`<id>.comments.md` is the one that
// exists today). AllIDs already refuses to read those as issues because a slug
// has no dot in it; this is the same rule read the other way round.
//
// Which is how the domain can remove an issue completely without learning what
// any of those companions are: it does not need to know that a comment thread
// exists to know that a file named after this issue belongs to it and goes when
// it goes. The issue's own file comes first — it is the headline of any receipt
// printed from this list.
//
// A missing store is an empty list, not an error: nothing is there to remove.
func SlugFiles(root, id string) []string {
	entries, err := os.ReadDir(root)
	if err != nil {
		return nil
	}
	prefix, own := id+".", id+".md"
	var self, sidecars []string
	for _, e := range entries {
		name := e.Name()
		if !strings.HasPrefix(name, prefix) || e.IsDir() {
			continue
		}
		p := filepath.Join(root, name)
		if name == own {
			self = append(self, p)
		} else {
			sidecars = append(sidecars, p)
		}
	}
	sort.Strings(sidecars)
	return append(self, sidecars...)
}

// Load reads one issue. The file name wins over the id in the metadata block.
func Load(root, id string) (*Issue, error) {
	raw, err := os.ReadFile(PathOf(root, id))
	if err != nil {
		return nil, err
	}
	return FromText(string(raw), id), nil
}

// LoadAll reads the whole store.
func LoadAll(root string) (map[string]*Issue, error) {
	out := map[string]*Issue{}
	for _, id := range AllIDs(root) {
		i, err := Load(root, id)
		if err != nil {
			return nil, err
		}
		out[id] = i
	}
	return out, nil
}

// Save writes an issue to the store, which must already exist.
func Save(root string, i *Issue) (string, error) {
	if err := RequireStore(root); err != nil {
		return "", err
	}
	p := PathOf(root, i.ID)
	if err := os.WriteFile(p, []byte(i.Text()), 0o644); err != nil {
		return "", err
	}
	return p, nil
}