// Package config holds the two files kettle reads: what this project is, and
// who this machine is.
//
// The split is the whole design. `<project>/.kettle/config.yaml` says which
// tracker repository the issues belong to and which login to reach it under —
// facts about the project, written by `kettle init`. The credentials themselves
// live in one file per machine, outside any repository, mode 0600.
//
// A token in a file inside a working tree ends up in a commit. Not always, not
// immediately, and not by anyone careless — but a project config is exactly the
// file somebody eventually decides to share, and a secret that has ever been
// pushed is a secret that has to be rotated. So the project pins a login by
// NAME and the name is worth nothing on its own.
package config

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

	"gopkg.in/yaml.v3"

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

// Environment overrides, each winning over the file it shadows. They exist for
// CI, for a one-off run against another instance, and for anyone who would
// rather not have a token on disk at all.
const (
	EnvLogin = "KETTLE_LOGIN"
	EnvURL   = "KETTLE_URL"
	EnvToken = "KETTLE_TOKEN"
	EnvRepo  = "KETTLE_REPO"
	// EnvHome relocates the machine-wide login file; the test suite sets it so
	// a run can never read or write the developer's own.
	EnvHome = "KETTLE_CONFIG_HOME"
)

const projectHeader = `# kettle — project configuration
#
# login  the name of a login in the machine-wide file, NOT a credential.
#        Manage those with ` + "`kettle auth`" + `; they live outside this tree.
# repo   the tracker repository these issues belong to, as owner/name.
#
# Overrides, when you need one: ` + EnvLogin + `, ` + EnvRepo + `, ` + EnvURL + `, ` + EnvToken + `.
`

// Project is `<project>/.kettle/config.yaml`.
type Project struct {
	// Login names an entry in the machine-wide login file. Never a token.
	Login string `yaml:"login"`
	// Repo is the tracker repository, as owner/name.
	Repo string `yaml:"repo"`
}

// Login is one set of credentials for one Gitea instance.
type Login struct {
	Name  string `yaml:"name"`
	URL   string `yaml:"url"`
	User  string `yaml:"user,omitempty"`
	Token string `yaml:"token"`
}

// Logins is the machine-wide file.
type Logins struct {
	Logins []Login `yaml:"logins"`
}

// ErrNoConfig means the project has no config.yaml yet.
var ErrNoConfig = errors.New("no project configuration")

// ProjectPath is where this project's config.yaml is, or "" with no project.
func ProjectPath(start string) string { return project.ConfigPath(start) }

// LoadProject reads the project configuration.
//
// A missing file is ErrNoConfig, not an empty config: "this project has not
// been told which tracker it belongs to" and "it belongs to no tracker" are
// different answers and only one of them is fixable by running init.
func LoadProject(start string) (*Project, error) {
	path := ProjectPath(start)
	if path == "" {
		return nil, project.NotFoundError(start)
	}
	raw, err := os.ReadFile(path)
	if os.IsNotExist(err) {
		return nil, fmt.Errorf("%w at %s — run `kettle init` there", ErrNoConfig, path)
	}
	if err != nil {
		return nil, err
	}
	var p Project
	if err := strictUnmarshal(raw, &p); err != nil {
		return nil, fmt.Errorf("%s: %w", path, err)
	}
	return &p, nil
}

// ReadProjectFile reads a config.yaml at a path already known, reporting
// whether the file was there.
//
// LoadProject resolves the path by walking for a marker, which is the right
// thing everywhere except inside `kettle init` — the command that is creating
// the marker, and on a dry run may not have created it at all.
func ReadProjectFile(path string) (*Project, bool, error) {
	raw, err := os.ReadFile(path)
	if os.IsNotExist(err) {
		return &Project{}, false, nil
	}
	if err != nil {
		return nil, false, err
	}
	var p Project
	if err := strictUnmarshal(raw, &p); err != nil {
		return nil, true, fmt.Errorf("%s: %w", path, err)
	}
	return &p, true, nil
}

// SaveProject writes the project configuration, header comment and all.
func SaveProject(path string, p *Project) error {
	body, err := yaml.Marshal(p)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return err
	}
	return os.WriteFile(path, append([]byte(projectHeader+"\n"), body...), 0o644)
}

// LoginsPath is the machine-wide login file.
//
// One file per machine, deliberately outside every working tree: which tokens
// this computer holds is a fact about the computer, the way which issues a tree
// holds is a fact about the tree.
func LoginsPath() string {
	if h := os.Getenv(EnvHome); h != "" {
		return filepath.Join(h, "logins.yaml")
	}
	if x := os.Getenv("XDG_CONFIG_HOME"); x != "" {
		return filepath.Join(x, "kettle", "logins.yaml")
	}
	home, err := os.UserHomeDir()
	if err != nil {
		return ""
	}
	return filepath.Join(home, ".config", "kettle", "logins.yaml")
}

// LoadLogins reads the machine-wide login file. A missing file is an empty
// list, not an error: a machine with no logins yet is an ordinary machine.
func LoadLogins() (*Logins, error) {
	path := LoginsPath()
	if path == "" {
		return &Logins{}, nil
	}
	raw, err := os.ReadFile(path)
	if os.IsNotExist(err) {
		return &Logins{}, nil
	}
	if err != nil {
		return nil, err
	}
	var l Logins
	if err := strictUnmarshal(raw, &l); err != nil {
		return nil, fmt.Errorf("%s: %w", path, err)
	}
	return &l, nil
}

// SaveLogins writes the machine-wide login file with 0600, and creates its
// directory with 0700. The file holds bearer tokens; nothing else on the
// machine has any business reading it.
func SaveLogins(l *Logins) error {
	path := LoginsPath()
	if path == "" {
		return errors.New("cannot locate a home directory for the login file — set " + EnvHome)
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
		return err
	}
	body, err := yaml.Marshal(l)
	if err != nil {
		return err
	}
	return os.WriteFile(path, body, 0o600)
}

// Find returns the login with this name.
func (l *Logins) Find(name string) *Login {
	for i := range l.Logins {
		if l.Logins[i].Name == name {
			return &l.Logins[i]
		}
	}
	return nil
}

// Names lists every login on this machine, for an error message that can
// actually be acted on.
func (l *Logins) Names() []string {
	out := make([]string, 0, len(l.Logins))
	for _, e := range l.Logins {
		out = append(out, e.Name)
	}
	return out
}

// Resolved is everything the transport needs, with every override applied.
type Resolved struct {
	Login string
	URL   string
	Token string
	Owner string
	Repo  string
}

// Slug is owner/name, the way a tracker writes it.
func (r *Resolved) Slug() string { return r.Owner + "/" + r.Repo }

// Redacted is the same thing with the token replaced, for printing.
func (r *Resolved) Redacted() Resolved {
	out := *r
	if out.Token != "" {
		out.Token = "(set)"
	}
	return out
}

// Resolve merges the project config, the machine's login file, and the
// environment into what the transport needs.
//
// Every failure names the file it read and the command that fixes it. "401
// Unauthorized" is what happens when this function is allowed to return a
// half-filled struct.
func Resolve(start string) (*Resolved, error) {
	var p Project
	if loaded, err := LoadProject(start); err == nil {
		p = *loaded
	} else if !errors.Is(err, ErrNoConfig) {
		return nil, err
	}

	out := &Resolved{Login: p.Login}
	if v := os.Getenv(EnvLogin); v != "" {
		out.Login = v
	}

	repo := p.Repo
	if v := os.Getenv(EnvRepo); v != "" {
		repo = v
	}
	if repo != "" {
		owner, name, ok := strings.Cut(repo, "/")
		if !ok || owner == "" || name == "" {
			return nil, fmt.Errorf("repo %q is not owner/name", repo)
		}
		out.Owner, out.Repo = owner, name
	}

	if out.Login != "" {
		logins, err := LoadLogins()
		if err != nil {
			return nil, err
		}
		entry := logins.Find(out.Login)
		if entry == nil {
			known := "none on this machine"
			if names := logins.Names(); len(names) > 0 {
				known = strings.Join(names, ", ")
			}
			return nil, fmt.Errorf("no login %q in %s — known: %s; add one with `kettle auth add`",
				out.Login, LoginsPath(), known)
		}
		out.URL, out.Token = entry.URL, entry.Token
	}

	if v := os.Getenv(EnvURL); v != "" {
		out.URL = v
	}
	if v := os.Getenv(EnvToken); v != "" {
		out.Token = v
	}
	out.URL = strings.TrimRight(out.URL, "/")
	return out, nil
}

// Require is Resolve plus the assertion that the result can actually reach a
// tracker.
func Require(start string) (*Resolved, error) {
	r, err := Resolve(start)
	if err != nil {
		return nil, err
	}
	var missing []string
	if r.URL == "" {
		missing = append(missing, "a URL (pin a login with `kettle init --login`, or set "+EnvURL+")")
	}
	if r.Token == "" {
		missing = append(missing, "a token (`kettle auth add`, or set "+EnvToken+")")
	}
	if r.Owner == "" {
		missing = append(missing, "a repository (`kettle init --repo owner/name`, or set "+EnvRepo+")")
	}
	if len(missing) > 0 {
		return nil, fmt.Errorf("this project has no %s", strings.Join(missing, ", and no "))
	}
	return r, nil
}

// strictUnmarshal refuses keys the struct does not know.
//
// The alternative is silence: an older binary reading a newer config would drop
// the setting it did not recognize, and rewriting the file would delete it.
// Being told "unknown field" beats finding out later.
func strictUnmarshal(raw []byte, out any) error {
	dec := yaml.NewDecoder(strings.NewReader(string(raw)))
	dec.KnownFields(true)
	if err := dec.Decode(out); err != nil && err.Error() != "EOF" {
		return err
	}
	return nil
}