// Package config reads the per-host settings loomctl needs to talk to a git host.
//
// The config is not only a secret. It is how you talk to a host at all — which
// is why it is a set of named contexts with one current, and why a host's URL
// shapes live here rather than in what a person types. Nobody should have to
// know that gitea serves raw files from /raw/branch/<branch>/ to adopt a
// document.
//
// It lives in the user's home directory and never in a repository.
package config

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"strings"
)

// Context is one named way of talking to one host.
type Context struct {
	Host string `json:"host"`
	// Flavor selects the URL shapes: gitea, github or gitlab. Empty means gitea.
	Flavor string `json:"flavor,omitempty"`
	// Token is read-only. loomctl never writes over the network, so a token it
	// is given should not carry write scope.
	Token string `json:"token,omitempty"`
}

type Config struct {
	CurrentContext string             `json:"current-context"`
	Contexts       map[string]Context `json:"contexts"`
}

// Path is where the config lives. Never inside a repository.
func Path() string {
	if p := os.Getenv("LOOMCTL_CONFIG"); p != "" {
		return p
	}
	home, err := os.UserHomeDir()
	if err != nil {
		return ""
	}
	return filepath.Join(home, ".config", "loomctl", "config.json")
}

// Load reads the config. A missing file is not an error: everything loomctl
// does against a public repository works with no credential and no context.
func Load() (*Config, error) {
	c := &Config{Contexts: map[string]Context{}}
	p := Path()
	if p == "" {
		return c, nil
	}
	b, err := os.ReadFile(p)
	if errors.Is(err, fs.ErrNotExist) {
		return c, nil
	}
	if err != nil {
		return nil, fmt.Errorf("reading %s: %w", p, err)
	}
	if err := json.Unmarshal(b, c); err != nil {
		return nil, fmt.Errorf("parsing %s: %w", p, err)
	}
	if c.Contexts == nil {
		c.Contexts = map[string]Context{}
	}
	return c, nil
}

// Current returns the context a bare `owner/repo` is resolved against.
func (c *Config) Current() (Context, error) {
	if c.CurrentContext == "" {
		return Context{}, fmt.Errorf("no current-context in %s — a bare owner/repo has no host to resolve against", Path())
	}
	ctx, ok := c.Contexts[c.CurrentContext]
	if !ok {
		return Context{}, fmt.Errorf("current-context %q is not defined in %s", c.CurrentContext, Path())
	}
	if ctx.Host == "" {
		return Context{}, fmt.Errorf("context %q has no host", c.CurrentContext)
	}
	return ctx, nil
}

// TokenFor returns the token for a host, or "" if we have none.
//
// An environment variable wins over the file, so a token can be supplied for
// one invocation without ever being written to disk.
func (c *Config) TokenFor(host string) string {
	if t := os.Getenv("LOOMCTL_TOKEN_" + envKey(host)); t != "" {
		return t
	}
	if t := os.Getenv("LOOMCTL_TOKEN"); t != "" {
		return t
	}
	for _, ctx := range c.Contexts {
		if ctx.Host == host && ctx.Token != "" {
			return ctx.Token
		}
	}
	return ""
}

func envKey(host string) string {
	r := strings.NewReplacer(".", "_", "-", "_", ":", "_")
	return strings.ToUpper(r.Replace(host))
}

// RawURL builds the address a document is served from, given owner/repo and a
// path inside the repository.
//
// For gitea the short form is deliberate: the host redirects it to the resolved
// branch, so the URL recorded in the lock names a branch rather than a moving
// ref, without anybody having to know which branch it was.
func (c Context) RawURL(ownerRepo, pathInRepo string) (string, bool) {
	switch c.flavor() {
	case "gitea":
		return fmt.Sprintf("https://%s/%s/raw/%s", c.Host, ownerRepo, pathInRepo), true
	case "github":
		return fmt.Sprintf("https://raw.githubusercontent.com/%s/%%s/%s", ownerRepo, pathInRepo), false
	case "gitlab":
		return fmt.Sprintf("https://%s/%s/-/raw/%%s/%s", c.Host, ownerRepo, pathInRepo), false
	}
	return "", false
}

// CloneURL is what git is pointed at.
func (c Context) CloneURL(ownerRepo string) string {
	return fmt.Sprintf("https://%s/%s.git", c.Host, ownerRepo)
}

func (c Context) flavor() string {
	if c.Flavor == "" {
		return "gitea"
	}
	return strings.ToLower(c.Flavor)
}

// Flavors names what RawURL understands, for error messages.
func Flavors() string { return "gitea, github, gitlab" }