package main

import (
	"bufio"
	"os"
	"path/filepath"
	"strings"
)

// Config holds all externally configurable settings. It is read entirely from
// ~/.mgshrc and then overlaid with MGSH_* environment variables — there are no
// built-in defaults. Missing required settings are a fatal error (see
// missingRequired).
type Config struct {
	Base        string // project base directory
	GitHost     string // git server host
	GitPort     string // ssh port
	GitUser     string // ssh user
	GitPath     string // remote path holding the bare repos
	GitKey      string // ssh key name (informational)
	GitName     string // git user.name to set globally ("" = leave alone)
	GitEmail    string // git user.email to set globally ("" = leave alone)
	PushDefault string // git push.default to set globally ("" = leave alone)
	Editor      string // editor/opener used as fallback by `open` ("" = coda)
	RemoteURL   string // public mirror server base URL (Gitea/GitHub/GitLab)
	RemoteKey   string // API token for the mirror server (used by `pushremote`)
	RemoteType  string // "gitea"|"github"|"gitlab" (auto-detected when empty)
	RemoteVis   string // visibility of created repos: "private" (default)|"public"
	Mirror      string // truthy -> `push` also mirrors via `pushremote`
}

// requiredKeys lists the settings mgsh cannot run without.
var requiredKeys = []string{"base", "githost", "gitport", "gituser", "gitpath"}

// missingRequired reports which required settings are still unset. mgsh refuses
// to start while this is non-empty.
func (c Config) missingRequired() []string {
	have := map[string]string{
		"base": c.Base, "githost": c.GitHost, "gitport": c.GitPort,
		"gituser": c.GitUser, "gitpath": c.GitPath,
	}
	var missing []string
	for _, k := range requiredKeys {
		if have[k] == "" {
			missing = append(missing, k)
		}
	}
	return missing
}

// configFile returns the path of the user config file (~/.mgshrc).
func configFile() string {
	home, _ := os.UserHomeDir()
	return filepath.Join(home, ".mgshrc")
}

// loadConfig writes an empty ~/.mgshrc template on first run, then returns the
// configuration parsed from it, overlaid with MGSH_* environment variables.
// It applies no defaults; validation of required settings is the caller's job.
func loadConfig() Config {
	path := configFile()
	if !fileExists(path) {
		writeConfigTemplate(path)
	}
	var c Config
	if data, err := os.ReadFile(path); err == nil {
		applyConfig(&c, parseConfig(string(data)))
	}
	applyEnv(&c)
	return c
}

// writeConfigTemplate creates a blank, annotated ~/.mgshrc for the user to fill
// in, migrating any aliases from the legacy ~/.mgsh_aliases file. It writes no
// real values — mgsh has no built-in configuration.
func writeConfigTemplate(path string) {
	var b strings.Builder
	b.WriteString("# mgsh configuration — fill in the required settings, then run mgsh again.\n")
	b.WriteString("# Format: 'key = value' (or 'key: value'); '#' starts a comment.\n")
	b.WriteString("# MGSH_* environment variables override these settings.\n\n")
	b.WriteString("# --- required ---\n")
	b.WriteString("base        =\n")
	b.WriteString("githost     =\n")
	b.WriteString("gitport     =\n")
	b.WriteString("gituser     =\n")
	b.WriteString("gitpath     =\n\n")
	b.WriteString("# --- optional ---\n")
	b.WriteString("# gitkey      =\n")
	b.WriteString("# gitname     = Your Name\n")
	b.WriteString("# gitemail    = you@example.com\n")
	b.WriteString("# pushdefault = matching\n")
	b.WriteString("# editor      = code\n")

	legacy := readLegacyAliases()
	if blk := aliasBlock(legacy); blk != "" {
		b.WriteString("\n" + blk)
	}

	if err := os.WriteFile(path, []byte(b.String()), 0644); err != nil {
		errorln("could not create " + path + ": " + err.Error())
		return
	}
	if len(legacy) > 0 {
		os.Remove(legacyAliasFile()) // aliases now live in ~/.mgshrc
	}
}

// parseConfig reads simple `key = value` (or `key: value`) lines, ignoring
// blank lines, `#` comments and `alias` definitions. Keys are lower-cased;
// values are unquoted.
func parseConfig(s string) map[string]string {
	m := map[string]string{}
	sc := bufio.NewScanner(strings.NewReader(s))
	for sc.Scan() {
		line := strings.TrimSpace(sc.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		if f := strings.Fields(line); len(f) > 0 && f[0] == "alias" {
			continue // alias definitions are handled by the alias loader
		}
		i := strings.IndexAny(line, "=:")
		if i < 0 {
			continue
		}
		key := strings.ToLower(strings.TrimSpace(line[:i]))
		val := strings.Trim(strings.TrimSpace(line[i+1:]), "\"'")
		m[key] = val
	}
	return m
}

func applyConfig(c *Config, m map[string]string) {
	set := func(key string, dst *string) {
		if v, ok := m[key]; ok && v != "" {
			*dst = v
		}
	}
	set("base", &c.Base)
	set("githost", &c.GitHost)
	set("gitport", &c.GitPort)
	set("gituser", &c.GitUser)
	set("gitpath", &c.GitPath)
	set("gitkey", &c.GitKey)
	set("gitname", &c.GitName)
	set("gitemail", &c.GitEmail)
	set("pushdefault", &c.PushDefault)
	set("editor", &c.Editor)
	set("remoteurl", &c.RemoteURL)
	set("remotekey", &c.RemoteKey)
	set("remotetype", &c.RemoteType)
	set("remotevisibility", &c.RemoteVis)
	set("mirror", &c.Mirror)
}

func applyEnv(c *Config) {
	env := func(key string, dst *string) {
		if v := os.Getenv(key); v != "" {
			*dst = v
		}
	}
	env("MGSH_BASE", &c.Base)
	env("MGSH_GITHOST", &c.GitHost)
	env("MGSH_GITPORT", &c.GitPort)
	env("MGSH_GITUSER", &c.GitUser)
	env("MGSH_GITPATH", &c.GitPath)
	env("MGSH_GITKEY", &c.GitKey)
	env("MGSH_GITNAME", &c.GitName)
	env("MGSH_GITEMAIL", &c.GitEmail)
	env("MGSH_PUSHDEFAULT", &c.PushDefault)
	env("MGSH_EDITOR", &c.Editor)
	env("MGSH_REMOTEURL", &c.RemoteURL)
	env("MGSH_REMOTEKEY", &c.RemoteKey)
	env("MGSH_REMOTETYPE", &c.RemoteType)
	env("MGSH_REMOTEVISIBILITY", &c.RemoteVis)
	env("MGSH_MIRROR", &c.Mirror)
}