// session — environment scanning from xsessions, wayland-sessions,
// and custom script directories. Includes desktop entry parser.
//
// Mirrors vendor/src/post_login/mod.rs:get_envs and parse_desktop_entry.
package session

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

type DesktopEntry struct {
	Name         string
	Exec         string
	DesktopNames string
	Hidden       bool
	NoDisplay    bool
}

func parseDesktopEntry(path string) (*DesktopEntry, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, fmt.Errorf("open %s: %w", path, err)
	}
	defer f.Close()

	e := &DesktopEntry{}
	inSection := false
	sc := bufio.NewScanner(f)
	for sc.Scan() {
		line := strings.TrimSpace(sc.Text())
		if line == "" || line[0] == '#' {
			continue
		}
		if line[0] == '[' && line[len(line)-1] == ']' {
			inSection = line == "[Desktop Entry]"
			continue
		}
		if !inSection {
			continue
		}
		eq := strings.IndexByte(line, '=')
		if eq < 0 {
			continue
		}
		k, v := line[:eq], line[eq+1:]
		switch k {
		case "Name":
			e.Name = v
		case "Exec":
			e.Exec = v
		case "DesktopNames":
			e.DesktopNames = v
		case "Hidden":
			e.Hidden = strings.EqualFold(v, "true")
		case "NoDisplay":
			e.NoDisplay = strings.EqualFold(v, "true")
		}
	}
	if sc.Err() != nil {
		return nil, sc.Err()
	}
	if e.Exec == "" {
		return nil, fmt.Errorf("no Exec in %s", path)
	}
	if e.Name == "" {
		e.Name = e.Exec
	}
	return e, nil
}

func ScanEnvs(xSessions, wlSessions, xScripts, wlScripts string, includeTTY bool) []PostLoginEnv {
	var envs []PostLoginEnv

	scanDesktopDir(xSessions, "x11", &envs)
	scanDesktopDir(wlSessions, "wayland", &envs)
	scanScriptDir(xScripts, "x11", &envs)
	scanScriptDir(wlScripts, "wayland", &envs)

	if len(envs) == 0 || includeTTY {
		envs = append(envs, PostLoginEnv{Kind: "tty", Title: "TTYSHELL"})
	}
	return envs
}

func scanDesktopDir(dir, kind string, envs *[]PostLoginEnv) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return
	}
	for _, e := range entries {
		if e.IsDir() || filepath.Ext(e.Name()) != ".desktop" {
			continue
		}
		path := filepath.Join(dir, e.Name())
		de, err := parseDesktopEntry(path)
		if err != nil || de.Hidden || de.NoDisplay {
			continue
		}
		desktopNames, sessionDesktop := splitDesktopNames(de.DesktopNames, e.Name())
		*envs = append(*envs, PostLoginEnv{
			Kind:           kind,
			Title:          de.Name,
			XinitrcPath:    de.Exec,
			ScriptPath:     de.Exec,
			DesktopNames:   desktopNames,
			SessionDesktop: sessionDesktop,
		})
	}
}

func splitDesktopNames(raw, fallback string) (currentDesktop, sessionDesktop string) {
	if raw == "" {
		return fallback, fallback
	}
	parts := strings.SplitN(raw, ";", 2)
	sessionDesktop = strings.TrimSpace(parts[0])
	currentDesktop = strings.ReplaceAll(raw, ";", ":")
	return
}

func scanScriptDir(dir, kind string, envs *[]PostLoginEnv) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return
	}
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		info, err := e.Info()
		if err != nil {
			continue
		}
		if info.Mode()&0111 == 0 {
			continue
		}
		path := filepath.Join(dir, e.Name())
		*envs = append(*envs, PostLoginEnv{
			Kind:        kind,
			Title:       e.Name(),
			XinitrcPath: path,
			ScriptPath:  path,
		})
	}
}