package multiplex

import (
	"fmt"
	"math"
	"path/filepath"
	"strings"
)

// openZellij writes a layout with one tab per chunk of panes. Inside zellij
// each tab is added to the current session; outside, a new session starts.
func openZellij(panes []Pane, opts Options, r Runner) error {
	groups := chunks(panes, opts.PerWindow)
	if r.Getenv("ZELLIJ") != "" {
		for i, group := range groups {
			path := filepath.Join(opts.LayoutDir, fmt.Sprintf("netssh-multi-%d.kdl", i+1))
			tab := zellijTab(windowLabel(opts.Label, i, len(groups)), group, true)
			if err := r.WriteFile(path, []byte(zellijLayout(tab))); err != nil {
				return err
			}
			if _, err := r.Output("zellij", "action", "new-tab", "--layout", path); err != nil {
				return err
			}
			if opts.Sync {
				if _, err := r.Output("zellij", "action", "toggle-active-sync-tab"); err != nil {
					return err
				}
			}
		}
		return nil
	}
	var tabs strings.Builder
	for i, group := range groups {
		tabs.WriteString(zellijTab(windowLabel(opts.Label, i, len(groups)), group, i == 0))
	}
	path := filepath.Join(opts.LayoutDir, "netssh-multi.kdl")
	if err := r.WriteFile(path, []byte(zellijLayout(tabs.String()))); err != nil {
		return err
	}
	if opts.Sync {
		opts.Hint("zellij starts without broadcast: press Ctrl+t, then s, to type into all panes")
	} else {
		opts.Hint("toggle broadcast with Ctrl+t, then s (or netssh sync)")
	}
	return r.Exec("zellij", "--layout", path)
}

// zellijLayout wraps tabs with zellij's tab and status bars.
func zellijLayout(tabs string) string {
	return `layout {
    default_tab_template {
        pane size=1 borderless=true {
            plugin location="zellij:tab-bar"
        }
        children
        pane size=2 borderless=true {
            plugin location="zellij:status-bar"
        }
    }
` + tabs + "}\n"
}

// zellijTab arranges panes in a grid: rows of ceil(sqrt(n)) columns.
func zellijTab(name string, panes []Pane, focus bool) string {
	cols := int(math.Ceil(math.Sqrt(float64(len(panes)))))
	var b strings.Builder
	fmt.Fprintf(&b, "    tab name=%s", kdlString(name))
	if focus {
		b.WriteString(" focus=true")
	}
	b.WriteString(" {\n")
	for start := 0; start < len(panes); start += cols {
		row := panes[start:min(start+cols, len(panes))]
		indent := "        "
		if len(row) > 1 {
			b.WriteString(indent + "pane split_direction=\"vertical\" {\n")
			indent += "    "
		}
		for _, p := range row {
			fmt.Fprintf(&b, "%spane name=%s command=%s {\n", indent, kdlString(p.Title), kdlString(p.Argv[0]))
			if len(p.Argv) > 1 {
				args := make([]string, 0, len(p.Argv)-1)
				for _, arg := range p.Argv[1:] {
					args = append(args, kdlString(arg))
				}
				fmt.Fprintf(&b, "%s    args %s\n", indent, strings.Join(args, " "))
			}
			b.WriteString(indent + "}\n")
		}
		if len(row) > 1 {
			b.WriteString("        }\n")
		}
	}
	b.WriteString("    }\n")
	return b.String()
}

// kdlString quotes s as a KDL string.
func kdlString(s string) string {
	return `"` + strings.NewReplacer(`\`, `\\`, `"`, `\"`, "\n", `\n`).Replace(s) + `"`
}