package daemon

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"net"
	"strings"
	"time"

	"banger/internal/api"
	sess "banger/internal/daemon/session"
	ws "banger/internal/daemon/workspace"
	"banger/internal/model"
	"banger/internal/system"
)

func (d *Daemon) ExportVMWorkspace(ctx context.Context, params api.WorkspaceExportParams) (api.WorkspaceExportResult, error) {
	guestPath := strings.TrimSpace(params.GuestPath)
	if guestPath == "" {
		guestPath = "/root/repo"
	}
	vm, err := d.FindVM(ctx, params.IDOrName)
	if err != nil {
		return api.WorkspaceExportResult{}, err
	}
	if vm.State != model.VMStateRunning || !system.ProcessRunning(vm.Runtime.PID, vm.Runtime.APISockPath) {
		return api.WorkspaceExportResult{}, fmt.Errorf("vm %q is not running", vm.Name)
	}
	client, err := d.dialGuest(ctx, net.JoinHostPort(vm.Runtime.GuestIP, "22"))
	if err != nil {
		return api.WorkspaceExportResult{}, fmt.Errorf("dial guest: %w", err)
	}
	defer client.Close()

	// diffRef is the git ref everything is diffed against.
	// When the caller supplies BaseCommit (the HEAD at workspace.prepare time),
	// we diff against that fixed point so committed guest changes are included.
	// Without it we fall back to HEAD, which silently drops them.
	diffRef := strings.TrimSpace(params.BaseCommit)
	if diffRef == "" {
		diffRef = "HEAD"
	}

	// Stage all changes then emit a binary-safe unified diff against diffRef.
	// After git add -A the index contains the full working state, so
	// git diff --cached <diffRef> captures both committed deltas (HEAD moved
	// past diffRef) and any additional uncommitted changes on top.
	patchScript := fmt.Sprintf(
		"set -euo pipefail\ncd %s\ngit add -A\ngit diff --cached %s --binary\n",
		sess.ShellQuote(guestPath),
		sess.ShellQuote(diffRef),
	)
	patch, err := client.RunScriptOutput(ctx, patchScript)
	if err != nil {
		return api.WorkspaceExportResult{}, fmt.Errorf("export workspace diff: %w", err)
	}

	// Enumerate changed paths (index already staged; this is a cheap read).
	namesScript := fmt.Sprintf(
		"set -euo pipefail\ncd %s\ngit diff --cached %s --name-only\n",
		sess.ShellQuote(guestPath),
		sess.ShellQuote(diffRef),
	)
	namesOut, _ := client.RunScriptOutput(ctx, namesScript)
	var changed []string
	for _, line := range strings.Split(strings.TrimSpace(string(namesOut)), "\n") {
		if line = strings.TrimSpace(line); line != "" {
			changed = append(changed, line)
		}
	}

	return api.WorkspaceExportResult{
		GuestPath:    guestPath,
		BaseCommit:   diffRef,
		Patch:        patch,
		ChangedFiles: changed,
		HasChanges:   len(patch) > 0,
	}, nil
}

func (d *Daemon) PrepareVMWorkspace(ctx context.Context, params api.VMWorkspacePrepareParams) (model.WorkspacePrepareResult, error) {
	mode, err := ws.ParsePrepareMode(params.Mode)
	if err != nil {
		return model.WorkspacePrepareResult{}, err
	}
	guestPath := strings.TrimSpace(params.GuestPath)
	if guestPath == "" {
		guestPath = "/root/repo"
	}
	branchName := strings.TrimSpace(params.Branch)
	fromRef := strings.TrimSpace(params.From)
	if branchName != "" && fromRef == "" {
		fromRef = "HEAD"
	}
	if branchName == "" && strings.TrimSpace(params.From) != "" {
		return model.WorkspacePrepareResult{}, errors.New("workspace from requires branch")
	}
	var prepared model.WorkspacePrepareResult
	_, err = d.withVMLockByRef(ctx, params.IDOrName, func(vm model.VMRecord) (model.VMRecord, error) {
		if vm.State != model.VMStateRunning || !system.ProcessRunning(vm.Runtime.PID, vm.Runtime.APISockPath) {
			return model.VMRecord{}, fmt.Errorf("vm %q is not running", vm.Name)
		}
		result, err := d.prepareVMWorkspaceLocked(ctx, vm, strings.TrimSpace(params.SourcePath), guestPath, branchName, fromRef, mode, params.ReadOnly)
		if err != nil {
			return model.VMRecord{}, err
		}
		prepared = result
		return vm, nil
	})
	return prepared, err
}

func (d *Daemon) prepareVMWorkspaceLocked(ctx context.Context, vm model.VMRecord, sourcePath, guestPath, branchName, fromRef string, mode model.WorkspacePrepareMode, readOnly bool) (model.WorkspacePrepareResult, error) {
	spec, err := ws.InspectRepo(ctx, sourcePath, branchName, fromRef)
	if err != nil {
		return model.WorkspacePrepareResult{}, err
	}
	if len(spec.Submodules) > 0 && mode != model.WorkspacePrepareModeFullCopy {
		return model.WorkspacePrepareResult{}, fmt.Errorf("workspace mode %q does not support git submodules in %s (%s); use --mode full_copy", mode, spec.RepoRoot, strings.Join(spec.Submodules, ", "))
	}
	address := net.JoinHostPort(vm.Runtime.GuestIP, "22")
	if err := d.waitForGuestSSH(ctx, address, 250*time.Millisecond); err != nil {
		return model.WorkspacePrepareResult{}, fmt.Errorf("guest ssh unavailable: %w", err)
	}
	client, err := d.dialGuest(ctx, address)
	if err != nil {
		return model.WorkspacePrepareResult{}, fmt.Errorf("dial guest ssh: %w", err)
	}
	defer client.Close()
	if err := ws.ImportRepoToGuest(ctx, client, spec, guestPath, mode); err != nil {
		return model.WorkspacePrepareResult{}, err
	}
	if readOnly {
		var chmodLog bytes.Buffer
		chmodScript := fmt.Sprintf("set -euo pipefail\nchmod -R a-w %s\n", sess.ShellQuote(guestPath))
		if err := client.RunScript(ctx, chmodScript, &chmodLog); err != nil {
			return model.WorkspacePrepareResult{}, sess.FormatStepError("set workspace readonly", err, chmodLog.String())
		}
	}
	return model.WorkspacePrepareResult{
		VMID:          vm.ID,
		SourcePath:    spec.SourcePath,
		RepoRoot:      spec.RepoRoot,
		RepoName:      spec.RepoName,
		GuestPath:     guestPath,
		Mode:          mode,
		ReadOnly:      readOnly,
		HeadCommit:    spec.HeadCommit,
		CurrentBranch: spec.CurrentBranch,
		BranchName:    spec.BranchName,
		BaseCommit:    spec.BaseCommit,
		PreparedAt:    model.Now(),
	}, nil
}