// Package officekit creates and edits real, native Office Open XML
// files — .docx (Word), .xlsx (Excel), .pptx (PowerPoint) — as plain
// Go structs and byte slices, with no dependency beyond the standard
// library (archive/zip + encoding/xml).
//
// # Why this package exists
//
// enkly's agent talks to a Qwen model through a vLLM OpenAI-compatible
// tool-calling API (pkg/vllmkit). Tool calls and tool results travel
// as structured JSON on that wire (an "arguments" string vLLM's
// tool-call parser extracts from the model's raw generation), not
// wrapped in the XML-ish chat-template delimiters an Ollama deployment
// of this same model would have used — so the specific "XML syntax
// error on line N" failure mode an earlier, Ollama-backed version of
// this service saw when a tool result contained raw angle-bracket
// markup no longer applies verbatim. vLLM's tool-call parser can still
// fail to extract a clean call from the model's output, surfaced
// client-side as vllmkit.IsToolCallParseError (see
// agentrun/agent.go's compactToolHistory doc comment for the retry
// strategy built on top of it) — a different failure mode, but the
// same underlying risk: anything that makes the model's raw output
// harder for its tool-call parser to read is worth avoiding.
//
// The structural fix lives here regardless of transport: the model
// NEVER authors or receives OOXML. It only ever calls a tool with
// plain structured arguments
// (a title, a list of paragraphs, a grid of cell values, a list of
// slide bullets) and gets back a short plain-text summary. This
// package does 100% of the actual XML generation and parsing,
// server-side, using Go's typed XML encoder/decoder (which always
// produces well-formed, correctly-escaped XML) — and the resulting
// bytes travel to/from the workspace service over the existing
// UploadFile/DownloadFile RPCs, which carry raw []byte, not the
// text-oriented ReadFile/WriteFile string fields. No proto changes,
// no binary-over-text encoding, and no XML ever touches the LLM.
package officekit

import (
	"archive/zip"
	"bytes"
	"fmt"
	"io"
)

// zipPart is one file inside an OOXML package (which is just a zip
// archive with a prescribed internal layout).
type zipPart struct {
	Name string
	Body string
}

// buildZip packages parts into an OOXML container. Office is picky
// about [Content_Types].xml being present; beyond that, part order
// doesn't matter to any reader in practice, but we write it first
// anyway since that's the convention most real Office-authored files
// follow.
func buildZip(parts []zipPart) ([]byte, error) {
	var buf bytes.Buffer
	zw := zip.NewWriter(&buf)
	for _, p := range parts {
		w, err := zw.Create(p.Name)
		if err != nil {
			return nil, fmt.Errorf("officekit: create %s: %w", p.Name, err)
		}
		if _, err := w.Write([]byte(p.Body)); err != nil {
			return nil, fmt.Errorf("officekit: write %s: %w", p.Name, err)
		}
	}
	if err := zw.Close(); err != nil {
		return nil, fmt.Errorf("officekit: close zip: %w", err)
	}
	return buf.Bytes(), nil
}

// readZipPart extracts one named part's raw bytes from an OOXML
// package, or returns ok=false if it isn't present.
func readZipPart(data []byte, name string) ([]byte, bool, error) {
	zr, err := zip.NewReader(bytes.NewReader(data), int64(len(data)))
	if err != nil {
		return nil, false, fmt.Errorf("officekit: not a valid Office file (not a zip archive): %w", err)
	}
	for _, f := range zr.File {
		if f.Name == name {
			rc, err := f.Open()
			if err != nil {
				return nil, false, fmt.Errorf("officekit: open %s: %w", name, err)
			}
			defer rc.Close()
			var buf bytes.Buffer
			if _, err := buf.ReadFrom(rc); err != nil {
				return nil, false, fmt.Errorf("officekit: read %s: %w", name, err)
			}
			return buf.Bytes(), true, nil
		}
	}
	return nil, false, nil
}

// addZipParts returns a copy of an OOXML package with every existing
// part copied through unchanged, plus the given new parts appended
// (used by AppendPptxSlide to add a slideN.xml/slideN.xml.rels pair
// without disturbing anything already in the archive).
func addZipParts(data []byte, newParts []zipPart) ([]byte, error) {
	zr, err := zip.NewReader(bytes.NewReader(data), int64(len(data)))
	if err != nil {
		return nil, fmt.Errorf("officekit: not a valid Office file (not a zip archive): %w", err)
	}
	var buf bytes.Buffer
	zw := zip.NewWriter(&buf)
	for _, f := range zr.File {
		w, err := zw.Create(f.Name)
		if err != nil {
			return nil, fmt.Errorf("officekit: create %s: %w", f.Name, err)
		}
		rc, err := f.Open()
		if err != nil {
			return nil, fmt.Errorf("officekit: open %s: %w", f.Name, err)
		}
		_, copyErr := io.Copy(w, rc)
		rc.Close()
		if copyErr != nil {
			return nil, fmt.Errorf("officekit: copy %s: %w", f.Name, copyErr)
		}
	}
	for _, p := range newParts {
		w, err := zw.Create(p.Name)
		if err != nil {
			return nil, fmt.Errorf("officekit: create %s: %w", p.Name, err)
		}
		if _, err := w.Write([]byte(p.Body)); err != nil {
			return nil, fmt.Errorf("officekit: write %s: %w", p.Name, err)
		}
	}
	if err := zw.Close(); err != nil {
		return nil, fmt.Errorf("officekit: close zip: %w", err)
	}
	return buf.Bytes(), nil
}

// replaceZipPart returns a copy of an OOXML package with one part's
// body replaced (used by the edit_* operations: download, patch one
// XML part, re-upload). Every other part is copied through unchanged.
func replaceZipPart(data []byte, name string, newBody []byte) ([]byte, error) {
	zr, err := zip.NewReader(bytes.NewReader(data), int64(len(data)))
	if err != nil {
		return nil, fmt.Errorf("officekit: not a valid Office file (not a zip archive): %w", err)
	}

	var buf bytes.Buffer
	zw := zip.NewWriter(&buf)
	replaced := false
	for _, f := range zr.File {
		w, err := zw.Create(f.Name)
		if err != nil {
			return nil, fmt.Errorf("officekit: create %s: %w", f.Name, err)
		}
		if f.Name == name {
			replaced = true
			if _, err := w.Write(newBody); err != nil {
				return nil, fmt.Errorf("officekit: write %s: %w", f.Name, err)
			}
			continue
		}
		rc, err := f.Open()
		if err != nil {
			return nil, fmt.Errorf("officekit: open %s: %w", f.Name, err)
		}
		_, copyErr := io.Copy(w, rc)
		rc.Close()
		if copyErr != nil {
			return nil, fmt.Errorf("officekit: copy %s: %w", f.Name, copyErr)
		}
	}
	if !replaced {
		return nil, fmt.Errorf("officekit: part %s not found in archive", name)
	}
	if err := zw.Close(); err != nil {
		return nil, fmt.Errorf("officekit: close zip: %w", err)
	}
	return buf.Bytes(), nil
}