package tools

import (
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"

	"gitea.d-ma.be/mathias/gitea-mcp/internal/allowlist"
	"gitea.d-ma.be/mathias/gitea-mcp/internal/gitea"
	"gitea.d-ma.be/mathias/gitea-mcp/internal/registry"
)

const fileReadMaxBytes = 1 << 20 // 1 MiB

type FileRead struct {
	c *gitea.Client
	a *allowlist.Allowlist
}

func NewFileRead(c *gitea.Client, a *allowlist.Allowlist) *FileRead {
	return &FileRead{c: c, a: a}
}

func (t *FileRead) Descriptor() registry.ToolDescriptor {
	return registry.ToolDescriptor{
		Name:        "file_read",
		Description: "Read a file from a repo at a given ref. Defaults to the repo's default branch.",
		InputSchema: json.RawMessage(`{
			"type":"object",
			"properties":{
				"owner":{"type":"string"},
				"name":{"type":"string"},
				"path":{"type":"string"},
				"ref":{"type":"string"}
			},
			"required":["owner","name","path"]
		}`),
	}
}

type fileReadArgs struct {
	Owner string `json:"owner"`
	Name  string `json:"name"`
	Path  string `json:"path"`
	Ref   string `json:"ref"`
}

func (t *FileRead) Call(ctx context.Context, raw json.RawMessage) (json.RawMessage, error) {
	var args fileReadArgs
	if err := parseArgs(raw, &args); err != nil {
		return nil, err
	}
	if err := t.a.Check(args.Owner); err != nil {
		return nil, err
	}

	ref := args.Ref
	if ref == "" {
		repo, err := t.c.GetRepo(ctx, args.Owner, args.Name)
		if err != nil {
			return nil, err
		}
		ref = repo.DefaultBranch
	}

	fc, err := t.c.GetFileContents(ctx, args.Owner, args.Name, args.Path, ref)
	if err != nil {
		return nil, err
	}

	if fc.Size > fileReadMaxBytes {
		return nil, fmt.Errorf("file %q size %d exceeds 1MiB cap: %w", args.Path, fc.Size, gitea.ErrValidation)
	}

	decoded, err := base64.StdEncoding.DecodeString(fc.Content)
	if err != nil {
		return nil, fmt.Errorf("decode base64 content: %w", err)
	}

	return textOK(map[string]any{
		"path":    fc.Path,
		"ref":     ref,
		"sha":     fc.Sha,
		"size":    fc.Size,
		"content": string(decoded),
	})
}