-- Query execution engine module
local M = {}

local database = require('notex.database.init')
local query_builder = require('notex.query.builder')
local query_parser = require('notex.query.parser')
local utils = require('notex.utils')

-- Execute parsed query
function M.execute(parsed_query, options)
  options = options or {}
  local start_time = vim.loop.hrtime()

  local result = {
    documents = {},
    total_count = 0,
    execution_time_ms = 0,
    query_hash = "",
    success = false,
    errors = {},
    metadata = {}
  }

  -- Validate parsed query
  if #parsed_query.parse_errors > 0 then
    result.errors = parsed_query.parse_errors
    result.error_type = "parse_error"
    return result
  end

  -- Generate query hash
  result.query_hash = query_parser.generate_query_hash(parsed_query)

  -- Build SQL query
  local sql, params = query_builder.build_sql(parsed_query, options)
  if not sql then
    table.insert(result.errors, "Failed to build SQL query")
    result.error_type = "build_error"
    return result
  end

  -- Validate SQL
  local valid, validation_error = query_builder.validate_sql(sql)
  if not valid then
    table.insert(result.errors, validation_error)
    result.error_type = "validation_error"
    return result
  end

  -- Execute query
  local ok, query_result = database.execute(sql, params)
  if not ok then
    table.insert(result.errors, "Query execution failed: " .. query_result)
    result.error_type = "execution_error"
    return result
  end

  -- Process results
  local processed_results = M.process_query_results(query_result, parsed_query, options)
  result.documents = processed_results.documents
  result.metadata = processed_results.metadata

  -- Get total count
  result.total_count = M.get_total_count(parsed_query, options)

  -- Calculate execution time
  local end_time = vim.loop.hrtime()
  result.execution_time_ms = (end_time - start_time) / 1e6

  result.success = true

  -- Log slow queries
  if result.execution_time_ms > 100 then
    utils.log("WARN", string.format("Slow query detected: %.2fms", result.execution_time_ms), {
      query_hash = result.query_hash,
      document_count = #result.documents
    })
  end

  return result
end

-- Process query results
function M.process_query_results(raw_results, parsed_query, options)
  local documents = {}
  local metadata = {
    properties_found = {},
    aggregation_results = {}
  }

  -- Group results by document if we have properties
  local documents_by_id = {}
  for _, row in ipairs(raw_results) do
    local doc_id = row.id

    if not documents_by_id[doc_id] then
      documents_by_id[doc_id] = {
        id = doc_id,
        file_path = row.file_path,
        content_hash = row.content_hash,
        last_modified = row.last_modified,
        created_at = row.created_at,
        updated_at = row.updated_at,
        properties = {}
      }
    end

    -- Add properties from result row
    for key, value in pairs(row) do
      if key ~= "id" and key ~= "file_path" and key ~= "content_hash" and
         key ~= "last_modified" and key ~= "created_at" and key ~= "updated_at" then
        if value and value ~= "" then
          documents_by_id[doc_id].properties[key] = value
          metadata.properties_found[key] = true
        end
      end
    end
  end

  -- Convert to array
  for _, doc in pairs(documents_by_id) do
    table.insert(documents, doc)
  end

  -- Apply post-processing filters
  documents = M.apply_post_filters(documents, parsed_query, options)

  -- Apply sorting if not handled by SQL
  if parsed_query.order_by and parsed_query.order_by.field == "relevance" then
    documents = M.sort_by_relevance(documents, parsed_query)
  end

  return {
    documents = documents,
    metadata = metadata
  }
end

-- Apply post-processing filters
function M.apply_post_filters(documents, parsed_query, options)
  local filtered = documents

  -- Apply text search highlighting if requested
  if options.highlight and parsed_query.conditions then
    filtered = M.apply_text_highlighting(filtered, parsed_query)
  end

  -- Apply additional filters that couldn't be handled by SQL
  filtered = M.apply_complex_filters(filtered, parsed_query)

  return filtered
end

-- Apply text highlighting
function M.apply_text_highlighting(documents, parsed_query)
  -- Implementation for text highlighting
  -- This would mark matching text in document properties
  return documents
end

-- Apply complex filters
function M.apply_complex_filters(documents, parsed_query)
  local filtered = {}

  for _, doc in ipairs(documents) do
    local include = true

    -- Apply any complex filter logic here
    if include then
      table.insert(filtered, doc)
    end
  end

  return filtered
end

-- Sort by relevance
function M.sort_by_relevance(documents, parsed_query)
  -- Simple relevance scoring based on filter matches
  local scored = {}

  for _, doc in ipairs(documents) do
    local score = 0

    -- Score based on filter matches
    for field, _ in pairs(parsed_query.filters) do
      if doc.properties[field] then
        score = score + 1
      end
    end

    -- Add document with score
    table.insert(scored, {
      document = doc,
      score = score
    })
  end

  -- Sort by score (descending)
  table.sort(scored, function(a, b) return a.score > b.score end)

  -- Extract documents
  local sorted_documents = {}
  for _, item in ipairs(scored) do
    table.insert(sorted_documents, item.document)
  end

  return sorted_documents
end

-- Get total count for query
function M.get_total_count(parsed_query, options)
  local count_sql, count_params = query_builder.build_count_query(parsed_query, options)

  local ok, count_result = database.execute(count_sql, count_params)
  if not ok then
    utils.log("ERROR", "Failed to get total count", { error = count_result })
    return 0
  end

  return count_result[1] and count_result[1].total_count or 0
end

-- Execute query with caching
function M.execute_cached(parsed_query, options)
  options = options or {}
  local cache_enabled = options.cache ~= false

  if not cache_enabled then
    return M.execute(parsed_query, options)
  end

  local query_hash = query_parser.generate_query_hash(parsed_query)
  local cache_key = "query:" .. query_hash

  -- Check cache (implementation would depend on cache system)
  -- For now, just execute directly
  return M.execute(parsed_query, options)
end

-- Validate query before execution
function M.validate_query(parsed_query)
  local errors = {}

  -- Check for required fields
  if not parsed_query or not parsed_query.filters then
    table.insert(errors, "Query must have filters")
  end

  -- Validate filter values
  for field, value in pairs(parsed_query.filters or {}) do
    if not M.is_valid_filter_value(value) then
      table.insert(errors, string.format("Invalid filter value for field '%s'", field))
    end
  end

  -- Validate conditions
  if parsed_query.conditions then
    M.validate_conditions_recursive(parsed_query.conditions, errors)
  end

  return #errors == 0, errors
end

-- Check if filter value is valid
function M.is_valid_filter_value(value)
  if type(value) == "string" and #value > 1000 then
    return false
  end

  if type(value) == "table" and #value > 100 then
    return false
  end

  return true
end

-- Validate conditions recursively
function M.validate_conditions_recursive(conditions, errors)
  if conditions.type == "comparison" then
    if not conditions.field or not conditions.operator or conditions.value == nil then
      table.insert(errors, "Invalid comparison condition")
    end
  elseif conditions.type == "existence" then
    if not conditions.field then
      table.insert(errors, "Invalid existence condition")
    end
  elseif conditions.clauses then
    for _, clause in ipairs(conditions.clauses) do
      M.validate_conditions_recursive(clause, errors)
    end
  end
end

-- Get query suggestions
function M.get_suggestions(partial_query, options)
  local suggestions = {
    properties = {},
    values = {},
    operators = {}
  }

  -- Get property suggestions from schema
  local ok, schema_result = database.execute("SELECT DISTINCT property_key FROM schema_metadata ORDER BY document_count DESC LIMIT 20")
  if ok then
    for _, row in ipairs(schema_result) do
      table.insert(suggestions.properties, row.property_key)
    end
  end

  -- Get value suggestions for common properties
  local common_properties = {"status", "priority", "tags", "type"}
  for _, prop in ipairs(common_properties) do
    local ok, values_result = database.execute(
      "SELECT DISTINCT value FROM properties WHERE key = ? AND value_type = 'string' LIMIT 10",
      { prop }
    )
    if ok then
      suggestions.values[prop] = {}
      for _, row in ipairs(values_result) do
        table.insert(suggestions.values[prop], row.value)
      end
    end
  end

  -- Common operators
  suggestions.operators = {"=", "!=", ">", "<", ">=", "<=", "CONTAINS", "STARTS_WITH", "ENDS_WITH", "INCLUDES"}

  return suggestions
end

-- Explain query execution plan
function M.explain_query(parsed_query, options)
  local sql, params = query_builder.build_sql(parsed_query, options)

  local explain_sql = "EXPLAIN QUERY PLAN " .. sql
  local ok, explain_result = database.execute(explain_sql, params)

  if not ok then
    return {
      success = false,
      error = explain_result,
      sql = sql
    }
  end

  return {
    success = true,
    sql = sql,
    params = params,
    plan = explain_result,
    estimated_cost = M.calculate_query_cost(explain_result)
  }
end

-- Calculate query cost
function M.calculate_query_cost(explain_result)
  local total_cost = 0

  for _, row in ipairs(explain_result) do
    -- Simple cost calculation based on SQLite's EXPLAIN output
    if row.detail and row.detail:match("SCAN") then
      total_cost = total_cost + 10
    elseif row.detail and row.detail:match("SEARCH") then
      total_cost = total_cost + 2
    else
      total_cost = total_cost + 1
    end
  end

  return total_cost
end

return M