local str = require("string")
local tbl = require("table")
local postgres = {}

local Connection = {}
Connection.__index = Connection

function Connection:close()
	if self._id then
		local ok = moonshark.sql_close(self._id)
		self._id = nil
		return ok
	end
	return false
end

function Connection:ping()
	if not self._id then
		error("Connection is closed")
	end
	return moonshark.sql_ping(self._id)
end

function Connection:query(query_str, ...)
	if not self._id then
		error("Connection is closed")
	end
	query_str = str.normalize_whitespace(query_str)
	return moonshark.sql_query(self._id, query_str, ...)
end

function Connection:exec(query_str, ...)
	if not self._id then
		error("Connection is closed")
	end
	query_str = str.normalize_whitespace(query_str)
	return moonshark.sql_exec(self._id, query_str, ...)
end

function Connection:query_row(query_str, ...)
	local results = self:query(query_str, ...)
	if results and #results > 0 then
		return results[1]
	end
	return nil
end

function Connection:query_value(query_str, ...)
	local row = self:query_row(query_str, ...)
	if row then
		for _, value in pairs(row) do
			return value
		end
	end
	return nil
end

-- Enhanced transaction support with savepoints
function Connection:begin()
	local result = self:exec("BEGIN")
	if result then
		return {
			conn = self,
			active = true,

			commit = function(tx)
				if tx.active then
					local result = tx.conn:exec("COMMIT")
					tx.active = false
					return result
				end
				return false
			end,

			rollback = function(tx)
				if tx.active then
					local result = tx.conn:exec("ROLLBACK")
					tx.active = false
					return result
				end
				return false
			end,

			savepoint = function(tx, name)
				if not tx.active then
					error("Transaction is not active")
				end
				if str.is_blank(name) then
					error("Savepoint name cannot be empty")
				end
				return tx.conn:exec(str.template("SAVEPOINT ${name}", {name = name}))
			end,

			rollback_to = function(tx, name)
				if not tx.active then
					error("Transaction is not active")
				end
				if str.is_blank(name) then
					error("Savepoint name cannot be empty")
				end
				return tx.conn:exec(str.template("ROLLBACK TO SAVEPOINT ${name}", {name = name}))
			end,

			query = function(tx, query_str, ...)
				if not tx.active then
					error("Transaction is not active")
				end
				return tx.conn:query(query_str, ...)
			end,

			exec = function(tx, query_str, ...)
				if not tx.active then
					error("Transaction is not active")
				end
				return tx.conn:exec(query_str, ...)
			end,

			query_row = function(tx, query_str, ...)
				if not tx.active then
					error("Transaction is not active")
				end
				return tx.conn:query_row(query_str, ...)
			end,

			query_value = function(tx, query_str, ...)
				if not tx.active then
					error("Transaction is not active")
				end
				return tx.conn:query_value(query_str, ...)
			end
		}
	end
	return nil
end

-- Simplified PostgreSQL parameter builder
local function build_postgres_params(data)
	local keys = tbl.keys(data)
	local values = tbl.values(data)
	local placeholders = {}

	for i = 1, #keys do
		tbl.insert(placeholders, str.template("$${num}", {num = tostring(i)}))
	end

	return keys, values, placeholders, #keys
end

-- Simplified query builders using table utilities
function Connection:insert(table_name, data, returning)
	if str.is_blank(table_name) then
		error("Table name cannot be empty")
	end

	local keys, values, placeholders = build_postgres_params(data)

	local query = str.template("INSERT INTO ${table} (${columns}) VALUES (${placeholders})", {
		table = table_name,
		columns = tbl.concat(keys, ", "),
		placeholders = tbl.concat(placeholders, ", ")
	})

	if returning and not str.is_blank(returning) then
		query = str.template("${query} RETURNING ${returning}", {
			query = query,
			returning = returning
		})
		return self:query(query, unpack(values))
	else
		return self:exec(query, unpack(values))
	end
end

function Connection:upsert(table_name, data, conflict_columns, returning)
	if str.is_blank(table_name) then
		error("Table name cannot be empty")
	end

	local keys, values, placeholders = build_postgres_params(data)
	local updates = tbl.map(keys, function(key)
		return str.template("${key} = EXCLUDED.${key}", {key = key})
	end)

	local conflict_clause = ""
	if conflict_columns then
		if type(conflict_columns) == "string" then
			conflict_clause = str.template("(${columns})", {columns = conflict_columns})
		else
			conflict_clause = str.template("(${columns})", {columns = tbl.concat(conflict_columns, ", ")})
		end
	end

	local query = str.template("INSERT INTO ${table} (${columns}) VALUES (${placeholders}) ON CONFLICT ${conflict} DO UPDATE SET ${updates}", {
		table = table_name,
		columns = tbl.concat(keys, ", "),
		placeholders = tbl.concat(placeholders, ", "),
		conflict = conflict_clause,
		updates = tbl.concat(updates, ", ")
	})

	if returning and not str.is_blank(returning) then
		query = str.template("${query} RETURNING ${returning}", {
			query = query,
			returning = returning
		})
		return self:query(query, unpack(values))
	else
		return self:exec(query, unpack(values))
	end
end

function Connection:update(table_name, data, where_clause, returning, ...)
	if str.is_blank(table_name) then
		error("Table name cannot be empty")
	end
	if str.is_blank(where_clause) then
		error("WHERE clause cannot be empty for UPDATE")
	end

	local keys = tbl.keys(data)
	local values = tbl.values(data)
	local param_count = #keys

	local sets = {}
	for i, key in ipairs(keys) do
		tbl.insert(sets, str.template("${key} = $${num}", {
			key = key,
			num = tostring(i)
		}))
	end

	-- Handle WHERE clause parameters
	local where_args = {...}
	local where_clause_with_params = where_clause
	for i = 1, #where_args do
		param_count = param_count + 1
		tbl.insert(values, where_args[i])
		where_clause_with_params = str.replace(where_clause_with_params, "?",
			str.template("$${num}", {num = tostring(param_count)}), 1)
	end

	local query = str.template("UPDATE ${table} SET ${sets} WHERE ${where}", {
		table = table_name,
		sets = tbl.concat(sets, ", "),
		where = where_clause_with_params
	})

	if returning and not str.is_blank(returning) then
		query = str.template("${query} RETURNING ${returning}", {
			query = query,
			returning = returning
		})
		return self:query(query, unpack(values))
	else
		return self:exec(query, unpack(values))
	end
end

function Connection:delete(table_name, where_clause, returning, ...)
	if str.is_blank(table_name) then
		error("Table name cannot be empty")
	end
	if str.is_blank(where_clause) then
		error("WHERE clause cannot be empty for DELETE")
	end

	-- Handle WHERE clause parameters
	local where_args = {...}
	local values = {}
	local where_clause_with_params = where_clause
	for i = 1, #where_args do
		tbl.insert(values, where_args[i])
		where_clause_with_params = str.replace(where_clause_with_params, "?",
			str.template("$${num}", {num = tostring(i)}), 1)
	end

	local query = str.template("DELETE FROM ${table} WHERE ${where}", {
		table = table_name,
		where = where_clause_with_params
	})

	if returning and not str.is_blank(returning) then
		query = str.template("${query} RETURNING ${returning}", {
			query = query,
			returning = returning
		})
		return self:query(query, unpack(values))
	else
		return self:exec(query, unpack(values))
	end
end

function Connection:select(table_name, columns, where_clause, ...)
	if str.is_blank(table_name) then
		error("Table name cannot be empty")
	end

	columns = columns or "*"
	if type(columns) == "table" then
		columns = tbl.concat(columns, ", ")
	end

	local query
	if where_clause and not str.is_blank(where_clause) then
		-- Handle WHERE clause parameters
		local where_args = {...}
		local values = {}
		local where_clause_with_params = where_clause
		for i = 1, #where_args do
			tbl.insert(values, where_args[i])
			where_clause_with_params = str.replace(where_clause_with_params, "?",
				str.template("$${num}", {num = tostring(i)}), 1)
		end

		query = str.template("SELECT ${columns} FROM ${table} WHERE ${where}", {
			columns = columns,
			table = table_name,
			where = where_clause_with_params
		})
		return self:query(query, unpack(values))
	else
		query = str.template("SELECT ${columns} FROM ${table}", {
			columns = columns,
			table = table_name
		})
		return self:query(query)
	end
end

-- Enhanced PostgreSQL schema helpers
function Connection:table_exists(table_name, schema_name)
	if str.is_blank(table_name) then
		return false
	end

	schema_name = schema_name or "public"
	local result = self:query_value(
		"SELECT tablename FROM pg_tables WHERE schemaname = $1 AND tablename = $2",
		str.trim(schema_name), str.trim(table_name)
	)
	return result ~= nil
end

function Connection:column_exists(table_name, column_name, schema_name)
	if str.is_blank(table_name) or str.is_blank(column_name) then
		return false
	end

	schema_name = schema_name or "public"
	local result = self:query_value([[
		SELECT column_name FROM information_schema.columns
		WHERE table_schema = $1 AND table_name = $2 AND column_name = $3
	]], str.trim(schema_name), str.trim(table_name), str.trim(column_name))
	return result ~= nil
end

function Connection:create_table(table_name, schema)
	if str.is_blank(table_name) or str.is_blank(schema) then
		error("Table name and schema cannot be empty")
	end

	local query = str.template("CREATE TABLE IF NOT EXISTS ${table} (${schema})", {
		table = table_name,
		schema = str.trim(schema)
	})
	return self:exec(query)
end

function Connection:drop_table(table_name, cascade)
	if str.is_blank(table_name) then
		error("Table name cannot be empty")
	end

	local cascade_clause = cascade and " CASCADE" or ""
	local query = str.template("DROP TABLE IF EXISTS ${table}${cascade}", {
		table = table_name,
		cascade = cascade_clause
	})
	return self:exec(query)
end

function Connection:add_column(table_name, column_def)
	if str.is_blank(table_name) or str.is_blank(column_def) then
		error("Table name and column definition cannot be empty")
	end

	local query = str.template("ALTER TABLE ${table} ADD COLUMN IF NOT EXISTS ${column}", {
		table = table_name,
		column = str.trim(column_def)
	})
	return self:exec(query)
end

function Connection:drop_column(table_name, column_name, cascade)
	if str.is_blank(table_name) or str.is_blank(column_name) then
		error("Table name and column name cannot be empty")
	end

	local cascade_clause = cascade and " CASCADE" or ""
	local query = str.template("ALTER TABLE ${table} DROP COLUMN IF EXISTS ${column}${cascade}", {
		table = table_name,
		column = column_name,
		cascade = cascade_clause
	})
	return self:exec(query)
end

function Connection:create_index(index_name, table_name, columns, unique, method)
	if str.is_blank(index_name) or str.is_blank(table_name) then
		error("Index name and table name cannot be empty")
	end

	local unique_clause = unique and "UNIQUE " or ""
	local method_clause = method and str.template(" USING ${method}", {method = str.upper(method)}) or ""
	local columns_str = type(columns) == "table" and tbl.concat(columns, ", ") or tostring(columns)

	local query = str.template("CREATE ${unique}INDEX IF NOT EXISTS ${index} ON ${table}${method} (${columns})", {
		unique = unique_clause,
		index = index_name,
		table = table_name,
		method = method_clause,
		columns = columns_str
	})
	return self:exec(query)
end

function Connection:drop_index(index_name, cascade)
	if str.is_blank(index_name) then
		error("Index name cannot be empty")
	end

	local cascade_clause = cascade and " CASCADE" or ""
	local query = str.template("DROP INDEX IF EXISTS ${index}${cascade}", {
		index = index_name,
		cascade = cascade_clause
	})
	return self:exec(query)
end

-- PostgreSQL-specific functions
function Connection:vacuum(table_name, analyze)
	local analyze_clause = analyze and " ANALYZE" or ""
	local table_clause = table_name and str.template(" ${table}", {table = table_name}) or ""
	return self:exec(str.template("VACUUM${analyze}${table}", {
		analyze = analyze_clause,
		table = table_clause
	}))
end

function Connection:analyze(table_name)
	local table_clause = table_name and str.template(" ${table}", {table = table_name}) or ""
	return self:exec(str.template("ANALYZE${table}", {table = table_clause}))
end

function Connection:reindex(name, type)
	if str.is_blank(name) then
		error("Name cannot be empty for REINDEX")
	end

	type = type or "INDEX"
	local valid_types = {"INDEX", "TABLE", "SCHEMA", "DATABASE", "SYSTEM"}
	local type_upper = str.upper(type)

	if not tbl.contains(valid_types, type_upper) then
		error(str.template("Invalid REINDEX type: ${type}", {type = type}))
	end

	return self:exec(str.template("REINDEX ${type} ${name}", {
		type = type_upper,
		name = name
	}))
end

-- PostgreSQL settings and introspection
function Connection:show(setting)
	if str.is_blank(setting) then
		error("Setting name cannot be empty")
	end
	return self:query_value(str.template("SHOW ${setting}", {setting = setting}))
end

function Connection:set(setting, value)
	if str.is_blank(setting) then
		error("Setting name cannot be empty")
	end
	return self:exec(str.template("SET ${setting} = ${value}", {
		setting = setting,
		value = tostring(value)
	}))
end

function Connection:current_database()
	return self:query_value("SELECT current_database()")
end

function Connection:current_schema()
	return self:query_value("SELECT current_schema()")
end

function Connection:version()
	return self:query_value("SELECT version()")
end

function Connection:list_schemas()
	return self:query("SELECT schema_name FROM information_schema.schemata ORDER BY schema_name")
end

function Connection:list_tables(schema_name)
	schema_name = schema_name or "public"
	return self:query("SELECT tablename FROM pg_tables WHERE schemaname = $1 ORDER BY tablename",
		str.trim(schema_name))
end

function Connection:describe_table(table_name, schema_name)
	if str.is_blank(table_name) then
		error("Table name cannot be empty")
	end

	schema_name = schema_name or "public"
	return self:query([[
		SELECT column_name, data_type, is_nullable, column_default
		FROM information_schema.columns
		WHERE table_schema = $1 AND table_name = $2
		ORDER BY ordinal_position
	]], str.trim(schema_name), str.trim(table_name))
end

-- JSON/JSONB helpers
function Connection:json_extract(column, path)
	if str.is_blank(column) or str.is_blank(path) then
		error("Column and path cannot be empty")
	end
	return str.template("${column}->'${path}'", {column = column, path = path})
end

function Connection:json_extract_text(column, path)
	if str.is_blank(column) or str.is_blank(path) then
		error("Column and path cannot be empty")
	end
	return str.template("${column}->>'${path}'", {column = column, path = path})
end

function Connection:jsonb_contains(column, value)
	if str.is_blank(column) or str.is_blank(value) then
		error("Column and value cannot be empty")
	end
	return str.template("${column} @> '${value}'", {column = column, value = value})
end

function Connection:jsonb_contained_by(column, value)
	if str.is_blank(column) or str.is_blank(value) then
		error("Column and value cannot be empty")
	end
	return str.template("${column} <@ '${value}'", {column = column, value = value})
end

-- Array helpers
function Connection:array_contains(column, value)
	if str.is_blank(column) then
		error("Column cannot be empty")
	end
	return str.template("$1 = ANY(${column})", {column = column})
end

function Connection:array_length(column)
	if str.is_blank(column) then
		error("Column cannot be empty")
	end
	return str.template("array_length(${column}, 1)", {column = column})
end

-- Connection management
function postgres.parse_dsn(dsn)
	if str.is_blank(dsn) then
		return nil, "DSN cannot be empty"
	end

	local parts = {}
	for pair in str.trim(dsn):gmatch("[^%s]+") do
		local key, value = pair:match("([^=]+)=(.+)")
		if key and value then
			parts[str.trim(key)] = str.trim(value)
		end
	end

	return parts
end

function postgres.connect(dsn)
	if str.is_blank(dsn) then
		error("DSN cannot be empty")
	end

	local conn_id = moonshark.sql_connect("postgres", str.trim(dsn))
	if conn_id then
		local conn = {_id = conn_id}
		setmetatable(conn, Connection)
		return conn
	end
	return nil
end

postgres.open = postgres.connect

-- Quick execution functions
function postgres.query(dsn, query_str, ...)
	local conn = postgres.connect(dsn)
	if not conn then
		error("Failed to connect to PostgreSQL database")
	end

	local results = conn:query(query_str, ...)
	conn:close()
	return results
end

function postgres.exec(dsn, query_str, ...)
	local conn = postgres.connect(dsn)
	if not conn then
		error("Failed to connect to PostgreSQL database")
	end

	local result = conn:exec(query_str, ...)
	conn:close()
	return result
end

function postgres.query_row(dsn, query_str, ...)
	local results = postgres.query(dsn, query_str, ...)
	if results and #results > 0 then
		return results[1]
	end
	return nil
end

function postgres.query_value(dsn, query_str, ...)
	local row = postgres.query_row(dsn, query_str, ...)
	if row then
		for _, value in pairs(row) do
			return value
		end
	end
	return nil
end

-- Migration helpers
function postgres.migrate(dsn, migrations, schema)
	schema = schema or "public"
	local conn = postgres.connect(dsn)
	if not conn then
		error("Failed to connect to PostgreSQL database for migration")
	end

	conn:create_table("_migrations",
		"id SERIAL PRIMARY KEY, name TEXT UNIQUE NOT NULL, applied_at TIMESTAMPTZ DEFAULT NOW()")

	local tx = conn:begin()
	if not tx then
		conn:close()
		error("Failed to begin migration transaction")
	end

	local success = true
	local error_msg = ""

	for _, migration in ipairs(migrations) do
		if not migration.name or str.is_blank(migration.name) then
			error_msg = "Migration must have a non-empty name"
			success = false
			break
		end

		local existing = conn:query_value("SELECT id FROM _migrations WHERE name = $1",
			str.trim(migration.name))
		if not existing then
			local ok, err = pcall(function()
				if type(migration.up) == "string" then
					conn:exec(migration.up)
				elseif type(migration.up) == "function" then
					migration.up(conn)
				else
					error("Migration 'up' must be string or function")
				end
			end)

			if ok then
				conn:exec("INSERT INTO _migrations (name) VALUES ($1)", str.trim(migration.name))
				print(str.template("Applied migration: ${name}", {name = migration.name}))
			else
				success = false
				error_msg = str.template("Migration '${name}' failed: ${error}", {
					name = migration.name,
					error = err or "unknown error"
				})
				break
			end
		end
	end

	if success then
		tx:commit()
	else
		tx:rollback()
		conn:close()
		error(error_msg)
	end

	conn:close()
	return true
end

-- Simplified result processing utilities
function postgres.to_array(results, column_name)
	if not results or tbl.is_empty(results) then
		return {}
	end

	if str.is_blank(column_name) then
		error("Column name cannot be empty")
	end

	return tbl.map(results, function(row) return row[column_name] end)
end

function postgres.to_map(results, key_column, value_column)
	if not results or tbl.is_empty(results) then
		return {}
	end

	if str.is_blank(key_column) then
		error("Key column name cannot be empty")
	end

	local map = {}
	for _, row in ipairs(results) do
		local key = row[key_column]
		map[key] = value_column and row[value_column] or row
	end
	return map
end

function postgres.group_by(results, column_name)
	if not results or tbl.is_empty(results) then
		return {}
	end

	if str.is_blank(column_name) then
		error("Column name cannot be empty")
	end

	return tbl.group_by(results, function(row) return row[column_name] end)
end

-- Simplified debug helper
function postgres.print_results(results)
	if not results or tbl.is_empty(results) then
		print("No results")
		return
	end

	local columns = tbl.keys(results[1])
	tbl.sort(columns)

	-- Calculate column widths
	local widths = {}
	for _, col in ipairs(columns) do
		widths[col] = str.length(col)
	end

	for _, row in ipairs(results) do
		for _, col in ipairs(columns) do
			local value = tostring(row[col] or "")
			widths[col] = math.max(widths[col], str.length(value))
		end
	end

	-- Print header
	local header_parts = tbl.map(columns, function(col) return str.pad_right(col, widths[col]) end)
	local separator_parts = tbl.map(columns, function(col) return str.repeat_("-", widths[col]) end)

	print(tbl.concat(header_parts, " | "))
	print(tbl.concat(separator_parts, "-+-"))

	-- Print rows
	for _, row in ipairs(results) do
		local value_parts = tbl.map(columns, function(col)
			local value = tostring(row[col] or "")
			return str.pad_right(value, widths[col])
		end)
		print(tbl.concat(value_parts, " | "))
	end
end

function postgres.escape_identifier(name)
	if str.is_blank(name) then
		error("Identifier name cannot be empty")
	end
	return str.template('"${name}"', {name = str.replace(name, '"', '""')})
end

function postgres.escape_literal(value)
	if type(value) == "string" then
		return str.template("'${value}'", {value = str.replace(value, "'", "''")})
	end
	return tostring(value)
end

return postgres